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Przybyszewski, Andrzej W., Igor Kagan i D. Max Snodderly. "Primate area V1". NeuroReport 25, nr 14 (październik 2014): 1109–15. http://dx.doi.org/10.1097/wnr.0000000000000235.
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Xu, Xiangmin, William H. Bosking, Leonard E. White, David Fitzpatrick i Vivien A. Casagrande. "Functional Organization of Visual Cortex in the Prosimian Bush Baby Revealed by Optical Imaging of Intrinsic Signals". Journal of Neurophysiology 94, nr 4 (październik 2005): 2748–62. http://dx.doi.org/10.1152/jn.00354.2005.
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Cells in primary visual cortex (V1) of primates and carnivores respond most strongly to a visual stimulus presented to one eye, in a particular visual field location, and at a particular orientation. Each of these stimulus attributes is mapped across the cortical surface, and, in macaque monkeys and cats, strong geometrical relationships exist between these feature maps. In macaque V1 and V2, correlations between feature maps and cytochrome oxidase (CO)-rich modules have also been observed. To see if such relationships reflect a conserved principle of V1 functional architecture among primate species, we examined these maps in the prosimian bush baby, a species that has been proposed to represent the ancestral primate organization. We found that the layout of individual feature maps in bush baby V1 is similar to that of other primates, but we found an entirely different organization of orientation preference in bush baby V2 compared with that reported in simian primates. Another striking distinction between bush baby and simian species is that we observed no strong relationships among maps of orientation, ocular dominance, and CO blobs in V1. Thus our findings suggest that precise relationships between feature maps are not a common element of the functional organization in all primates and that such relationships are not necessary for achieving basic coverage of stimulus feature combinations. In addition, our results suggest that specific relationships between feature maps in V1, and the subdivision of V2 into functional compartments, may have arisen comparatively late in the evolution of primates.
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Kaas, Jon H., i Mary K. L. Baldwin. "The Evolution of the Pulvinar Complex in Primates and Its Role in the Dorsal and Ventral Streams of Cortical Processing". Vision 4, nr 1 (30.12.2019): 3. http://dx.doi.org/10.3390/vision4010003.
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Current evidence supports the view that the visual pulvinar of primates consists of at least five nuclei, with two large nuclei, lateral pulvinar ventrolateral (PLvl) and central lateral nucleus of the inferior pulvinar (PIcl), contributing mainly to the ventral stream of cortical processing for perception, and three smaller nuclei, posterior nucleus of the inferior pulvinar (PIp), medial nucleus of the inferior pulvinar (PIm), and central medial nucleus of the inferior pulvinar (PIcm), projecting to dorsal stream visual areas for visually directed actions. In primates, both cortical streams are highly dependent on visual information distributed from primary visual cortex (V1). This area is so vital to vision that patients with V1 lesions are considered “cortically blind”. When the V1 inputs to dorsal stream area middle temporal visual area (MT) are absent, other dorsal stream areas receive visual information relayed from the superior colliculus via PIp and PIcm, thereby preserving some dorsal stream functions, a phenomenon called “blind sight”. Non-primate mammals do not have a dorsal stream area MT with V1 inputs, but superior colliculus inputs to temporal cortex can be more significant and more visual functions are preserved when V1 input is disrupted. The current review will discuss how the different visual streams, especially the dorsal stream, have changed during primate evolution and we propose which features are retained from the common ancestor of primates and their close relatives.
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Jones, H. E., K. L. Grieve, W. Wang i A. M. Sillito. "Surround Suppression in Primate V1". Journal of Neurophysiology 86, nr 4 (1.10.2001): 2011–28. http://dx.doi.org/10.1152/jn.2001.86.4.2011.
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We investigated the spatial organization of surround suppression in primate primary visual cortex (V1). We utilized drifting stimuli, configured to extend either from within the classical receptive field (CRF) to surrounding visual space, or from surrounding visual space into the CRF or subdivided to generate direction contrast, to make a detailed examination of the strength, spatial organization, direction dependence, mechanisms, and laminar distribution of surround suppression. Most cells (99/105, 94%) through all cortical layers, exhibited suppression (mean reduction 67%) to uniform stimuli exceeding the CRF, and 43% exhibited a more than 70% reduction. Testing with an annulus revealed two different patterns of surround influence. Some cells (37% of cells), classical surround suppression (CSS) cells exhibited responses to an annulus encroaching on the CRF that were less than the plateau in the spatial summation curve. The majority (63%), center-gated surround suppression (CGSS) cells, showed responses to annuli that equaled or exceeded the plateau in the spatial summation curve. Analysis suggested the CSS mechanism was implemented in all cells while the CGSS mechanism was implemented in varying strength across the sample with the extreme reflected in cells that gave larger responses to annuli than to a center stimulus. Reversing the direction of motion of the portion of the stimulus surrounding the CRF revealed four different patterns of effect: no reduction in the degree of suppression (22% of cells), a reduction in surround suppression (41%), a facilitation of the response above the level to the inner stimulus alone (37%), and a facilitation of the response above that to the inner stimulus alone that also exceeded the values associated with an optimal inner stimulus. The facilitatory effects were only seen for reverse direction interfaces between the central and surrounding stimulus at diameters equal to or more than the CRF size. The zones driving the suppressive influences and the direction contrast facilitation were often spatially heterogeneous and for a number of cells bore strong comparison with the class of behavior reported for surround mechanisms in MT. This suggests a potential role, for example, in extracting information about motion contrast in the representation of the three dimensional structure of moving objects.
