Journal articles on the topic 'Orientation/direction selectivity'
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Gizzi, M. S., E. Katz, R. A. Schumer, and J. A. Movshon. "Selectivity for orientation and direction of motion of single neurons in cat striate and extrastriate visual cortex." Journal of Neurophysiology 63, no. 6 (June 1, 1990): 1529–43. http://dx.doi.org/10.1152/jn.1990.63.6.1529.
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1. We consider the consequences of the orientation selectivity shown by most cortical neurons for the nature of the signals they can convey about the direction of stimulus movement. On theoretical grounds we distinguish component direction selectivity, in which cells are selective for the direction of movement of oriented components of a complex stimulus, from pattern direction selectivity, or selectivity for the overall direction of movement of a pattern irrespective of the directions of its components. We employed a novel test using grating and plaid targets to distinguish these forms of direction selectivity. 2. We studied the responses of 280 cells from the striate cortex and 107 cells from the lateral suprasylvian cortex (LS) to single sinusoidal gratings to determine their orientation preference and directional selectivity. We tested 73 of these with sinusoidal plaids, composed of two sinusoidal gratings at different orientations, to study the organization of the directional mechanisms within the receptive field. 3. When tested with single gratings, the directional tuning of 277 oriented cells in area 17 had a mean half width of 20.6 degrees, a mode near 13 degrees, and a range of 3.8-58 degrees. Simple cells were slightly more narrowly tuned than complex cells. The selectivity of LS neurons for the direction of moving gratings is not markedly different from that of neurons in area 17. The mean direction half width was 20.7 degrees. 4. We evaluated the directional selectivity of these neurons by comparing responses to stimuli moved in the optimal direction with those elicited by a stimulus moving in the opposite direction. In area 17 about two-thirds of the neurons responded less than half as well to the non-preferred direction as to the preferred direction; two-fifths of the units responded less than one-fifth as well. Complex cells showed a somewhat greater tendency to directional bias than simple cells. LS neurons tended to have stronger directional asymmetries in their response to moving gratings: 83% of LS neurons showed a significant directional asymmetry. 5. Neurons in both areas responded independently to each component of the plaid. Thus cells giving single-lobed directional-tuning curves to gratings showed bilobed plaid tuning curves, with each lobe corresponding to movement in an effective direction by one of the two component gratings within the plaid. The two best directions for the plaids were those at which one or other single grating would have produced an optimal response when presented alone.(ABSTRACT TRUNCATED AT 400 WORDS)
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Chaudhuri, Avi, and Thomas D. Albright. "Neuronal responses to edges defined by luminance vs. temporal texture in macaque area V1." Visual Neuroscience 14, no. 5 (September 1997): 949–62. http://dx.doi.org/10.1017/s0952523800011664.
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AbstractWe examined the responsivity, orientation selectivity, and direction selectivity of a sample of neurons in cortical area V1 of the macaque using visual stimuli consisting of drifting oriented contours defined by each of two very different figural cues: luminance contrast and temporal texture. Comparisons of orientation and direction tuning elicited by the different cues were made in order to test the hypothesis that the neuronal representations of these parameters are form-cue invariant. The majority of the sampled cells responded to both stimulus types, although responses to temporal texture stimuli were generally weaker than those elicited by luminance-defined stimuli. Of those units exhibiting orientation selectivity when tested with the luminance-defined stimuli, more than half were also selective for the orientation of the temporal texture stimuli. There was close correspondence between the preferred orientations and tuning bandwidths revealed with the two stimulus types. Of those units exhibiting directional selectivity when tested with the luminance-defined stimuli, about two-thirds were also selective for the direction of the temporal texture stimuli. There was close correspondence between the preferred directions revealed with the two stimulus types, although bidirectional responses were somewhat more common when temporal texture stimuli were used. These results indicate that many V1 neurons encode orientation and direction of motion of retinal image features in a manner that is largely independent of whether the feature is defined by luminance or temporal texture contrast. These neurons may contribute to perceptual phenomena in which figural cue identity is disregarded.
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Crook, John M., Zoltan F. Kisvárday, and Ulf T. Eysel. "GABA-induced inactivation of functionally characterized sites in cat striate cortex: Effects on orientation tuning and direction selectivity." Visual Neuroscience 14, no. 1 (January 1997): 141–58. http://dx.doi.org/10.1017/s095252380000883x.
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AbstractMicroiontophoresis of γ-aminobutyric acid (GABA) was used to reversibly inactivate small sites of defined orientation/direction specificity in layers II-IV of cat area 17 while single cells were recorded in the same area at a horizontal distance of ~350–700 jam. We compared the effect of inactivating iso-orientation sites (where orientation preference was within 22.5 deg) and cross-orientation sites (where it differed by 45–90 deg) on orientation tuning and directionality. The influence of iso-orientation inactivation was tested in 33 cells, seven of which were subjected to alternate inactivation of two iso-orientation sites with opposite direction preference. Of the resulting 40 inactivations, only two (5%) caused significant changes in orientation tuning, whereas 26 (65%) elicited effects on directionality: namely, an increase or a decrease in response to a cell's preferred direction when its direction preference was the same as that at an inactivation site, and an increase in response to a cell's nonpreferred direction when its direction preference was opposite that at an inactivation site. It is argued that the decreases in response to the preferred direction reflected a reduction in the strength of intracortical iso-orientation excitatory connections, while the increases in response were due to the loss of iso-orientation inhibition. Of 35 cells subjected to cross-orientation inactivation, only six (17%) showed an effect on directionality, whereas 21 (60%) showed significant broadening of orientation tuning, with an increase in mean tuning width at half-height of 126%. The effects on orientation tuning were due to increases in response to nonoptimal orientations. Changes in directionality also resulted from increased responses (to preferred or nonpreferred directions) and were always accompanied by broadening of tuning. Thus, the effects of cross-orientation inactivation were presumably due to the loss of a cross-orientation inhibitory input that contributes mainly to orientation tuning by suppressing responses to nonoptimal orientations. Differential effects of iso-orientation and cross-orientation inactivation could be elicited in the same cell or in different cells from the same inactivation site. The results suggest the involvement of three different intracortical processes in the generation of orientation tuning and direction selectivity in area 17: (1) suppression of responses to nonoptimal orientations and directions as a result of cross-orientation inhibition and iso-orientation inhibition between cells with opposite direction preferences; (2) amplification of responses to optimal stimuli via iso-orientation excitatory connections; and (3) regulation of cortical amplification via iso-orientation inhibition.
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MURTHY, A., A. L. HUMPHREY, A. B. SAUL, and J. C. FEIDLER. "Laminar differences in the spatiotemporal structure of simple cell receptive fields in cat area 17." Visual Neuroscience 15, no. 2 (February 1998): 239–56. http://dx.doi.org/10.1017/s0952523898152045.
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Previous studies of cat visual cortex have shown that the spatiotemporal (S-T) structure of simple cell receptive fields correlates with direction selectivity. However, great heterogeneity exists in the relationship and this has implications for models. Here we report a laminar basis for some of the heterogeneity. S-T structure and direction selectivity were measured in 101 cells using stationary counterphasing and drifting gratings, respectively. Two procedures were used to assess S-T structure and its relation to direction selectivity. In the first, the S-T orientations of receptive fields were quantified by fitting response temporal phase versus stimulus spatial phase data. In the second procedure, conventional linear predictions of direction selectivity were computed from the amplitudes and phases of responses to stationary gratings. Extracellular recording locations were reconstructed histologically. Among direction-selective cells, S-T orientation was greatest in layer 4B and it correlated well (r = 0.76) with direction selectivity. In layer 6, S-T orientation was uniformly low, overlapping little with layer 4B, and it was not correlated with directional tuning. Layer 4A was intermediate in S-T orientation and its relation (r = 0.46) to direction selectivity. The same laminar patterns were observed using conventional linear predictions. The patterns do not reflect laminar differences in direction selectivity since the layers were equivalent in directional tuning. We also evaluated a model of linear spatiotemporal summation followed by a static nonlinear amplification (exponent model) to account for direction selectivity. The values of the exponents were estimated from differences between linearly predicted and actual amplitude modulations to counterphasing gratings. Comparing these exponents with another exponent—that required to obtain perfect matches between linearly predicted and measured directional tuning—indicates that an exponent model largely accounts for direction selectivity in most cells in layer 4, particularly layer 4B, but not in layer 6. Dynamic nonlinearities seem essential for cells in layer 6. We suggest that these laminar differences may partly reflect the differential involvement of geniculocortical and intracortical mechanisms.
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Crook, J. M., Z. F. Kisvarday, and U. T. Eysel. "GABA-induced inactivation of functionally characterized sites in cat visual cortex (area 18): effects on direction selectivity." Journal of Neurophysiology 75, no. 5 (May 1, 1996): 2071–88. http://dx.doi.org/10.1152/jn.1996.75.5.2071.
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1. Microiontophoresis of gamma-aminobutyric acid was used to reversibly inactivate small sites of defined orientation and direction specificity at a horizontal distance of 400-700 microns from single cells recorded in cat area 18. There was extensive or complete overlap between the receptive fields of cells at the recording and inactivation sites. A cell's directionality index [DI: 1 - (response to nonpreferred direction/response to preferred direction)], the response to the preferred direction, and orientation tuning width (measured at half the maximum response) were compared before and during inactivation of either iso-orientation sites (where the orientation preference was within 22.5 degrees) or cross-orientation sites (where it differed by 45-90 degrees). 2. During iso-orientation inactivation, 40 (73%) of 55 cells showed a significant (> 0.20) change in DI; the mean change in DI for these cells was 0.59. An additional cell showed a marked increase in response to the preferred direction that did not result in a change in DI. With one exception, the effects occurred in the absence of a significant (> 25%) change in orientation tuning width. 3. In most cases, the results were broadly predictable in the sense that iso-orientation inactivation predominantly affected a cell's response to the direction of motion of an optimally oriented bar that was closest to the preferred direction at the inactivation site: viz., a decrease in response to the preferred direction and an increase in response to the preferred or nonpreferred direction. 4. It is argued that the decreases in response were due to a reduction in the strength of intracortical iso-orientation excitatory connections made primarily between cells with similar direction preferences, whereas the increases in response involved a loss of iso-orientation inhibition. 5. In cases where remote inactivation caused an increase in response to the nonpreferred direction, comparable effects could be elicited when a mask left exposed only the excitatory subregion of the receptive field in S cells or the most responsive part of the excitatory discharge region in C cells. This implies extensive or complete spatial overlap between the profiles of excitation and inhibition in a cell's nonpreferred direction. 6. During cross-orientation inactivation, a significant change in DI was seen in only 14 (19%) of 73 cells and, with one exception, these changes were accompanied by increases in response to non-optimal orientations and significant broadening of orientation tuning. The effects of cross-orientation inactivation on directionality were presumably due to the loss of cross-orientation inhibition, which contributes primarily to orientation tuning. 7. Inactivation of the same site could cause an increase in response to the nonpreferred direction in cells recorded at iso-orientation sites and an increase in response to nonoptimal orientations and broadening of orientation tuning in cells recorded at cross-orientation sites. This is consistent with the notion that a single inhibitory neuron can contribute to the directionality or orientation tuning of different target cells depending on their location in the orientation map. 8. The results provide evidence for a major contribution of intrinsic mechanisms to the orientation tuning and direction selectivity of cells in cat area 18. It is proposed that two different intracortical processes are involved in the enhancement of orientation and direction selectivity: 1) suppression of responses to nonoptimal orientations and directions as a result of cross-orientation inhibition and iso-orientation inhibition; and 2) facilitation of responses to optimal orientations/directions via iso-orientation excitatory connections.
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Chen, Hui, Xiaorong Liu, and Ning Tian. "Subtype-dependent postnatal development of direction- and orientation-selective retinal ganglion cells in mice." Journal of Neurophysiology 112, no. 9 (November 1, 2014): 2092–101. http://dx.doi.org/10.1152/jn.00320.2014.
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The direction-selective ganglion cells (DSGCs) and orientation-selective ganglion cells (OSGCs) encode the directional and the orientational information of a moving object, respectively. It is unclear how DSGCs and OSGCs mature in the mouse retina during postnatal development. Here we investigated the development of DSGCs and OSGCs after eye-opening. We show that 1) DSGCs and OSGCs are present at postnatal day 12 (P12), just before eye-opening; 2) the fractions of both DSGCs and OSGCs increase from P12 to P30; 3) the development of DSGCs and OSGCs is subtype dependent; and 4) direction and orientation selectivity are two separate features of retinal ganglion cells (RGCs) in the mouse retina. We classified RGCs into different functional subtypes based on their light response properties. Compared with P12, the direction and orientation selectivity of ON-OFF RGCs but not ON RGCs became stronger at P30. The tuning width of DSGCs for both ON and ON-OFF subtypes decreased with age. For OSGCs, we divided them into non-direction-selective (non-DS) OSGCs and direction-selective OSGCs (DS&OSGCs). For DS&OSGCs, we found that there was no correlation between the direction and orientation selectivity, and that the tuning width of both ON and ON-OFF subtypes remained unchanged with age. For non-DS OSGCs, the tuning width of ON but not ON-OFF subtype decreased with development. These findings provide a foundation to reveal the molecular and synaptic mechanisms underlying the development of the direction and orientation selectivity in the retina.
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Zaltsman, Julia B., J. Alexander Heimel, and Stephen D. Van Hooser. "Weak orientation and direction selectivity in lateral geniculate nucleus representing central vision in the gray squirrelSciurus carolinensis." Journal of Neurophysiology 113, no. 7 (April 2015): 2987–97. http://dx.doi.org/10.1152/jn.00516.2014.
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Classic studies of lateral geniculate nucleus (LGN) and visual cortex (V1) in carnivores and primates have found that a majority of neurons in LGN exhibit a center-surround organization, while V1 neurons exhibit strong orientation selectivity and, in many species, direction selectivity. Recent work in the mouse and the monkey has discovered previously unknown classes of orientation- and direction-selective neurons in LGN. Furthermore, some recent studies in the mouse report that many LGN cells exhibit pronounced orientation biases that are of comparable strength to the subthreshold inputs to V1 neurons. These results raise the possibility that, in rodents, orientation biases of individual LGN cells make a substantial contribution to cortical orientation selectivity. Alternatively, the size and contribution of orientation- or direction-selective channels from LGN to V1 may vary across mammals. To address this question, we examined orientation and direction selectivity in LGN and V1 neurons of a highly visual diurnal rodent: the gray squirrel. In the representation of central vision, only a few LGN neurons exhibited strong orientation or direction selectivity. Across the population, LGN neurons showed weak orientation biases and were much less selective for orientation compared with V1 neurons. Although direction selectivity was weak overall, LGN layers 3abc, which contain neurons that express calbindin, exhibited elevated direction selectivity index values compared with LGN layers 1 and 2. These results suggest that, for central visual fields, the contribution of orientation- and direction-selective channels from the LGN to V1 is small in the squirrel. As in other mammals, this small contribution is elevated in the calbindin-positive layers of the LGN
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Hammond, P., and J. N. Kim. "Role of suppression in shaping orientation and direction selectivity of complex neurons in cat striate cortex." Journal of Neurophysiology 75, no. 3 (March 1, 1996): 1163–76. http://dx.doi.org/10.1152/jn.1996.75.3.1163.
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1. Single binocularly driven complex neurons in cat striate cortex were recorded extracellularly under nitrous oxide-oxygen-halothane anesthesia and muscle relaxant. Orientational/directional tuning was initially derived for each eye in turn, with sine wave gratings of optimal spatial frequency and velocity, while the other eye viewed a uniform field. 2. For the dominant eye, previously concealed suppression was revealed against elevated levels of firing induced with a conditioning grating, drifting continuously in the preferred direction, simultaneously presented to the nondominant eye. During steady-state binocular conditioning, orientational/directional tuning was reestablished for the dominant eye. In a subset of cells, tuning curves during conditioning were also derived for the reverse configuration, i.e., nondominant eye tuning, dominant eye conditioning: results were qualitatively identical to those for conditioning through the nondominant eye. 3. Neurons were initially segregated into five groups, according to the observed suppression profiles induced at nonoptimal orientations/directions during conditioning: Type 1, suppression centered on orthogonal directions; Type 2, suppression around null directions; Type 3, null suppression combined with orthogonal suppression; Type 4, lateral suppression, maximal for directions immediately flanking those inducing excitation; and Type 5, the residue of cells, totally lacking suppression or showing complex or variable suppression. 4. Sharpness of (excitatory) tuning was correlated with directionality and with class of suppression revealed during binocular conditioning. Direction-biased neurons were more sharply orientation tuned than direction-selective neurons; similarly, neurons exhibiting lateral or orthogonal suppression during conditioning were more sharply tuned than neurons with null suppression. 5. Application of suboptimal directions of conditioning weakened the induced suppression but altered none of its main characteristics. 6. The relationship between excitation, suppression, and spatial frequency was investigated by comparing tuning curves for the dominant eye at several spatial frequencies, without and during conditioning. End-stopped neurons preferred lower spatial frequencies and higher velocities of motion than non-end-stopped neurons. Confirming previous reports, suppression in some neurons was still present for spatial frequencies above the cutoff frequency for excitation, demonstrating the tendency for suppression to be more broadly spatial frequency tuned than excitation. 7. Scatterplots of strength of suppression, in directions orthogonal and opposite maximal excitation, partially segregated neurons of Types 1-3. Clearer segregation of Types 1-4 was obtained by curve-fitting to profiles of suppression, and correlating half-width of tuning for suppression with the angle between the directions of optimal suppression and optimal excitation in each neuron. 8. Two interpretations are advanced-the first, based on three discrete classes of inhibition, orthogonal, null and lateral; the second, based on only two classes, orthogonal and null/lateral--in which null and lateral suppression are manifestations of the same inhibitory mechanism operating, respectively, on broadly tuned direction-selective or on sharply tuned direction-biased neurons. Orthogonal suppression may be untuned for direction, whereas lateral and null suppression are broadly direction tuned. Within each class, suppression is more broadly spatial frequency tuned than excitation. 9. It is concluded that orientational/directional selectivity of complex cells at different spatial frequencies is determined by the balance between tuned excitation and varying combinations of relatively broadly distributed or untuned inhibition.
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Murase, Sachiko, Sarah E. Robertson, Crystal L. Lantz, Ji Liu, Daniel E. Winkowski, and Elizabeth M. Quinlan. "Chronic Monocular Deprivation Reveals MMP9-Dependent and -Independent Aspects of Murine Visual System Plasticity." International Journal of Molecular Sciences 23, no. 5 (February 23, 2022): 2438. http://dx.doi.org/10.3390/ijms23052438.
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The deletion of matrix metalloproteinase MMP9 is combined here with chronic monocular deprivation (cMD) to identify the contributions of this proteinase to plasticity in the visual system. Calcium imaging of supragranular neurons of the binocular region of primary visual cortex (V1b) of wild-type mice revealed that cMD initiated at eye opening significantly decreased the strength of deprived-eye visual responses to all stimulus contrasts and spatial frequencies. cMD did not change the selectivity of V1b neurons for the spatial frequency, but orientation selectivity was higher in low spatial frequency-tuned neurons, and orientation and direction selectivity were lower in high spatial frequency-tuned neurons. Constitutive deletion of MMP9 did not impact the stimulus selectivity of V1b neurons, including ocular preference and tuning for spatial frequency, orientation, and direction. However, MMP9−/− mice were completely insensitive to plasticity engaged by cMD, such that the strength of the visual responses evoked by deprived-eye stimulation was maintained across all stimulus contrasts, orientations, directions, and spatial frequencies. Other forms of experience-dependent plasticity, including stimulus selective response potentiation, were normal in MMP9−/− mice. Thus, MMP9 activity is dispensable for many forms of activity-dependent plasticity in the mouse visual system, but is obligatory for the plasticity engaged by cMD.