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Song, Byeongwoon, Bert Gold, Colm O'hUigin, Hassan Javanbakht, Xing Li, Matthew Stremlau, Cheryl Winkler, Michael Dean i Joseph Sodroski. "The B30.2(SPRY) Domain of the Retroviral Restriction Factor TRIM5α Exhibits Lineage-Specific Length and Sequence Variation in Primates". Journal of Virology 79, nr 10 (15.05.2005): 6111–21. http://dx.doi.org/10.1128/jvi.79.10.6111-6121.2005.
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ABSTRACT Tripartite motif (TRIM) proteins are composed of RING, B-box 2, and coiled coil domains. Some TRIM proteins, such as TRIM5α, also possess a carboxy-terminal B30.2(SPRY) domain and localize to cytoplasmic bodies. TRIM5α has recently been shown to mediate innate intracellular resistance to retroviruses, an activity dependent on the integrity of the B30.2 domain, in particular primate species. An examination of the sequences of several TRIM proteins related to TRIM5 revealed the existence of four variable regions (v1, v2, v3, and v4) in the B30.2 domain. Species-specific variation in TRIM5α was analyzed by amplifying, cloning, and sequencing nonhuman primate TRIM5 orthologs. Lineage-specific expansion and sequential duplication occurred in the TRIM5α B30.2 v1 region in Old World primates and in v3 in New World monkeys. We observed substitution patterns indicative of selection bordering these particular B30.2 domain variable elements. These results suggest that occasional, complex changes were incorporated into the TRIM5α B30.2 domain at discrete time points during the evolution of primates. Some of these time points correspond to periods during which primates were exposed to retroviral infections, based on the appearance of particular endogenous retroviruses in primate genomes. The results are consistent with a role for TRIM5α in innate immunity against retroviruses.
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Seidemann, Eyal, i Wilson S. Geisler. "Linking V1 Activity to Behavior". Annual Review of Vision Science 4, nr 1 (15.09.2018): 287–310. http://dx.doi.org/10.1146/annurev-vision-102016-061324.
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A long-term goal of visual neuroscience is to develop and test quantitative models that account for the moment-by-moment relationship between neural responses in early visual cortex and human performance in natural visual tasks. This review focuses on efforts to address this goal by measuring and perturbing the activity of primary visual cortex (V1) neurons while nonhuman primates perform demanding, well-controlled visual tasks. We start by describing a conceptual approach—the decoder linking model (DLM) framework—in which candidate decoding models take neural responses as input and generate predicted behavior as output. The ultimate goal in this framework is to find the actual decoder—the model that best predicts behavior from neural responses. We discuss key relevant properties of primate V1 and review current literature from the DLM perspective. We conclude by discussing major technological and theoretical advances that are likely to accelerate our understanding of the link between V1 activity and behavior.
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Rosa, Marcello G. P., Vivien A. Casagrande, Todd Preuss i Jon H. Kaas. "Visual Field Representation in Striate and Prestriate Cortices of a Prosimian Primate (Galago garnetti)". Journal of Neurophysiology 77, nr 6 (1.06.1997): 3193–217. http://dx.doi.org/10.1152/jn.1997.77.6.3193.
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Rosa, Marcello G. P., Vivien A. Casagrande, Todd Preuss, and Jon H. Kaas. Visual field representation in striate and prestriate cortices of a prosimian primate ( Galago garnetti). J. Neurophysiol. 77: 3193–3217, 1997. Microelectrode mapping techniques were used to study the visuotopic organization of the first and second visual areas (V1 and V2, respectively) in anesthetized Galago garnetti, a lorisiform prosimian primate. 1) V1 occupies ∼200 mm2 of cortex, and is pear shaped, rather than elliptical as in simian primates. Neurons in V1 form a continuous (1st-order) representation of the visual field, with the vertical meridian forming most of its perimeter. The representation of the horizontal meridian divides V1 into nearly equal sectors representing the upper quadrant ventrally, and the lower quadrant dorsally. 2) The emphasis on representation of central vision is less marked in Galago than in simian primates, both diurnal and nocturnal. The decay of cortical magnification factor with increasing eccentricity is almost exactly counterbalanced by an increase in average receptive field size, such that a point anywhere in the visual field is represented by a compartment of similar diameter in V1. 3) Although most of the cortex surrounding V1 corresponds to V2, one-quarter of the perimeter of V1 is formed by agranular cortex within the rostral calcarine sulcus, including area prostriata. Although under our recording conditions virtually every recording site in V2 yielded visually responsive cells, only a minority of those in area prostriata revealed such responses. 4) V2 forms a cortical belt of variable width, being narrowest (∼1 mm) in the representation of the area centralis and widest (2.5–3 mm) in the representation of the midperiphery (>20° eccentricity) of the visual field. V2 forms a second-order representation of the visual field, with the area centralis being represented laterally and the visual field periphery medially, near the calcarine sulcus. Unlike in simians, the line of field discontinuity in Galago V2 does not exactly coincide with the horizontal meridian: a portion of the lower quadrant immediately adjacent to the horizontal meridian is represented at the rostral border of ventral V2, instead of in dorsal V2. Despite the absence of cytochrome oxidase stripes, the visual field map in Galago V2 resembles the ones described in simians in that the magnification factor is anisotropic. 5) Receptive field progressions in cortex rostral to dorsal V2 suggest the presence of a homologue of the dorsomedial area, including representations of both quadrants of the visual field. These results indicate that many aspects of organization of V1 and V2 in simian primates are shared with lorisiform prosimians, and are therefore likely to have been present in the last common ancestor of living primates. However, some aspects of organization of the caudal visual areas in Galago are intermediate between nonprimates and simian primates, reflecting either an intermediate stage of differentiation or adaptations to a nocturnal niche. These include the shape and the small size of V1 and V2, the modest degree of emphasis on central visual field representation, and the relatively large area prostriata.