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Berman, N. E., M. E. Wilkes, and B. R. Payne. "Organization of orientation and direction selectivity in areas 17 and 18 of cat cerebral cortex." Journal of Neurophysiology 58, no. 4 (October 1, 1987): 676–99. http://dx.doi.org/10.1152/jn.1987.58.4.676.
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1. The organization of subunits and sequences subserving preferred stimulus orientation and preferred direction of stimulus motion in cat cerebral cortical areas 17 and 18 was determined by making vertical, tangential, and oblique microelectrode penetrations into those areas. 2. Quantitative measurements of direction selectivity indicated that not all shades of direction selectivity are equally represented in area 17. Peaks in the distribution of direction indices may correspond to the bidirectional, direction biased, and direction selective categories used in qualitative studies. 3. The relationship between preferred direction and location in the visual field was examined for units with receptive fields centered more than 15 degrees from the area centralis. Simple cells had orientation preferences that tended to be parallel to radii extending out from the area centralis. Wide-field complex cells had orientation preferences that tended to be parallel to concentric circles centered on the area centralis; the direction preferences of this group were biased toward motion away from the area centralis. 4. Unit pairs separated by 200 microns or less were 4.2 times as likely to have the same preferred direction as to have opposite preferred directions, indicating that, on average, strings of five neurons have similar direction preferences. 5. Tracks in area 18 showed a similar pattern to those in area 17. 6. In the vertical tracks in area 17 a small proportion (12%) of the units recorded in infragranular layers had preferred orientations that deviated 30 degrees or more from the first unit recorded in the same column. The presence of these cells most likely reflects the relative crowding of columns in infragranular layers, which occurs at the crown of the lateral gyrus. Columns with such large jumps in preferred orientation were not observed in area 18, which occupies a relatively flat region of cortex. 7. In both areas 17 and 18 direction preference in vertical tracks usually reversed at least once, either between supra- and infragranular layers or within infragranular layers. Along these same tracks, orientation preference usually did not change. 8. In tangential tracks, preferred direction and orientation preferences changed together in small increments. Occasionally a large jump in preferred direction would occur with only a small change in preferred orientation. These large jumps were considered to mark the boundaries of the direction sequences. Most frequently these boundaries were separated by 400-600 microns. This value is approximately half the size of a complete set of orientation preferences (700-1,200 microns).(ABSTRACT TRUNCATED AT 400 WORDS)
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Wörgötter, Florentin, Ernst Niebur, and Christof Koch. "Generation of Direction Selectivity by Isotropic Intracortical Connections." Neural Computation 4, no. 3 (May 1992): 332–40. http://dx.doi.org/10.1162/neco.1992.4.3.332.
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To what extent do the mechanisms generating different receptive field properties of neurons depend on each other? We investigated this question theoretically within the context of orientation and direction tuning of simple cells in the mammalian visual cortex. In our model a cortical cell of the "simple" type receives its orientation tuning by afferent convergence of aligned receptive fields of the lateral geniculate nucleus (Hubel and Wiesel 1962). We sharpen this orientation bias by postulating a special type of radially symmetric long-range lateral inhibition called circular inhibition. Surprisingly, this isotropic mechanism leads to the emergence of a strong bias for the direction of motion of a bar. We show that this directional anisotropy is neither caused by the probabilistic nature of the connections nor is it a consequence of the specific columnar structure chosen but that it is an inherent feature of the architecture of visual cortex.
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Murthy, Aditya, and Allen L. Humphrey. "Inhibitory Contributions to Spatiotemporal Receptive-Field Structure and Direction Selectivity in Simple Cells of Cat Area 17." Journal of Neurophysiology 81, no. 3 (March 1, 1999): 1212–24. http://dx.doi.org/10.1152/jn.1999.81.3.1212.
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Inhibitory contributions to spatiotemporal receptive-field structure and direction selectivity in simple cells of cat area 17. Intracortical inhibition contributes to direction selectivity in primary visual cortex, but how it acts has been unclear. We investigated this problem in simple cells of cat area 17 by taking advantage of the link between spatiotemporal (S-T) receptive-field structure and direction selectivity. Most cells in layer 4 have S-T–oriented receptive fields in which gradients of response timing across the field confer a preferred direction of motion. Linear summation of responses across the receptive field, followed by a static nonlinear amplification, has been shown previously to account for directional tuning in layer 4. We tested the hypotheses that inhibition acts by altering S-T structure or the static nonlinearity or both. Drifting and counterphasing sinewave gratings were used to measure direction selectivity and S-T structure, respectively, in 17 layer 4 simple cells before and during iontophoresis of bicuculline methiodide (BMI), a GABAA antagonist. S-T orientation was quantified from fits to response temporal phase versus stimulus spatial phase data. Bicuculline reduced direction selectivity and S-T orientation in nearly all cells, and reductions in the two measures were well correlated ( r = 0.81) and reversible. Using conventional linear predictions based on response phase and amplitude, we found that BMI-induced changes in S-T structure also accounted well for absolute changes in the amplitude and phase of responses to gratings drifting in the preferred and nonpreferred direction. For each cell we also calculated an exponent used to estimate the static nonlinearity. Bicuculline reduced the exponent in most cells, but the changes were not correlated with reductions in direction selectivity. We conclude that GABAA-mediated inhibition influences directional tuning in layer 4 primarily by sculpting S-T receptive-field structure. The source of the inhibition is likely to be other simple cells with certain spatiotemporal relationships to their target. Despite reductions in the two measures, most receptive fields maintained some directional tuning and S-T orientation during BMI. This suggests that their excitatory inputs, arising from the lateral geniculate nucleus and within area 17, are sufficient to create some S-T orientation and that inhibition accentuates it. Finally, BMI also reduced direction selectivity in 8 of 10 simple cells tested in layer 6, but the reductions were not accompanied by systematic changes in S-T structure. This reflects the fact that S-T orientation, as revealed by our first-order measures of the receptive field, is weak there normally. Inhibition likely affects layer 6 cells via more complex, nonlinear interactions.
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Blais, Brian, Leon N. Cooper, and Harel Shouval. "Formation of Direction Selectivity in Natural Scene Environments." Neural Computation 12, no. 5 (May 1, 2000): 1057–66. http://dx.doi.org/10.1162/089976600300015501.
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Most simple and complex cells in the cat striate cortex are both orientation and direction selective. In this article we use single-cell learning rules to develop both orientation and direction selectivity in a natural scene environment. We show that a simple principal component analysis rule is inadequate for developing direction selectivity, but that the BCM rule as well as similar higher-order rules can. We also demonstrate that the convergence of lagged and nonlagged cells depends on the velocity of motion in the environment, and that strobe rearing disrupts this convergence, resulting in a loss of direction selectivity.
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Moore, Bartlett D., Henry J. Alitto, and W. Martin Usrey. "Orientation Tuning, But Not Direction Selectivity, Is Invariant to Temporal Frequency in Primary Visual Cortex." Journal of Neurophysiology 94, no. 2 (August 2005): 1336–45. http://dx.doi.org/10.1152/jn.01224.2004.
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The activity of neurons in primary visual cortex is influenced by the orientation, contrast, and temporal frequency of a visual stimulus. This raises the question of how these stimulus properties interact to shape neuronal responses. While past studies have shown that the bandwidth of orientation tuning is invariant to stimulus contrast, the influence of temporal frequency on orientation-tuning bandwidth is unknown. Here, we investigate the influence of temporal frequency on orientation tuning and direction selectivity in area 17 of ferret visual cortex. For both simple cells and complex cells, measures of orientation-tuning bandwidth (half-width at half-maximum response) are ∼20–25° across a wide range of temporal frequencies. Thus cortical neurons display temporal-frequency invariant orientation tuning. In contrast, direction selectivity is typically reduced, and occasionally reverses, at nonpreferred temporal frequencies. These results show that the mechanisms contributing to the generation of orientation tuning and direction selectivity are differentially affected by the temporal frequency of a visual stimulus and support the notion that stability of orientation tuning is an important aspect of visual processing.
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Olavarria, J. F., E. A. DeYoe, J. J. Knierim, J. M. Fox, and D. C. van Essen. "Neural responses to visual texture patterns in middle temporal area of the macaque monkey." Journal of Neurophysiology 68, no. 1 (July 1, 1992): 164–81. http://dx.doi.org/10.1152/jn.1992.68.1.164.
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1. We studied how neurons in the middle temporal visual area (MT) of anesthetized macaque monkeys responded to textured and nontextured visual stimuli. Stimuli contained a central rectangular ,figure- that was either uniform in luminance or consisted of an array of oriented line segments. The figure moved at constant velocity in one of four orthogonal directions. The region surrounding the figure was either uniform in luminance or contained a texture array (whose elements were identical or orthogonal in orientation to those of the figure), and it either was stationary or moved along with the figure. 2. A textured figure moving across a stationary textured background (,texture bar- stimulus) often elicited vigorous neural responses, but, on average, the responses to texture bars were significantly smaller than to solid (uniform luminance) bars. 3. Many cells showed direction selectivity that was similar for both texture bars and solid bars. However, on average, the direction selectivity measured when texture bars were used was significantly smaller than that for solid bars, and many cells lost significant direction selectivity altogether. The reduction in direction selectivity for texture bars generally reflected a combination of decreased responsiveness in the preferred direction and increased responsiveness in the null (opposite to preferred) direction. 4. Responses to a texture bar in the absence of a texture background (,texture bar alone-) were very similar to the responses to solid bars both in the magnitude of response and in the degree of direction selectivity. Conversely, adding a static texture surround to a moving solid bar reduced direction selectivity on average without a reduction in response magnitude. These results indicate that the static surround is largely responsible for the differences in direction selectivity for texture bars versus solid bars. 5. In the majority of MT cells studied, responses to a moving texture bar were largely independent of whether the elements in the bar were of the same orientation as the background elements or of the orthogonal orientation. Thus, for the class of stimuli we used, orientation contrast does not markedly affect the responses of MT neurons to moving texture patterns. 6. The optimum figure length and the shapes of the length tuning curves determined with the use of solid bars and texture bars differed significantly in most of the cells examined. Thus neurons in MT are not simply selective for a particular figure shape independent of whatever cues are used to delineate the figure.