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Scholl, Benjamin, Johnathan Rylee, Jeffrey J. Luci, Nicholas J. Priebe i Jeffrey Padberg. "Orientation selectivity in the visual cortex of the nine-banded armadillo". Journal of Neurophysiology 117, nr 3 (1.03.2017): 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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Parra, Andres, Christopher A. Baker i M. McLean Bolton. "Regional Specialization of Pyramidal Neuron Morphology and Physiology in the Tree Shrew Neocortex". Cerebral Cortex 29, nr 11 (31.01.2019): 4488–505. http://dx.doi.org/10.1093/cercor/bhy326.
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Abstract The mammalian cerebral cortex is divided into different areas according to their function and pattern of connections. Studies comparing primary visual (V1) and prefrontal cortex (PFC) of primates have demonstrated striking pyramidal neuron (PN) specialization not present in comparable areas of the mouse neocortex. To better understand PFC evolution and regional PN specialization, we studied the tree shrew, a species with a close phylogenetic relationship to primates. We defined the tree shrew PFC based on cytoarchitectonic borders, thalamic connectivity and characterized the morphology and electrophysiology of layer II/III PNs in V1 and PFC. Similar to primates, the PFC PNs in the tree shrew fire with a regular spiking pattern and have larger dendritic tree and spines than those in V1. However, V1 PNs showed strikingly large basal dendritic arbors with high spine density, firing at higher rates and in a more varied pattern than PFC PNs. Yet, unlike in the mouse and unreported in the primate, medial prefrontal PN are more easily recruited than either the dorsolateral or V1 neurons. This specialization of PN morphology and physiology is likely to be a significant factor in the evolution of cortex, contributing to differences in the computational capacities of individual cortical areas.
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Srinivasan, Shyam, C. Nikoosh Carlo i Charles F. Stevens. "Predicting visual acuity from the structure of visual cortex". Proceedings of the National Academy of Sciences 112, nr 25 (8.06.2015): 7815–20. http://dx.doi.org/10.1073/pnas.1509282112.
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Three decades ago, Rockel et al. proposed that neuronal surface densities (number of neurons under a square millimeter of surface) of primary visual cortices (V1s) in primates is 2.5 times higher than the neuronal density of V1s in nonprimates or many other cortical regions in primates and nonprimates. This claim has remained controversial and much debated. We replicated the study of Rockel et al. with attention to modern stereological precepts and show that indeed primate V1 is 2.5 times denser (number of neurons per square millimeter) than many other cortical regions and nonprimate V1s; we also show that V2 is 1.7 times as dense. As primate V1s are denser, they have more neurons and thus more pinwheels than similar-sized nonprimate V1s, which explains why primates have better visual acuity.
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Roe, Anna Wang, i Daniel Y. Ts'o. "Specificity of Color Connectivity Between Primate V1 and V2". Journal of Neurophysiology 82, nr 5 (1.11.1999): 2719–30. http://dx.doi.org/10.1152/jn.1999.82.5.2719.
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To examine the functional interactions between the color and form pathways in the primate visual cortex, we have examined the functional connectivity between pairs of color oriented and nonoriented V1 and V2 neurons in Macaque monkeys. Optical imaging maps for color selectivity, orientation preference, and ocular dominance were used to identify specific functional compartments within V1 and V2 (blobs and thin stripes). These sites then were targeted with multiple electrodes, single neurons isolated, and their receptive fields characterized for orientation selectivity and color selectivity. Functional interactions between pairs of V1 and V2 neurons were inferred by cross-correlation analysis of spike firing. Three types of color interactions were studied: nonoriented V1/nonoriented V2 cell pairs, nonoriented V1/oriented V2 cell pairs, and oriented V1/nonoriented V2 cell pairs. In general, interactions between V1 and V2 neurons are highly dependent on color matching. Different cell pairs exhibited differing dependencies on spatial overlap. Interactions between nonoriented color cells in V1 and V2 are dependent on color matching but not on receptive field overlap, suggesting a role for these interactions in coding of color surfaces. In contrast, interactions between nonoriented V1 and oriented V2 color cells exhibit a strong dependency on receptive field overlap, suggesting a separate pathway for processing of color contour information. Yet another pattern of connectivity was observed between oriented V1 and nonoriented V2 cells; these cells exhibited interactions only when receptive fields were far apart and failed to interact when spatially overlapped. Such interactions may underlie the induction of color and brightness percepts from border contrasts. Our findings thus suggest the presence of separate color pathways between V1 and V2, each with differing patterns of convergence and divergence and distinct roles in color and form vision.
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Nauhaus, Ian, Kristina J. Nielsen i Edward M. Callaway. "Efficient Receptive Field Tiling in Primate V1". Neuron 91, nr 4 (sierpień 2016): 893–904. http://dx.doi.org/10.1016/j.neuron.2016.07.015.
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Palmer, Chris R., Yuzhi Chen i Eyal Seidemann. "Uniform spatial spread of population activity in primate parafoveal V1". Journal of Neurophysiology 107, nr 7 (1.04.2012): 1857–67. http://dx.doi.org/10.1152/jn.00117.2011.
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What are the shape and size of the region in primate V1 that processes information from a single point in visual space? This region, a fundamental property termed cortical point image (CPI) ( McIlwain 1986 ), represents the minimal population of V1 neurons that can be activated by a visual stimulus and therefore has important implications for population coding in the cortex. Previous indirect attempts to measure the CPI in macaque V1 using sparse microelectrode recordings resulted in conflicting findings. Whereas some early studies suggested that CPI size is constant throughout V1 (e.g., Hubel and Wiesel 1974 ), others have reported large changes in CPI size in parafoveal V1 (e.g., Van Essen et al. 1984 ). To resolve this controversy, we used voltage-sensitive dye imaging in V1 of fixating monkeys to directly measure the subthreshold CPI and several related properties across a range of parafoveal eccentricities. We found that despite large changes in other properties of the retinotopic map, the subthreshold CPI is approximately constant and extends over ∼6 × 8 mm2. This large and invariant CPI ensures a uniform representation of each point in visual space, with a complete representation of all visual features in V1, as originally proposed by Hubel and Wiesel (1974) . In addition, we found several novel and unexpected asymmetries and anisotropies in the shapes of the CPI and the population receptive field. These results expand our understanding of the representation of visual space in V1 and are likely to be relevant for the representations of stimuli in other sensory cortical areas.
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Disney, Anita A., Chiye Aoki i Michael J. Hawken. "Cholinergic suppression of visual responses in primate V1 is mediated by GABAergic inhibition". Journal of Neurophysiology 108, nr 7 (1.10.2012): 1907–23. http://dx.doi.org/10.1152/jn.00188.2012.
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Acetylcholine (ACh) has been implicated in selective attention. To understand the local circuit action of ACh, we iontophoresed cholinergic agonists into the primate primary visual cortex (V1) while presenting optimal visual stimuli. Consistent with our previous anatomical studies showing that GABAergic neurons in V1 express ACh receptors to a greater extent than do excitatory neurons, we observed suppressed visual responses in 36% of recorded neurons outside V1's primary thalamorecipient layer (4c). This suppression is blocked by the GABAA receptor antagonist gabazine. Within layer 4c, ACh release produces a response gain enhancement (Disney AA, Aoki C, Hawken MJ. Neuron 56: 701–713, 2007); elsewhere, ACh suppresses response gain by strengthening inhibition. Our finding contrasts with the observation that the dominant mechanism of suppression in the neocortex of rats is reduced glutamate release. We propose that in primates, distinct cholinergic receptor subtypes are recruited on specific cell types and in specific lamina to yield opposing modulatory effects that together increase neurons' responsiveness to optimal stimuli without changing tuning width.
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Kim, Kayeon, i Choongkil Lee. "Activity of primate V1 neurons during the gap saccade task". Journal of Neurophysiology 118, nr 2 (1.08.2017): 1361–75. http://dx.doi.org/10.1152/jn.00758.2016.
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The link between neural activity in monkey primary visual cortex (V1) and visually guided behavioral response is confirmed with the gap saccade paradigm. Results indicated that the variability in neural latency of V1 spike activity correlates with the gap effect on saccade latency and that the trial-to-trial variability in the state of V1 before the onset of saccade target correlates with the variability in neural and behavioral latencies.
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Cumming, B. G., S. J. D. Prince i A. J. Parker. "The range of disparities encoded in primate V1". Journal of Vision 1, nr 3 (14.03.2010): 271. http://dx.doi.org/10.1167/1.3.271.
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Gawne, Timothy J., i Julie M. Martin. "Activity of Primate V1 Cortical Neurons During Blinks". Journal of Neurophysiology 84, nr 5 (1.11.2000): 2691–94. http://dx.doi.org/10.1152/jn.2000.84.5.2691.
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Every time we blink our eyes, the image on the retina goes almost completely dark. And yet we hardly notice these interruptions, even though an external darkening is startling. Intuitively it would seem that if our perception is continuous, then the neuronal activity on which our perceptions are based should also be continuous. To explore this issue, we compared the responses of 63 supragranular V1 neurons recorded from two awake monkeys for four conditions: 1) constant stimulus, 2) during a reflex blink, 3) during a gap in the visual stimulus, and 4) during an external darkening when an electrooptical shutter occluded the entire scene. We show here that the activity of neurons in visual cortical area V1 is essentially shut off during a blink. In the 100-ms epoch starting 70 ms after the stimulus was interrupted, the firing rate was 27.2 ± 2.7 spikes/s (SE) for a constant stimulus, 8.2 ± 0.9 spikes/s for a reflex blink, 17.3 ± 1.9 spikes/s for a gap, and 12.7 ± 1.4 spikes/s for an external darkening. The responses during a blink are less than during an external darkening ( P < 0.05, t-test). However, many of these neurons responded with a transient burst of activity to the onset of an external darkening and not to a blink, suggesting that it is the suppression of this transient which causes us to ignore blinks. This is consistent with other studies where the presence of transient bursts of activity correlates with the perceived visibility of a stimulus.
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ZIETSCH, BRENDAN, i GUY N. ELSTON. "FRACTAL ANALYSIS OF PYRAMIDAL CELLS IN THE VISUAL CORTEX OF THE GALAGO (OTOLEMUR GARNETTI): REGIONAL VARIATION IN DENDRITIC BRANCHING PATTERNS BETWEEN VISUAL AREAS". Fractals 13, nr 02 (czerwiec 2005): 83–90. http://dx.doi.org/10.1142/s0218348x05002829.
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Previously it has been shown that the branching pattern of pyramidal cells varies markedly between different cortical areas in simian primates. These differences are thought to influence the functional complexity of the cells. In particular, there is a progressive increase in the fractal dimension of pyramidal cells with anterior progression through cortical areas in the occipitotemporal (OT) visual stream, including the primary visual area (V1), the second visual area (V2), the dorsolateral area (DL, corresponding to the fourth visual area) and inferotemporal cortex (IT). However, there are as yet no data on the fractal dimension of these neurons in prosimian primates. Here we focused on the nocturnal prosimian galago (Otolemur garnetti). The fractal dimension (D), and aspect ratio (a measure of branching symmetry), was determined for 111 layer III pyramidal cells in V1, V2, DL and IT. We found, as in simian primates, that the fractal dimension of neurons increased with anterior progression from V1 through V2, DL, and IT. Two important conclusions can be drawn from these results: (1) the trend for increasing branching complexity with anterior progression through OT areas was likely to be present in a common primate ancestor, and (2) specialization in neuron structure more likely facilitates object recognition than spectral processing.