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Hollmann, Vanessa, Valerie Lucks, Rafael Kurtz, and Jacob Engelmann. "Adaptation-induced modification of motion selectivity tuning in visual tectal neurons of adult zebrafish." Journal of Neurophysiology 114, no. 5 (November 1, 2015): 2893–902. http://dx.doi.org/10.1152/jn.00568.2015.
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In the developing brain, training-induced emergence of direction selectivity and plasticity of orientation tuning appear to be widespread phenomena. These are found in the visual pathway across different classes of vertebrates. Moreover, short-term plasticity of orientation tuning in the adult brain has been demonstrated in several species of mammals. However, it is unclear whether neuronal orientation and direction selectivity in nonmammalian species remains modifiable through short-term plasticity in the fully developed brain. To address this question, we analyzed motion tuning of neurons in the optic tectum of adult zebrafish by calcium imaging. In total, orientation and direction selectivity was enhanced by adaptation, responses of previously orientation-selective neurons were sharpened, and even adaptation-induced emergence of selectivity in previously nonselective neurons was observed in some cases. The different observed effects are mainly based on the relative distance between the previously preferred and the adaptation direction. In those neurons in which a shift of the preferred orientation or direction was induced by adaptation, repulsive shifts (i.e., away from the adapter) were more prevalent than attractive shifts. A further novel finding for visually induced adaptation that emerged from our study was that repulsive and attractive shifts can occur within one brain area, even with uniform stimuli. The type of shift being induced also depends on the difference between the adapting and the initially preferred stimulus direction. Our data indicate that, even within the fully developed optic tectum, short-term plasticity might have an important role in adjusting neuronal tuning functions to current stimulus conditions.
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Scholl, Benjamin, Johnathan Rylee, Jeffrey J. Luci, Nicholas J. Priebe, and Jeffrey Padberg. "Orientation selectivity in the visual cortex of the nine-banded armadillo." Journal of Neurophysiology 117, no. 3 (March 1, 2017): 1395–406. http://dx.doi.org/10.1152/jn.00851.2016.
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Orientation selectivity in primary visual cortex (V1) has been proposed to reflect a canonical computation performed by the neocortical circuitry. Although orientation selectivity has been reported in all mammals examined to date, the degree of selectivity and the functional organization of selectivity vary across mammalian clades. The differences in degree of orientation selectivity are large, from reports in marsupials that only a small subset of neurons are selective to studies in carnivores, in which it is rare to find a neuron lacking selectivity. Furthermore, the functional organization in cortex varies in that the primate and carnivore V1 is characterized by an organization in which nearby neurons share orientation preference while other mammals such as rodents and lagomorphs either lack or have only extremely weak clustering. To gain insight into the evolutionary emergence of orientation selectivity, we examined the nine-banded armadillo, a species within the early placental clade Xenarthra. Here we use a combination of neuroimaging, histological, and electrophysiological methods to identify the retinofugal pathways, locate V1, and for the first time examine the functional properties of V1 neurons in the armadillo ( Dasypus novemcinctus) V1. Individual neurons were strongly sensitive to the orientation and often the direction of drifting gratings. We uncovered a wide range of orientation preferences but found a bias for horizontal gratings. The presence of strong orientation selectivity in armadillos suggests that the circuitry responsible for this computation is common to all placental mammals.NEW & NOTEWORTHY The current study shows that armadillo primary visual cortex (V1) neurons share the signature properties of V1 neurons of primates, carnivorans, and rodents. Furthermore, these neurons exhibit a degree of selectivity for stimulus orientation and motion direction similar to that found in primate V1. Our findings in armadillo visual cortex suggest that the functional properties of V1 neurons emerged early in the mammalian lineage, near the time of the divergence of marsupials.
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Beaver, Chris J., Quentin S. Fischer, Qinghua Ji, and Nigel W. Daw. "Orientation Selectivity Is Reduced by Monocular Deprivation in Combination With PKA Inhibitors." Journal of Neurophysiology 88, no. 4 (October 1, 2002): 1933–40. http://dx.doi.org/10.1152/jn.2002.88.4.1933.
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We have previously shown that the protein kinase A (PKA) inhibitor, 8-chloroadenosine-3′,5′–monophosphorothioate (Rp-8-Cl-cAMPS), abolishes ocular dominance plasticity in the cat visual cortex. Here we investigate the effect of this inhibitor on orientation selectivity. The inhibitor reduces orientation selectivity in monocularly deprived animals but not in normal animals. In other words, PKA inhibitors by themselves do not affect orientation selectivity, nor does monocular deprivation by itself, but monocular deprivation in combination with a PKA inhibitor does affect orientation selectivity. This result is found for the receptive fields in both deprived and nondeprived eyes. Although there is a tendency for the orientation selectivity in the nondeprived eye to be higher than the orientation selectivity in the deprived eye, the orientation selectivity in both eyes is considerably less than normal. The result is striking in animals at 4 wk of age. The effect of the monocular deprivation on orientation selectivity is reduced at 6 wk of age and absent at 9 wk of age, while the effect on ocular dominance shifts is less changed in agreement with previous results showing that the critical period for orientation/direction selectivity ends earlier than the critical period for ocular dominance. We conclude that closure of one eye in combination with inhibition of PKA reduces orientation selectivity during the period that orientation selectivity is still mutable and that the reduction in orientation selectivity is transferred to the nondeprived eye.
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Humphrey, Allen L., and Alan B. Saul. "Strobe Rearing Reduces Direction Selectivity in Area 17 by Altering Spatiotemporal Receptive-Field Structure." Journal of Neurophysiology 80, no. 6 (December 1, 1998): 2991–3004. http://dx.doi.org/10.1152/jn.1998.80.6.2991.
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Humphrey, Allen L. and Alan B. Saul. Strobe rearing reduces direction selectivity in area 17 by altering spatiotemporal receptive-field structure. J. Neurophysiol. 80: 2991–3004, 1998. Direction selectivity in simple cells of cat area 17 is linked to spatiotemporal (S-T) receptive-field structure. S-T inseparable receptive fields display gradients of response timing across the receptive field that confer a preferred direction of motion. Receptive fields that are not direction selective lack gradients; they are S-T separable, displaying uniform timing across the field. Here we further examine this link using a developmental paradigm that disrupts direction selectivity. Cats were reared from birth to 8 mo of age in 8-Hz stroboscopic illumination. Direction selectivity in simple cells was then measured using gratings drifting at different temporal frequencies (0.25–16 Hz). S-T structure was assessed using stationary bars presented at different receptive-field positions, with bar luminance being modulated sinusoidally at different temporal frequencies. For each cell, plots of response phase versus bar position were fit by lines to characterize S-T inseparability at each temporal frequency. Strobe rearing produced a profound loss of direction selectivity at all temporal frequencies; only 10% of cells were selective compared with 80% in normal cats. The few remaining directional cells were selective over a narrower than normal range of temporal frequencies and exhibited weaker than normal direction selectivity. Importantly, the directional loss was accompanied by a virtual elimination of S-T inseparability. Nearly all cells were S-T separable, like nondirectional cells in normal cats. The loss was clearest in layer 4. Normally, inseparability is greatest there, and it correlates well ( r = 0.77) with direction selectivity; strobe rearing reduced inseparability and direction selectivity to very low values. The few remaining directional cells were inseparable. In layer 6 of normal cats, most direction-selective cells are only weakly inseparable, and there is no consistent relationship between the two measures. However, after strobe rearing, even the weak inseparability was eliminated along with direction selectivity. The correlated changes in S-T structure and direction selectivity were confirmed using conventional linear predictions of directional tuning based on responses to counterphasing bars and white noise stimuli. The developmental changes were permanent, being observed up to 12 yr after strobe rearing. The deficits were remarkably specific; strobe rearing did not affect spatial receptive-field structure, orientation selectivity, spatial or temporal frequency tuning, or general responsiveness to visual stimuli. These results provide further support for a critical role of S-T structure in determining direction selectivity in simple cells. Strobe rearing eliminates directional tuning by altering the timing of responses within the receptive field.
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Livingstone, Margaret S., and Bevil R. Conway. "Substructure of Direction-Selective Receptive Fields in Macaque V1." Journal of Neurophysiology 89, no. 5 (May 1, 2003): 2743–59. http://dx.doi.org/10.1152/jn.00822.2002.
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We used two-dimensional (2-D) sparse noise to map simultaneous and sequential two-spot interactions in simple and complex direction-selective cells in macaque V1. Sequential-interaction maps for both simple and complex cells showed preferred-direction facilitation and null-direction suppression for same-contrast stimulus sequences and the reverse for inverting-contrast sequences, although the magnitudes of the interactions were weaker for the simple cells. Contrast-sign selectivity in complex cells indicates that direction-selective interactions in these cells must occur in antecedent simple cells or in simple-cell-like dendritic compartments. Our maps suggest that direction selectivity, and on andoff segregation perpendicular to the orientation axis, can occur prior to receptive-field elongation along the orientation axis. 2-D interaction maps for some complex cells showed elongated alternating facilitatory and suppressive interactions as predicted if their inputs were orientation-selective simple cells. The negative interactions, however, were less elongated than the positive interactions, and there was an inflection at the origin in the positive interactions, so the interactions were chevron-shaped rather than band-like. Other complex cells showed only two round interaction regions, one negative and one positive. Several explanations for the map shapes are considered, including the possibility that directional interactions are generated directly from unoriented inputs.