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Marcus, Daniel S., i David C. Van Essen. "Scene Segmentation and Attention in Primate Cortical Areas V1 and V2". Journal of Neurophysiology 88, nr 5 (1.11.2002): 2648–58. http://dx.doi.org/10.1152/jn.00916.2001.
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The responses of many neurons in primary visual cortex are modulated by stimuli outside the classical receptive field in ways that may contribute to integrative processes like scene segmentation. To explore this issue, single-unit neuronal responses were recorded in monkey cortical areas V1 and V2 to visual stimuli containing either a figure or a background pattern over the receptive field. Figures were defined either by orientation contrast or by illusory contours. In all conditions, the stimulation over the RF and its nearby surround was identical. Both figure types enhanced the average population response in V1 and V2. For orientation contrast figures, enhancement averaged 50% in V2 and 30% in V1; for illusory contour figures, the enhancement averaged 24% in V2 and 18% in V1. These differences were statistically significant for figure type but not for visual area. In V2, the latency of enhancement to illusory contour-defined figures was longer than that to orientation-defined figures. Neuronal responses were recorded while the monkey performed a directed-attention task. Enhancement to both figure types was observed even when attention was directed away from the figure. Attention slightly enhanced responses in V2, independent of figure type, but did not affect responses in V1. There was no discernible effect of attention on background firing rate in either V1 or V2. These results suggest that scene segmentation is a distributed process, in which neuronal signals at successive stages of the visual hierarchy and over time increasingly reflect the global structure of the image. This process occurs independent of directed visual attention.
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Fanyiwi, Prasakti Tenri, Beshoy Agayby, Ricardo Kienitz, Marcus Haag i Michael C. Schmid. "Stimulus dependence of theta rhythmic activity in primate V1". Journal of Vision 21, nr 9 (27.09.2021): 2541. http://dx.doi.org/10.1167/jov.21.9.2541.
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Cumming, B. G. "Receptive field structure and disparity tuning in primate V1". Journal of Vision 2, nr 7 (15.03.2010): 287. http://dx.doi.org/10.1167/2.7.287.
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CASAGRANDE, V. "A third parallel visual pathway to primate area V1". Trends in Neurosciences 17, nr 7 (1994): 305–10. http://dx.doi.org/10.1016/0166-2236(94)90065-5.
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Carlson, Brock, Blake Mitchell, Jacob Westerberg i Alexander Maier. "Interocular transfer across ocular dominance columns of primate V1". Journal of Vision 22, nr 14 (5.12.2022): 4377. http://dx.doi.org/10.1167/jov.22.14.4377.
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Vanni, Simo, Henri Hokkanen, Francesca Werner i Alessandra Angelucci. "Anatomy and Physiology of Macaque Visual Cortical Areas V1, V2, and V5/MT: Bases for Biologically Realistic Models". Cerebral Cortex 30, nr 6 (2.01.2020): 3483–517. http://dx.doi.org/10.1093/cercor/bhz322.
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Abstract The cerebral cortex of primates encompasses multiple anatomically and physiologically distinct areas processing visual information. Areas V1, V2, and V5/MT are conserved across mammals and are central for visual behavior. To facilitate the generation of biologically accurate computational models of primate early visual processing, here we provide an overview of over 350 published studies of these three areas in the genus Macaca, whose visual system provides the closest model for human vision. The literature reports 14 anatomical connection types from the lateral geniculate nucleus of the thalamus to V1 having distinct layers of origin or termination, and 194 connection types between V1, V2, and V5, forming multiple parallel and interacting visual processing streams. Moreover, within V1, there are reports of 286 and 120 types of intrinsic excitatory and inhibitory connections, respectively. Physiologically, tuning of neuronal responses to 11 types of visual stimulus parameters has been consistently reported. Overall, the optimal spatial frequency (SF) of constituent neurons decreases with cortical hierarchy. Moreover, V5 neurons are distinct from neurons in other areas for their higher direction selectivity, higher contrast sensitivity, higher temporal frequency tuning, and wider SF bandwidth. We also discuss currently unavailable data that could be useful for biologically accurate models.
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Maruko, I., B. Zhang, X. Tao, J. Tong, E. L. Smith i Y. M. Chino. "Postnatal Development of Disparity Sensitivity in Visual Area 2 (V2) of Macaque Monkeys". Journal of Neurophysiology 100, nr 5 (listopad 2008): 2486–95. http://dx.doi.org/10.1152/jn.90397.2008.
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Macaque monkeys do not reliably discriminate binocular depth cues until about 8 wk of age. The neural factors that limit the development of fine depth perception in primates are not known. In adults, binocular depth perception critically depends on detection of relative binocular disparities and the earliest site in the primate visual brain where a substantial proportion of neurons are capable of discriminating relative disparity is visual area 2 (V2). We examined the disparity sensitivity of V2 neurons during the first 8 wk of life in infant monkeys and compared the responses of V2 neurons to those of V1 neurons. We found that the magnitude of response modulation in V2 and V1 neurons as a function of interocular spatial phase disparity was adult-like as early as 2 wk of age. However, the optimal spatial frequency and binocular response rate of these disparity sensitive neurons were more than an octave lower in 2- and 4-wk-old infants than in adults. Consequently, despite the lower variability of neuronal firing in V2 and V1 neurons of infant monkeys, the ability of these neurons to discriminate fine disparity differences was significantly reduced compared with adults. This reduction in disparity sensitivity of V2 and V1 neurons is likely to limit binocular depth perception during the first several weeks of a monkey's life.