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Reid, R. C., R. E. Soodak, and R. M. Shapley. "Directional selectivity and spatiotemporal structure of receptive fields of simple cells in cat striate cortex." Journal of Neurophysiology 66, no. 2 (August 1, 1991): 505–29. http://dx.doi.org/10.1152/jn.1991.66.2.505.
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1. Simple cells in cat striate cortex were studied with a number of stimulation paradigms to explore the extent to which linear mechanisms determine direction selectivity. For each paradigm, our aim was to predict the selectivity for the direction of moving stimuli given only the responses to stationary stimuli. We have found that the prediction robustly determines the direction and magnitude of the preferred response but overestimates the nonpreferred response. 2. The main paradigm consisted of comparing the responses of simple cells to contrast reversal sinusoidal gratings with their responses to drifting gratings (of the same orientation, contrast, and spatial and temporal frequencies) in both directions of motion. Although it is known that simple cells display spatiotemporally inseparable responses to contrast reversal gratings, this spatiotemporal inseparability is demonstrated here to predict a certain amount of direction selectivity under the assumption that simple cells sum their inputs linearly. 3. The linear prediction of the directional index (DI), a quantitative measure of the degree of direction selectivity, was compared with the measured DI obtained from the responses to drifting gratings. The median value of the ratio of the two was 0.30, indicating that there is a significant nonlinear component to direction selectivity. 4. The absolute magnitudes of the responses to gratings moving in both directions of motion were compared with the linear predictions as well. Whereas the preferred direction response showed only a slight amount of facilitation compared with the linear prediction, there was a significant amount of nonlinear suppression in the nonpreferred direction. 5. Spatiotemporal inseparability was demonstrated also with stationary temporally modulated bars. The time course of response to these bars was different for different positions in the receptive field. The degree of spatiotemporal inseparability measured with sinusoidally modulated bars agreed quantitatively with that measured in experiments with stationary gratings. 6. A linear prediction of the responses to drifting luminance borders was compared with the actual responses. As with the grating experiments, the prediction was qualitatively accurate, giving the correct preferred direction but underestimating the magnitude of direction selectivity observed.(ABSTRACT TRUNCATED AT 400 WORDS)
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McClure, John P., and Pierre-Olivier Polack. "Pure tones modulate the representation of orientation and direction in the primary visual cortex." Journal of Neurophysiology 121, no. 6 (June 1, 2019): 2202–14. http://dx.doi.org/10.1152/jn.00069.2019.
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Multimodal sensory integration facilitates the generation of a unified and coherent perception of the environment. It is now well established that unimodal sensory perceptions, such as vision, are improved in multisensory contexts. Whereas multimodal integration is primarily performed by dedicated multisensory brain regions such as the association cortices or the superior colliculus, recent studies have shown that multisensory interactions also occur in primary sensory cortices. In particular, sounds were shown to modulate the responses of neurons located in layers 2/3 (L2/3) of the mouse primary visual cortex (V1). Yet, the net effect of sound modulation at the V1 population level remained unclear. In the present study, we performed two-photon calcium imaging in awake mice to compare the representation of the orientation and the direction of drifting gratings by V1 L2/3 neurons in unimodal (visual only) or multimodal (audiovisual) conditions. We found that sound modulation depended on the tuning properties (orientation and direction selectivity) and response amplitudes of V1 L2/3 neurons. Sounds potentiated the responses of neurons that were highly tuned to the cue’s orientation and direction but weakly active in the unimodal context, following the principle of inverse effectiveness of multimodal integration. Moreover, sound suppressed the responses of neurons untuned for the orientation and/or the direction of the visual cue. Altogether, sound modulation improved the representation of the orientation and direction of the visual stimulus in V1 L2/3. Namely, visual stimuli presented with auditory stimuli recruited a neuronal population better tuned to the visual stimulus orientation and direction than when presented alone. NEW & NOTEWORTHY The primary visual cortex (V1) receives direct inputs from the primary auditory cortex. Yet, the impact of sounds on visual processing in V1 remains controverted. We show that the modulation by pure tones of V1 visual responses depends on the orientation selectivity, direction selectivity, and response amplitudes of V1 neurons. Hence, audiovisual stimuli recruit a population of V1 neurons better tuned to the orientation and direction of the visual stimulus than unimodal visual stimuli.
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Monier, Cyril, Frédéric Chavane, Pierre Baudot, Lyle J. Graham, and Yves Frégnac. "Orientation and Direction Selectivity of Synaptic Inputs in Visual Cortical Neurons." Neuron 37, no. 4 (February 2003): 663–80. http://dx.doi.org/10.1016/s0896-6273(03)00064-3.
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Swindale, NV, JA Matsubara, and MS Cynader. "Surface organization of orientation and direction selectivity in cat area 18." Journal of Neuroscience 7, no. 5 (May 1, 1987): 1414–27. http://dx.doi.org/10.1523/jneurosci.07-05-01414.1987.
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Hei (黑晓娟), Xiaojuan, Carl R. Stoelzel, Jun Zhuang (庄骏), Yulia Bereshpolova, Joseph M. Huff, Jose-Manuel Alonso, and Harvey A. Swadlow. "Directional selective neurons in the awake LGN: response properties and modulation by brain state." Journal of Neurophysiology 112, no. 2 (July 15, 2014): 362–73. http://dx.doi.org/10.1152/jn.00121.2014.
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Directionally selective (DS) neurons are found in the retina and lateral geniculate nucleus (LGN) of rabbits and rodents, and in rabbits, LGN DS cells project to primary visual cortex. Here, we compare visual response properties of LGN DS neurons with those of layer 4 simple cells, most of which show strong direction/orientation selectivity. These populations differed dramatically, suggesting that DS cells may not contribute significantly to the synthesis of simple receptive fields: 1) whereas the first harmonic component (F1)-to-mean firing rate (F0) ratios of LGN DS cells are strongly nonlinear, those of simple cells are strongly linear; 2) whereas LGN DS cells have overlapped ON/OFF subfields, simple cells have either a single ON or OFF subfield or two spatially separate subfields; and 3) whereas the preferred directions of LGN DS cells are closely tied to the four cardinal directions, the directional preferences of simple cells are more evenly distributed. We further show that directional selectivity in LGN DS neurons is strongly enhanced by alertness via two mechanisms, 1) an increase in responses to stimulation in the preferred direction, and 2) an enhanced suppression of responses to stimuli moving in the null direction. Finally, our simulations show that these two consequences of alertness could each serve, in a vector-based population code, to hasten the computation of stimulus direction when rabbits become alert.
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Grigonis, Antony M., Gloria J. Zingaro, and E. Hazel Murphy. "The development of orientation and direction selectivity in the rabbit visual cortex." Developmental Brain Research 40, no. 2 (May 1988): 315–18. http://dx.doi.org/10.1016/0165-3806(88)90145-9.
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Page, William K., Nobuya Sato, Michael T. Froehler, William Vaughn, and Charles J. Duffy. "Navigational path integration by cortical neurons: origins in higher-order direction selectivity." Journal of Neurophysiology 113, no. 6 (March 15, 2015): 1896–906. http://dx.doi.org/10.1152/jn.00197.2014.
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Navigation relies on the neural processing of sensory cues about observer self-movement and spatial location. Neurons in macaque dorsal medial superior temporal cortex (MSTd) respond to visual and vestibular self-movement cues, potentially contributing to navigation and orientation. We moved monkeys on circular paths around a room while recording the activity of MSTd neurons. MSTd neurons show a variety of sensitivities to the monkey's heading direction, circular path through the room, and place in the room. Changing visual cues alters the relative prevalence of those response properties. Disrupting the continuity of self-movement paths through the environment disrupts path selectivity in a manner linked to the time course of single neuron responses. We hypothesize that sensory cues interact with the spatial and temporal integrative properties of MSTd neurons to derive path selectivity for navigational path integration supporting spatial orientation.
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Sakai, Ko, and Haruka Nishimura. "Surrounding Suppression and Facilitation in the Determination of Border Ownership." Journal of Cognitive Neuroscience 18, no. 4 (April 1, 2006): 562–79. http://dx.doi.org/10.1162/jocn.2006.18.4.562.
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Contextual modulation reported in early- to intermediate-level visual areas could be an essential component to signal border ownership (BO) that specifies the direction of figure along a contour. The surrounding regions that evoke significant suppression or facilitation are highly localized and asymmetric with respect to the center of the classical receptive field (CRF). We propose a hypothesis that such surrounding modulation is a basis for BO-selectivity. Although this idea has been discussed for several years, it is uncertain how many of a vast variety of surrounding organizations could signal correctly the direction of ownership, and how many could signal consistently for various stimuli. We carried out computationally a population study of the surrounding effects to investigate how many cells exhibit effective and consistent BO signals. We tested hundreds of various organizations, and found that most of the asymmetric, iso-orientation suppressive regions, regardless of position or size, lead to surprisingly high consistency in the direction of ownership for various stimuli. The combinations of iso-orientation suppression and cross-orientation facilitation indicate both high robustness and consistency in the ownership determination. We constructed a model for BO-selective neurons based on the surrounding effects, and investigated whether the model reproduces major characteristics of the neuronal responses, including a variety in the BO selectivity among neurons, consistency with respect to various stimuli, invariance to stimulus size, and co-selectivity to BO and contrast. The model reproduced successfully the major characteristics of BO-selective neurons.
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Rao, Rajesh P. N. "Bayesian Computation in Recurrent Neural Circuits." Neural Computation 16, no. 1 (January 1, 2004): 1–38. http://dx.doi.org/10.1162/08997660460733976.
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A large number of human psychophysical results have been successfully explained in recent years using Bayesian models. However, the neural implementation of such models remains largely unclear. In this article, we show that a network architecture commonly used to model the cerebral cortex can implement Bayesian inference for an arbitrary hidden Markov model. We illustrate the approach using an orientation discrimination task and a visual motion detection task. In the case of orientation discrimination, we show that the model network can infer the posterior distribution over orientations and correctly estimate stimulus orientation in the presence of significant noise. In the case of motion detection, we show that the resulting model network exhibits direction selectivity and correctly computes the posterior probabilities over motion direction and position. When used to solve the well-known random dots motion discrimination task, the model generates responses that mimic the activities of evidence-accumulating neurons in cortical areas LIP and FEF. The framework we introduce posits a new interpretation of cortical activities in terms of log posterior probabilities of stimuli occurring in the natural world.