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Azzi, João C. B., Ricardo Gattass, Bruss Lima, Juliana G. M. Soares i Mario Fiorani. "Precise visuotopic organization of the blind spot representation in primate V1". Journal of Neurophysiology 113, nr 10 (czerwiec 2015): 3588–99. http://dx.doi.org/10.1152/jn.00418.2014.
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The optic disk is a region of the retina consisting mainly of ganglion cell axons and blood vessels, which generates a visual scotoma known as the blind spot (BS). Information present in the surroundings of the BS can be used to complete the missing information. However, the neuronal mechanisms underlying these perceptual phenomena are poorly understood. We investigate the topography of the BS representation (BSR) in cortical area V1 of the capuchin monkey, using single and multiple electrodes. Receptive fields (RFs) of neurons inside the BSR were investigated using two distinct automatic bias-free mapping methods. The first method (local mapping) consisted of randomly flashing small white squares. For the second mapping method (global mapping), we used a single long bar that moved in one of eight directions. The latter stimulus was capable of eliciting neuronal activity inside the BSR, possibly attributable to long-range surround activity taking place outside the borders of the BSR. Importantly, we found that the neuronal activity inside the BSR is organized topographically in a manner similar to that found in other portions of V1. On average, the RFs inside the BS were larger than those outside. However, no differences in orientation or direction tuning were found between the two regions. We propose that area V1 exhibits a continuous functional topographic map, which is not interrupted in the BSR, as expected by the distribution of photoreceptors in the retina. Thus V1 topography is better described as “visuotopic” rather than as a discontinuous “retinotopic” map.
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Jazayeri, Mehrdad, Zachary Lindbloom-Brown i Gregory D. Horwitz. "Saccadic eye movements evoked by optogenetic activation of primate V1". Nature Neuroscience 15, nr 10 (2.09.2012): 1368–70. http://dx.doi.org/10.1038/nn.3210.
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Bradley, D. C., P. R. Troyk, J. A. Berg, M. Bak, S. Cogan, R. Erickson, C. Kufta i in. "Visuotopic Mapping Through a Multichannel Stimulating Implant in Primate V1". Journal of Neurophysiology 93, nr 3 (marzec 2005): 1659–70. http://dx.doi.org/10.1152/jn.01213.2003.
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We report on our efforts to establish an animal model for the development and testing of a cortical visual prostheses. One-hundred-fifty-two electrodes were implanted in the primary visual cortex of a rhesus monkey. The electrodes were made from iridium with an activated iridium oxide film, which has a large charge capacity for a given surface area, and insulated with parylene-C. One-hundred-fourteen electrodes were functional after implantation. The activity of small (2–3) neuronal clusters was first recorded to map the visually responsive region corresponding to each electrode. The animal was then trained in a memory (delayed) saccade task, first with a visual target, then to a target defined by direct cortical stimulation with coordinates specified by the stimulating electrode's mapped receptive field. The SD of saccade endpoints was ∼2.5 larger for electrically stimulated versus visual saccades; nevertheless, when trial-to-trial scatter was averaged out, the correlation between saccade end points and receptive field locations was highly significant and approached unity after several months of training. Five electrodes were left unused until the monkey was fully trained; when these were introduced, the receptive field-saccade correlations were high on the first day of use ( R = 0.85, P = 0.03 for angle, R = 0.98, P < 0.001 for eccentricity), indicating that the monkey had not learned to perform the task empirically by memorizing reward zones. The results of this experiment suggest the potential for rigorous behavioral testing of cortical visual prostheses in the macaque.
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Lourens, Tino, i Emilia Barakova. "Orientation contrast sensitive cells in primate V1 a computational model". Natural Computing 6, nr 3 (12.04.2007): 241–52. http://dx.doi.org/10.1007/s11047-006-9023-7.
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Mundinano, Inaki-Carril, William C. Kwan i James A. Bourne. "Retinotopic specializations of cortical and thalamic inputs to area MT". Proceedings of the National Academy of Sciences 116, nr 46 (28.10.2019): 23326–31. http://dx.doi.org/10.1073/pnas.1909799116.
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Retinotopic specializations in the ventral visual stream, especially foveal adaptations, provide primates with high-acuity vision in the central visual field. However, visual field specializations have not been studied in the dorsal visual stream, dedicated to processing visual motion and visually guided behaviors. To investigate this, we injected retrograde neuronal tracers occupying the whole visuotopic representation of the middle temporal (MT) visual area in marmoset monkeys and studied the distribution and morphology of the afferent primary visual cortex (V1) projections. Contrary to previous reports, we found a heterogeneous population of V1-MT projecting neurons distributed in layers 3C and 6. In layer 3C, spiny stellate neurons were distributed mainly in foveal representations, while pyramidal morphologies were characteristic of peripheral eccentricities. This primate adaptation of the V1 to MT pathway is arranged in a way that we had not previously understood, with abundant stellate projection neurons in the high-resolution foveal portions, suggesting rapid relay of motion information to visual area MT. We also describe that the medial portion of the inferior pulvinar (PIm), which is the main thalamic input to area MT, shows a retinotopic organization, likely reflecting the importance of this pathway during development and the establishment of area MT topography.
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Garg, Anupam K., Peichao Li, Mohammad S. Rashid i Edward M. Callaway. "Color and orientation are jointly coded and spatially organized in primate primary visual cortex". Science 364, nr 6447 (27.06.2019): 1275–79. http://dx.doi.org/10.1126/science.aaw5868.