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Berberian, Nareg, Matt Ross, and Sylvain Chartier. "Discrimination of Motion Direction in a Robot Using a Phenomenological Model of Synaptic Plasticity." Computational Intelligence and Neuroscience 2019 (May 2, 2019): 1–14. http://dx.doi.org/10.1155/2019/6989128.
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Recognizing and tracking the direction of moving stimuli is crucial to the control of much animal behaviour. In this study, we examine whether a bio-inspired model of synaptic plasticity implemented in a robotic agent may allow the discrimination of motion direction of real-world stimuli. Starting with a well-established model of short-term synaptic plasticity (STP), we develop a microcircuit motif of spiking neurons capable of exhibiting preferential and nonpreferential responses to changes in the direction of an orientation stimulus in motion. While the robotic agent processes sensory inputs, the STP mechanism introduces direction-dependent changes in the synaptic connections of the microcircuit, resulting in a population of units that exhibit a typical cortical response property observed in primary visual cortex (V1), namely, direction selectivity. Visually evoked responses from the model are then compared to those observed in multielectrode recordings from V1 in anesthetized macaque monkeys, while sinusoidal gratings are displayed on a screen. Overall, the model highlights the role of STP as a complementary mechanism in explaining the direction selectivity and applies these insights in a physical robot as a method for validating important response characteristics observed in experimental data from V1, namely, direction selectivity.
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Ziskind, Avi J., Al A. Emondi, Andrei V. Kurgansky, Sergei P. Rebrik, and Kenneth D. Miller. "Neurons in cat V1 show significant clustering by degree of tuning." Journal of Neurophysiology 113, no. 7 (April 2015): 2555–81. http://dx.doi.org/10.1152/jn.00646.2014.
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Neighboring neurons in cat primary visual cortex (V1) have similar preferred orientation, direction, and spatial frequency. How diverse is their degree of tuning for these properties? To address this, we used single-tetrode recordings to simultaneously isolate multiple cells at single recording sites and record their responses to flashed and drifting gratings of multiple orientations, spatial frequencies, and, for drifting gratings, directions. Orientation tuning width, spatial frequency tuning width, and direction selectivity index (DSI) all showed significant clustering: pairs of neurons recorded at a single site were significantly more similar in each of these properties than pairs of neurons from different recording sites. The strength of the clustering was generally modest. The percent decrease in the median difference between pairs from the same site, relative to pairs from different sites, was as follows: for different measures of orientation tuning width, 29–35% (drifting gratings) or 15–25% (flashed gratings); for DSI, 24%; and for spatial frequency tuning width measured in octaves, 8% (drifting gratings). The clusterings of all of these measures were much weaker than for preferred orientation (68% decrease) but comparable to that seen for preferred spatial frequency in response to drifting gratings (26%). For the above properties, little difference in clustering was seen between simple and complex cells. In studies of spatial frequency tuning to flashed gratings, strong clustering was seen among simple-cell pairs for tuning width (70% decrease) and preferred frequency (71% decrease), whereas no clustering was seen for simple-complex or complex-complex cell pairs.
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Schwark, H. D., J. G. Malpeli, T. G. Weyand, and C. Lee. "Cat area 17. II. Response properties of infragranular layer neurons in the absence of supragranular layer activity." Journal of Neurophysiology 56, no. 4 (October 1, 1986): 1074–87. http://dx.doi.org/10.1152/jn.1986.56.4.1074.
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Response properties of cells in the infragranular layers of cortical area 17 of the cat were examined in the absence of input from supragranular layers. Supragranular activity was silenced either reversibly by cooling the surface of cortex or permanently by making a cryogenic lesion of the supragranular layers. Visually driven responses of cells throughout the cortical column were recorded with a linear array of electrodes. Most infragranular layer cells continued to be visually responsive in the absence of supragranular layer input. These cells were similar to normal infragranular layer cells on measures of visual responsiveness, orientation selectivity, and direction selectivity. Special complex, but not standard complex, cells were absent in layer 5 when supragranular layers were destroyed. We found no evidence for a selective effect of removal of supragranular activity on the response properties of cells in layer 6. We propose that the intracolumnar projection from the supragranular layers drives the special complex cells of layer 5, but is not necessary for the visual driving of most other infragranular layer cells. This projection does not impose selectivity for stimulus orientation or direction on the remaining active cells of the infragranular layers.
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BAKER, CURTIS L. "Linear filtering and nonlinear interactions in direction-selective visual cortex neurons: A noise correlation analysis." Visual Neuroscience 18, no. 3 (May 2001): 465–85. http://dx.doi.org/10.1017/s0952523801183136.
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Spatial and temporal properties related to direction selectivity of both simple and complex type visual cortex neurons were assessed by cross-correlation analysis of their responses to random ternary white noise. This stimulus consisted of multiple randomly placed bars, each colored white, black, or gray with equal probability, which were rerandomized every 5–10 ms. A first-order cross-correlation analysis of a neuron's spike train with the spatiotemporal history of the stimulus provided an estimate of the neuron's linear spatiotemporal filtering properties. A nonlinear correlation analysis measured the amount of interaction for pair-wise combinations of bars as a function of their relative spatial and temporal separations. The spatiotemporal orientation of each of these functions was quantified using a “motion energy index” (MEI), which was compared to the neurons' direction selectivity measured with drifting sinewave gratings. Both first-order and nonlinear correlation plots usually showed s–t orientation whose sign was consistent with the neuron's direction preference; however, in many cases the MEI for first-order analysis was weak compared to that seen in the nonlinear interactions. The structures of the nonlinear interaction functions were also compared with predictions from a conventional model of direction selectivity based on a simple spatiotemporally oriented linear filter, followed by an intensive nonlinearity (“LN model”). These comparisons showed that some neurons' data agreed reasonably well with such a model, while others agreed poorly or not at all. Simulations of an alternative model which combines signals from idealized lagged and nonlagged front-end linear filters produce noise correlation results more like those seen in the neurophysiological data.
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Albrecht, Duane G., and Wilson S. Geisler. "Motion selectivity and the contrast-response function of simple cells in the visual cortex." Visual Neuroscience 7, no. 6 (December 1991): 531–46. http://dx.doi.org/10.1017/s0952523800010336.
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AbstractThe responses of simple cells were recorded from the visual cortex of cats, as a function of the position and contrast of counterphase and drifting grating patterns, to assess whether direction selectivity can be accounted for on the basis of linear summation. The expected responses to a counterphase grating, given a strictly linear model, would be the sum of the responses to the two drifting components. The measured responses were not consistent with the linear prediction. For example, nearly all cells showed two positions where the responses approached zero (i.e. two “null phase positions”); this was true, even for the most direction selective cells. However, the measured responses were consistent with the hypothesis that direction selectivity is a consequence of the linear spatiotemporal receptive-field structure, coupled with the nonlinearities revealed by the contrast-response function: contrast gain control, halfwave rectification, and expansive exponent. When arranged in a particular sequence, each of these linear and nonlinear mechanisms performs a useful function in a general model of simple cells. The linear spatiotemporal receptive field initiates stimulus selectivity (for direction, orientation, spatial frequency, etc.). The expansive response exponent enhances selectivity. The contrast-set gain control maintains selectivity (over a wide range of contrasts, in spite of the limited dynamic response range and steep slope of the contrast-response function). Rectification conserves metabolic energy.
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Michalski, A., B. M. Wimborne, and G. H. Henry. "The role of ipsilateral and contralateral inputs from primary cortex in responses of area 21a neurons in cats." Visual Neuroscience 11, no. 5 (September 1994): 839–49. http://dx.doi.org/10.1017/s0952523800003801.
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AbstractNeuronal responses in cat visual area 21a were analyzed when the primary visual cortex (areas 17 and 18) was deactivated by cooling. Ipsilateral and contralateral cortices were deactivated separately. Results established that (1) cooling the ipsilateral primary cortex diminished the activity of all area 21a cells and, in 30%, blocked responsiveness altogether, and (2) cooling the contralateral primary cortex initially increased activity in area 21a cells but, with further cooling, reduced it to below the original level although only 9% of cells ceased responding. These findings were then compared to earlier results in which bilateral deactivation of the primary cortex greatly reduced and, in most cases, blocked the activity of area 21a cells (Michalski et al., 1993). Despite the response attenuation following cooling of the primary visual cortex (either ipsilateral or contralateral), neurons of area 21a retained their original orientation specificity and sharpness of tuning (measured as the half-width at half-height of the orientation tuning curve). Direction selectivity also tended to remain unchanged. We concluded that for area 21a cells (1) the ipsilateral primary cortex provides the main excitatory input; (2) the contralateral primary cortex supplies a large inhibitory input; and (3) the nature of orientation specificity, sharpness of orientation tuning, and direction selectivity are largely unaffected by removal of the ipsilateral hemisphere excitatory input or the contralateral hemisphere inhibitory input.
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Scholl, Benjamin, Jagruti J. Pattadkal, Ashlee Rowe, and Nicholas J. Priebe. "Functional characterization and spatial clustering of visual cortical neurons in the predatory grasshopper mouse Onychomys arenicola." Journal of Neurophysiology 117, no. 3 (March 1, 2017): 910–18. http://dx.doi.org/10.1152/jn.00779.2016.