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Previous studies support the textbook model that shape and color are extracted by distinct neurons in primate primary visual cortex (V1). However, rigorous testing of this model requires sampling a larger stimulus space than previously possible. We used stable GCaMP6f expression and two-photon calcium imaging to probe a very large spatial and chromatic visual stimulus space and map functional microarchitecture of thousands of neurons with single-cell resolution. Notable proportions of V1 neurons strongly preferred equiluminant color over achromatic stimuli and were also orientation selective, indicating that orientation and color in V1 are mutually processed by overlapping circuits. Single neurons could precisely and unambiguously code for both color and orientation. Further analyses revealed systematic spatial relationships between color tuning, orientation selectivity, and cytochrome oxidase histology.
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Milner, A. D. "Is visual processing in the dorsal stream accessible to consciousness?" Proceedings of the Royal Society B: Biological Sciences 279, nr 1737 (28.03.2012): 2289–98. http://dx.doi.org/10.1098/rspb.2011.2663.
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There are two highly interconnected clusters of visually responsive areas in the primate cortex. These two clusters have relatively few interconnections with each other, though those interconnections are undoubtedly important. One of the two main clusters (the dorsal stream) links the primary visual cortex (V1) to superior regions of the occipito-parietal cortex, while the other (the ventral stream) links V1 to inferior regions of the occipito-temporal cortex. According to our current understanding of the functional anatomy of these two systems, the dorsal stream's principal role is to provide real-time ‘bottom-up’ visual guidance of our movements online. In contrast, the ventral stream, in conjunction with top-down information from visual and semantic memory, provides perceptual representations that can serve recognition, visual thought, planning and memory offline. In recent years, this interpretation, initially based chiefly on studies of non-human primates and human neurological patients, has been well supported by functional MRI studies in humans. This perspective presents empirical evidence for the contention that the dorsal stream governs the visual control of movement without the intervention of visual awareness.
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Jones, H. E., W. Wang i A. M. Sillito. "Spatial Organization and Magnitude of Orientation Contrast Interactions in Primate V1". Journal of Neurophysiology 88, nr 5 (1.11.2002): 2796–808. http://dx.doi.org/10.1152/jn.00403.2001.
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We have explored the spatial organization of orientation contrast effects in primate V1. Our stimuli were either concentric patches of drifting grating of varying orientation and diameter or grating patches displaced in x–y coordinates around a central patch overlying the classical receptive field (CRF). All cells in the sample exhibited response suppression to iso-oriented stimuli exceeding the CRF. Changing the outer stimulus orientation revealed five response patterns: 1) orientation alignment suppression (17% of cells)—a suppressive component tuned to the same orientation as the cell's optimal, 2) orientation contrast facilitation (63%)—responses to orientation contrast stimuli exceeded those to the center stimulus alone, 3) nonorientation specific suppression (3%), 4) mixed general suppression and alignment suppression (14%), and 5) orientation contrast suppression (14%)—cross-oriented stimuli evoked stronger suppression than iso-oriented stimuli. Thus most cells (94%) showed larger responses to orientation contrast stimuli than to iso-oriented stimuli, and over one-half showed orientation contrast facilitation. There appeared to be a spatially structured organization of the zones driving the different response patterns with respect to the CRF. Nonorientation-specific suppression and orientation contrast suppression were predominantly evoked by orientation contrast borders located within the CRF, and orientation contrast facilitation was mainly driven by surround stimuli lying outside the CRF. This led to different response patterns according to border location. Zones driving orientation contrast facilitation were not necessarily contiguous to, nor uniformly distributed around, the CRF. Our data support two processes underlying orientation contrast enhancement effects: a simple variation in the strength of surround suppression drawing on the fact that surround suppression is tuned to the same orientation as the CRF and a second process driven by orientation contrast that enhanced cells' responses to CRF stimulation by either dis-inhibition or orientation contrast facilitation. We suggest these processes may serve to enhance response levels to salient image features such as junctions and corners and may contribute to orientation pop-out.
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Dragoi MIT, V., J. Sharma, E. K. Miller i M. Sur. "Dynamics of neuronal sensitivity in primate V1 underlying local feature discrimination". Journal of Vision 2, nr 7 (15.03.2010): 126. http://dx.doi.org/10.1167/2.7.126.
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Celebrini, Simona, Simon Thorpe, Yves Trotter i Michel Imbert. "Dynamics of orientation coding in area V1 of the awake primate". Visual Neuroscience 10, nr 5 (wrzesień 1993): 811–25. http://dx.doi.org/10.1017/s0952523800006052.
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AbstractTo investigate the importance of feedback loops in visual information processing, we have analyzed the dynamic aspects of neuronal responses to oriented gratings in cortical area V1 of the awake primate. If recurrent feedback is important in generating orientation selectivity, the initial part of the neuronal response should be relatively poorly selective, and full orientation selectivity should only appear after a delay. Thus, by examining the dynamics of the neuronal responses it should be possible to assess the importance of feedback processes in the development of orientation selectivity. The results were base on a sample of 259 cells recorded in two monkeys, of which 89% were visually responsive. Of these, approximately two-thirds were orientation selective. Response latency varied considerably between neurons, ranging from a minimum of 41 ms to over 150 ms, although most had latencies of 50–70 ms. Orientation tuning (defined as the bandwidth at half-height) ranged from 16 deg to over 90 deg, with a mean value of around 55 deg. By examining the selectivity of these different neurons by 10-ms time slices, starting at the onset of the neuronal response, we found that the orientation selectivity of virtually every neuron was fully developed at the very start of the neuronal response. Indeed, many neurons showed a marked tendency to respond at somewhat longer latencies to stimuli that were nonoptimally oriented, with the result that orientation selectivity was highest at the very start of the neuronal response. Furthermore, there was no evidence that the neurons with the shortest onset latencies were less selective. Such evidence is inconsistent with the hypothesis that recurrent intracortical feedback plays an important role in the generation of orientation selectivity. Instead, we suggest that orientation selectivity is primarily generated using feedforward mechanisms, including feedforward inhibition. Such a strategy has the advantage of allowing orientation to be computed rapidly, and avoids the initially poorly selective neuronal responses that characterize processing involving recurrent loops.