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Mammalian neocortical circuits are functionally organized such that the selectivity of individual neurons systematically shifts across the cortical surface, forming a continuous map. Maps of the sensory space exist in cortex, such as retinotopic maps in the visual system or tonotopic maps in the auditory system, but other functional response properties also may be similarly organized. For example, many carnivores and primates possess a map for orientation selectivity in primary visual cortex (V1), whereas mice, rabbits, and the gray squirrel lack orientation maps. In this report we show that a carnivorous rodent with predatory behaviors, the grasshopper mouse ( Onychomys arenicola), lacks a canonical columnar organization of orientation preference in V1; however, neighboring neurons within 50 μm exhibit related tuning preference. Using a combination of two-photon microscopy and extracellular electrophysiology, we demonstrate that the functional organization of visual cortical neurons in the grasshopper mouse is largely the same as in the C57/BL6 laboratory mouse. We also find similarity in the selectivity for stimulus orientation, direction, and spatial frequency. Our results suggest that the properties of V1 neurons across rodent species are largely conserved. NEW & NOTEWORTHY Carnivores and primates possess a map for orientation selectivity in primary visual cortex (V1), whereas rodents and lagomorphs lack this organization. We examine, for the first time, V1 of a wild carnivorous rodent with predatory behaviors, the grasshopper mouse ( Onychomys arenicola). We demonstrate the cellular organization of V1 in the grasshopper mouse is largely the same as the C57/BL6 laboratory mouse, suggesting that V1 neuron properties across rodent species are largely conserved.
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Jansen-Amorim, A. K., M. Fiorani, and R. Gattass. "GABA-induced inactivation of Cebus apella V2 neurons: effects on orientation tuning and direction selectivity." Brazilian Journal of Medical and Biological Research 46, no. 7 (July 2013): 589–600. http://dx.doi.org/10.1590/1414-431x20132859.
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Moore, B. D., H. J. Alitto, and W. M. Usrey. "The influence of stimulus temporal frequency on orientation tuning and direction selectivity in V1 neurons." Journal of Vision 4, no. 8 (August 1, 2004): 274. http://dx.doi.org/10.1167/4.8.274.
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Hunter, P. R., A. S. Lowe, I. D. Thompson, and M. P. Meyer. "Emergent Properties of the Optic Tectum Revealed by Population Analysis of Direction and Orientation Selectivity." Journal of Neuroscience 33, no. 35 (August 28, 2013): 13940–45. http://dx.doi.org/10.1523/jneurosci.1493-13.2013.
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Marcar, V. L., D. K. Xiao, S. E. Raiguel, H. Maes, and G. A. Orban. "Processing of kinetically defined boundaries in the cortical motion area MT of the macaque monkey." Journal of Neurophysiology 74, no. 3 (September 1, 1995): 1258–70. http://dx.doi.org/10.1152/jn.1995.74.3.1258.
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1. Electrophysiological recordings of 68 cells in the middle temporal area MT were made in paralyzed and anesthetized macaque monkeys. 2. Testing with our kinetic boundary stimuli always occurred under optimized conditions. To this end, the preferred direction, speed, stimulus position, and stimulus size of each cell were determined by quantitative tests. 3. The orientation selectivity to stationary luminance contrast edges served as a reference by which a response to kinetic boundaries could be compared. We found cells in area MT to be less selective to the orientation of luminance contrast stimuli than to the direction of motion. We confirmed the presence of neurons with preferred orientation aligned with their preferred direction. 4. The responses to kinetic edges defined by motion vectors moving in opposite directions, kinetic gratings with motion vectors in opposite directions, kinetic edges containing coherent motion and a stationary complementary field or coherent motion and a complementary field containing visual dynamic noise were compared. Kinetic boundaries were generated so that the motion vectors moved either parallel or orthogonal to the orientation of the discontinuity. For a cell to be considered as responding to the orientation of a kinetic boundary, it had to exhibit the same preferred orientation when the local motion vectors changed from parallel to orthogonal to the orientation of the kinetic boundary. 5. All cells in area MT changed their preferred orientation by 90 degrees when the coherent motion vectors changed from moving parallel to moving orthogonal to the boundary. This was the case independent of the types of kinetic boundary tested. We concluded that cells in area MT appear to respond to the motion vector over their classical receptive field (CRF) only and were unable to code the orientation of the kinetic boundary. 6. In those cells exhibiting an antagonistic surround, we examined the ability of the cell to code the position of a kinetic boundary. None of the cells tested signaled the position of a kinetic boundary. The side preference of the stimulus of the cells changed from left to right as the motion vectors in the stimulus reversed. This indicates that the cells were only selective for the motion vectors present over their CRF. 7. We found that the directional sensitivity of cells in area MT remained unaltered by the presence of additional motion vectors within the CRF. This suggests that cells in area MT extract a specific motion vector from a spatial configuration of vectors.(ABSTRACT TRUNCATED AT 400 WORDS)
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Larsson, Jonas, David J. Heeger, and Michael S. Landy. "Orientation Selectivity of Motion-Boundary Responses in Human Visual Cortex." Journal of Neurophysiology 104, no. 6 (December 2010): 2940–50. http://dx.doi.org/10.1152/jn.00400.2010.
Full textAbstract:
Motion boundaries (local changes in visual motion direction) arise naturally when objects move relative to an observer. In human visual cortex, neuroimaging studies have identified a region (the kinetic occipital area [KO]) that responds more strongly to motion-boundary stimuli than to transparent-motion stimuli. However, some functional magnetic resonance imaging (fMRI) studies suggest that KO may encompass multiple visual areas and single-unit studies in macaque visual cortex have identified neurons selective for motion-boundary orientation in areas V2, V3, and V4, implying that motion-boundary selectivity may not be restricted to a single area. It is not known whether fMRI responses to motion boundaries are selective for motion-boundary orientation, as would be expected if these responses reflected the population activity of motion-boundary–selective neurons. We used an event-related fMRI adaptation protocol to measure orientation-selective responses to motion boundaries in human visual cortex. On each trial, we measured the response to a probe stimulus presented after an adapter stimulus (a vertical or horizontal motion-boundary grating). The probe stimulus was either a motion-boundary grating oriented parallel or orthogonal to the adapter stimulus or a transparent-motion stimulus. Orientation-selective adaptation for motion boundaries—smaller responses for trials in which test and adapter stimuli were parallel to each other—was observed in multiple extrastriate visual areas. The strongest adaptation, relative to the unadapted responses, was found in V3A, V3B, LO1, LO2, and V7. Most of the visual areas that exhibited orientation-selective adaptation in our data also showed response preference for motion boundaries over transparent motion, indicating that most of the human visual areas previously shown to respond to motion boundaries are also selective for motion-boundary orientation. These results suggest that neurons selective for motion-boundary orientation are distributed across multiple human visual cortical areas and argue against the existence of a single region or area specialized for motion-boundary processing.
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Brunken, William J., and Nigel W. Daw. "The effects of serotonin agonists and antagonists on the response properties of complex ganglion cells in the rabbit's retina." Visual Neuroscience 1, no. 2 (March 1988): 181–88. http://dx.doi.org/10.1017/s0952523800001450.
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AbstractSelective agonists and antagonists were employed to determine the role of indoleaminergic amacrine cells in the generation of the light-evoked responses and spontaneous activity of direction and orientation selective cells. Perfusion with 5-HT2 antagonists reduced the spontaneous activity and both the leading and trailing edge responses of ON/OFF direction selective cells. 5-HT1a agonists had a similar effect on this class of cell, namely, a reduction of light-evoked and spontaneous activity. Results from ON-center and OFF-center orientation selective cells were consistent with those obtained from direction selective cells in that no disruption of direction or orientation selectivity was observed during perfusion of these drugs. These data suggest that the indoleaminergic cells are not directly involved in the generation of the trigger features of complex ganglion cells, but may be facilitating synaptic transmission in the inner retina. This function is discussed relative to the connectivity of the rod bipolar cells and the putative indoleaminergic amacrine cells. The similarity of the effects of 5-HT1a agonists and 5-HT2 antagonists supports the hypothesis, developed during our prior studies of brisk ganglion cells, that these two receptor classes mediate antagonistic processes in the target neurons.
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Dreher, B., A. Michalski, B. G. Cleland, and W. Burke. "Effects of selective pressure block of Y-type optic nerve fibers on the receptive-field properties of neurons in area 18 of the visual cortex of the cat." Visual Neuroscience 9, no. 1 (July 1992): 65–78. http://dx.doi.org/10.1017/s0952523800006374.
Full textAbstract:
AbstractRecordings were made from single neurons in area 18 of anesthetized cats (N2O/O2 mixture supplemented by continuous intravenous infusion of barbiturate) in which one optic nerve had been pressure blocked to selectively block conduction in the largest (Y-type) fibers. Cortical neurons were stimulated visually via the normal eye or via the eye with the pressure-blocked optic nerve (“Y-blocked eye”). Several properties of the receptive fields such as their spatial organization (S or C cells), orientation tuning, and the presence and strength of end-zone inhibition appear to be unaffected by removal of the Y input. By contrast, the removal of the Y input resulted in a small but significant reduction in the size of the discharge field and in the direction-selectivity index. In three respects, peak response discharge rate, eye dominance, and velocity sensitivity, removal of the Y input had strong and highly significant effects. Thus, the mean peak discharge frequency of responses evoked by the stimulation of binocular neurons via the Y-blocked eye was significantly lower than that of responses evoked by the stimulation via the normal eye. Accordingly, the eye-dominance histogram was shifted markedly towards the normal eye (more so than in the homologous experiment conducted on area 17 — Burke et al., 1992). Finally, the mean preferred velocity of responses of cells activated via the normal eye was in the vicinity of 145 deg/s, whereas for cells activated via the Y-blocked eye the value was about 35 deg/s. Overall, the results of the present study imply that (1) apart from Y-type excitatory input there are significant excitatory non-Y-inputs to area 18; these inputs at least partially consist of indirect X-type input relayed via area 17; (2) in neurons of area 18 that receive both Y-type and non-Y-type excitatory inputs, the Y-type input has a major influence on strength of the response and velocity sensitivity and a lesser influence on the direction selectivity and size of the discharge fields; and (3) area 18 contains mechanisms determining such receptive-field properties as S- or C-type organization, orientation tuning, and direction selectivity which can be accessed either by the Y input or by non-Y input.
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Swindale, N. V. "The Spatial Pattern of Response Magnitude and Selectivity for Orientation and Direction in Cat Visual Cortex." Cerebral Cortex 13, no. 3 (March 1, 2003): 225–38. http://dx.doi.org/10.1093/cercor/13.3.225.
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Gur, Moshe, Igor Kagan, and D. Max Snodderly. "Orientation and Direction Selectivity of Neurons in V1 of Alert Monkeys: Functional Relationships and Laminar Distributions." Cerebral Cortex 15, no. 8 (December 22, 2004): 1207–21. http://dx.doi.org/10.1093/cercor/bhi003.
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Sernagor, E., and N. M. Grzywacz. "Emergence of complex receptive field properties of ganglion cells in the developing turtle retina." Journal of Neurophysiology 73, no. 4 (April 1, 1995): 1355–64. http://dx.doi.org/10.1152/jn.1995.73.4.1355.
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1. Receptive field properties of adult retinal ganglion cells are well documented, but little is known about their development. We made extracellular recordings of activity from turtle retinal ganglion cells during embryogenesis (stages 22-26), during the first 40 days posthatching, and in adults. 2. From stage 22 the cells fired in spontaneous recurring bursts, and from stage 23 they responded to light. Polar plots of the responses to motion were highly anisotropic in early embryonic cells. More than 40% of embryonic cells exhibited multiaxis anisotropy, and only 6% were statistically isotropic. The incidence of anisotropic cells gradually decreased throughout development. The incidence of isotropic cells and the excitatory receptive field diameters of all ganglion cells gradually increased during development and their maturation coincided with the disappearance of the spontaneous bursts (2-4 wk posthatching). 3. Both sensitivities to stimulus orientation and direction of motion were observed at the earliest stages of development. However, orientation selectivity reached a peak incidence at hatching, whereas directional selectivity completely disappeared, only to reappear in adults. 4. These results show that mature spatiotemporal receptive field properties of retinal ganglion cells emerge from initially highly anisotropic properties, which may reflect an immature, polarized dendritic layout. Their maturation might be mediated by dendritic outgrowth and strengthening of excitatory synaptic connections, which could be induced by spontaneous activity and driven to maturation by exposure to light at birth. Mature directional selectivity seems to require visual experience or the late establishment of a specialized inhibitory synaptic drive.
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Cavanaugh, James R., Wyeth Bair, and J. Anthony Movshon. "Selectivity and Spatial Distribution of Signals From the Receptive Field Surround in Macaque V1 Neurons." Journal of Neurophysiology 88, no. 5 (November 1, 2002): 2547–56. http://dx.doi.org/10.1152/jn.00693.2001.
Full textAbstract:
The responsiveness of neurons in V1 is modulated by stimuli placed outside their classical receptive fields. This nonclassical surround provides input from a larger portion of the visual scene than originally thought, permitting integration of information at early levels in the visual processing stream. Signals from the surround have been reported variously to be suppressive and facilitatory, selective and unselective. We tested the specificity of influences from the surround by studying the interactions between drifting sinusoidal gratings carefully confined to conservatively defined center and surround regions. We found that the surround influence was always suppressive when the surround grating was at the neuron's preferred orientation. Suppression tended to be stronger when the surround grating also moved in the neuron's preferred direction, rather than its opposite. When the orientation in the surround was 90° from the preferred orientation (orthogonal), suppression was weaker, and facilitation was sometimes evident. The tuning of surround signals therefore tended to match the tuning of the center, though the tuning of the surround was somewhat broader. The tuning of suppression also depended on the contrast of the center grating—when the center grating was reduced in contrast, orthogonal surround stimuli became relatively more suppressive. We also found evidence for the tuning of the surround being dependent to some degree on the stimulus used in the center—suppression was often stronger for a given center stimulus when the parameters of the surround grating matched the parameters of the center grating even when the center grating was not itself of the optimal direction or orientation. We also explored the spatial distribution of surround influence and found an orderly relationship between the orientation of grating patches presented to regions of the surround and the position of greatest suppression. When surround gratings were oriented parallel to the preferred orientation of the receptive field, suppression was strongest at the receptive field ends. When surround gratings were orthogonal, suppression was strongest on the flanks. We conclude that the surround has complex effects on responses from the classical receptive field. We suggest that the underlying mechanism of this complexity may involve interactions between relatively simple center and surround mechanisms.
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Meso, Andrew Isaac, Anna Montagnini, Jason Bell, and Guillaume S. Masson. "Looking for symmetry: fixational eye movements are biased by image mirror symmetry." Journal of Neurophysiology 116, no. 3 (September 1, 2016): 1250–60. http://dx.doi.org/10.1152/jn.01152.2015.
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Humans are highly sensitive to symmetry. During scene exploration, the area of the retina with dense light receptor coverage acquires most information from relevant locations determined by gaze fixation. We characterized patterns of fixational eye movements made by observers staring at synthetic scenes either freely (i.e., free exploration) or during a symmetry orientation discrimination task (i.e., active exploration). Stimuli could be mirror-symmetric or not. Both free and active exploration generated more saccades parallel to the axis of symmetry than along other orientations. Most saccades were small (<2°), leaving the fovea within a 4° radius of fixation. Analysis of saccade dynamics showed that the observed parallel orientation selectivity emerged within 500 ms of stimulus onset and persisted throughout the trials under both viewing conditions. Symmetry strongly distorted existing anisotropies in gaze direction in a seemingly automatic process. We argue that this bias serves a functional role in which adjusted scene sampling enhances and maintains sustained sensitivity to local spatial correlations arising from symmetry.
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Dreher, B., A. Michalski, R. H. T. Ho, C. W. F. Lee, and W. Burke. "Processing of form and motion in area 21a of cat visual cortex." Visual Neuroscience 10, no. 1 (January 1993): 93–115. http://dx.doi.org/10.1017/s0952523800003254.
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AbstractExtracellular recordings from single neurons have been made from presumed area 21a of the cerebral cortex of the cat, anesthetized with N2O/O2/sodium pentobarbitone mixture. Area 21a contains mainly a representation of a central horizontal strip of contralateral visual field about 5 deg above and below the horizontal meridian.Excitatory discharge fields of area 21a neurons were substantially (or slightly but significantly) larger than those of neurons at corresponding eccentricities in areas 17, 19, or 18, respectively. About 95% of area 21a neurons could be activated through either eye and the input from the ipsilateral eye was commonly dominant. Over 90% and less than 10% of neurons had, respectively, C-type and S-type receptive-field organization. Virtually all neurons were orientation-selective and the mean width at half-height of the orientation tuning curves at 52.9 deg was not significantly different from that of neurons in areas 17 and 18. About 30% of area 21a neurons had preferred orientations within 15 deg of the vertical.The mean direction-selectivity index (32.8%) of area 21a neurons was substantially lower than the indices for neurons in areas 17 or 18. Only a few neurons exhibited moderately strong end-zone inhibition. Area 21a neurons responded poorly to fast-moving stimuli and the mean preferred velocity at about 12.5 deg/s was not significantly different from that for area 17 neurons.Selective pressure block of Y fibers in contralateral optic nerve resulted in a small but significant reduction in the preferred velocities of neurons activated via the Y-blocked eye. By contrast, removal of the Y input did not produce significant changes in the spatial organization of receptive fields (S or C type), the size of the discharge fields, the width of orientation tuning curves, or direction-selectivity indices.Our results are consistent with the idea that area 21a receives its principal excitatory input from area 17 and is involved mainly in form rather than motion analysis.
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Sato, H., N. Katsuyama, H. Tamura, Y. Hata, and T. Tsumoto. "Mechanisms underlying direction selectivity of neurons in the primary visual cortex of the macaque." Journal of Neurophysiology 74, no. 4 (October 1, 1995): 1382–94. http://dx.doi.org/10.1152/jn.1995.74.4.1382.
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1. We studied the effects of blocking intracortical inhibition by microiontophoretic administration of bicuculline methiodide (BMI), a selective antagonist for gamma-aminobutyric acid-A receptors, on direction sensitivity of 103 neurons in the primary visual cortex (VI) of anesthetized and paralyzed monkeys. 2. The direction selectivity index (DSI) of each cell was calculated for the control response and response during the BMI administration at the optimal stimulus orientation to assess the directionality of an individual cell. 3. The averaged direction tuning of visual responses of cells was sharp in layers IVa and IVb, moderate in both interblob and blob regions of layer II/III and layers V and VI, and poor in layers IVc alpha and IVc beta. 4. Iontophoretic administration of BMI uncovered or facilitated responses to stimuli moving in the nonpreferred direction, and reduced DSIs of cells to a varying extent in all the layers except layer VI. Responses to stimuli moving in the preferred direction were also facilitated so that a slight bias of response toward the originally preferred direction remained during BMI administration in most cells. 5. Most of the cells in layers II/III (both blobs and interblobs) and IVb that receive inputs from layers IVc alpha and IVc beta showed a clear reduction of direction selectivity during BMI administration. This result suggests that intracortical inhibition plays an important role in the elaboration of direction selectivity at the second stage of information processing in VI. 6. The direction selectivity of cells in layer VI was most resistant to the effects of BMI, suggesting that it is dependent on excitatory inputs that are already direction selective, even though the sample size of this layer was small. 7. In direction-selective cells outside layer VI, responses to a stimulus moving in the preferred direction were enhanced in a way that was linearly related with those in the nonpreferred direction as the BMI dose was increased. This suggests that various amounts of inhibition interact linearly with directionally biased excitatory inputs to raise the firing threshold to various levels so as to produce various degrees of directionality. 8. These results suggest that, in most of the directionally sensitive cells except for those in layer VI, there are excitatory inputs which are bidirectional but slightly biased to one direction, and that the intracortical inhibition raises a threshold level of responses to excitatory inputs so that the response become direction selective.