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Durand, Jean-Baptiste, Yves Trotter i Simona Celebrini. "Privileged Processing of the Straight-Ahead Direction in Primate Area V1". Neuron 66, nr 1 (kwiecień 2010): 126–37. http://dx.doi.org/10.1016/j.neuron.2010.03.014.
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Li, X., Y. Chen, R. Lashgari, Y. Bereshpolova, H. A. Swadlow, B. B. Lee i J. M. Alonso. "Mixing of Chromatic and Luminance Retinal Signals in Primate Area V1". Cerebral Cortex 25, nr 7 (23.01.2014): 1920–37. http://dx.doi.org/10.1093/cercor/bhu002.
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Roe, Anna W., i Daniel Y. Ts'o. "Specificity of V1–V2 orientation networks in the primate visual cortex". Cortex 72 (listopad 2015): 168–78. http://dx.doi.org/10.1016/j.cortex.2015.07.007.
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Berens, P., A. S. Ecker, R. J. Cotton, W. J. Ma, M. Bethge i A. S. Tolias. "A Fast and Simple Population Code for Orientation in Primate V1". Journal of Neuroscience 32, nr 31 (1.08.2012): 10618–26. http://dx.doi.org/10.1523/jneurosci.1335-12.2012.
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Caywood, Matthew S., Benjamin Willmore i David J. Tolhurst. "Independent Components of Color Natural Scenes Resemble V1 Neurons in Their Spatial and Color Tuning". Journal of Neurophysiology 91, nr 6 (czerwiec 2004): 2859–73. http://dx.doi.org/10.1152/jn.00775.2003.
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It has been hypothesized that mammalian sensory systems are efficient because they reduce the redundancy of natural sensory input. If correct, this theory could unify our understanding of sensory coding; here, we test its predictions for color coding in the primate primary visual cortex (V1). We apply independent component analysis (ICA) to simulated cone responses to natural scenes, obtaining a set of colored independent component (IC) filters that form a redundancy-reducing visual code. We compare IC filters with physiologically measured V1 neurons, and find great spatial similarity between IC filters and V1 simple cells. On cursory inspection, there is little chromatic similarity; however, we find that many apparent differences result from biases in the physiological measurements and ICA analysis. After correcting these biases, we find that the chromatic tuning of IC filters does indeed resemble the population of V1 neurons, supporting the redundancy-reduction hypothesis.
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Zogopoulos, G., P. Nathanielsz, GN Hendy i CG Goodyer. "The baboon: a model for the study of primate growth hormone receptor gene expression during development". Journal of Molecular Endocrinology 23, nr 1 (1.08.1999): 67–75. http://dx.doi.org/10.1677/jme.0.0230067.
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In subprimates, significant onset of growth hormone receptor (GHR) expression occurs only after birth whereas, in the human, GHR mRNA and protein are widely manifest from the first trimester of fetal life. Thus, it is likely that subprimates are not the best models for studying regulation of human GHR gene transcription, especially during early stages in development. Here we have explored the potential of the baboon as a more appropriate model. Baboon GHR cDNAs were cloned from postnatal liver by reverse transcription (RT)-PCR, using human GHR-specific primers. The encoded baboon GHR precursor protein has an identical signal peptide sequence to that of human and rhesus monkey GHRs, and the mature baboon GHR is also 620 amino acids long, with 95% and 98.5% amino acid identity to the human and rhesus monkey receptors respectively. Previous studies in the human have identified eight 5' untranslated region (5' UTR) variants of the GHR mRNA (V1 to V8, numbered according to their relative abundance). We cloned the baboon V1, V3 and V4 homologues by RT-PCR: these variants have a high degree (>92%) of sequence identity with their human counterparts and also diverge at an identical point, 12 nucleotides upstream of the start of translation. The expression pattern of these three GHR mRNA isoforms in baboon liver during development was characterized. Strong expression of baboon V1 and V4 was evident by 49 days of postnatal life (n=5, 49 days and adult (18.6-19.6 kg)); very low levels of V1, but not V4, were observed in younger animals (n=2, 6 and 30 days). In contrast, V3 5' UTR variant mRNA was present in all fetal (n=4, 141-155 days gestation) and postnatal (n=7, 6-19.6 days and adult (18.6 kg)) hepatic specimens examined. Analysis of postnatal kidney and lung (n=2, 19 and 19.6 kg) revealed that V3 transcripts are present in these tissues, but not V1 and V4. Together, these data demonstrate that, as in the human, baboon V1 and V4 expression is developmentally regulated and tissue specific, while the V3 isoform is more widely expressed. Therefore, it is likely that the regulatory regions of the baboon and human GHR genes are well conserved. Our findings suggest that the baboon is an appropriate animal model in which to define the mechanisms regulating GHR gene transcription during primate development.
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WEBB, BEN S., CHRIS J. TINSLEY, NICK E. BARRACLOUGH, AMANDA PARKER i ANDREW M. DERRINGTON. "Gain control from beyond the classical receptive field in primate primary visual cortex". Visual Neuroscience 20, nr 3 (maj 2003): 221–30. http://dx.doi.org/10.1017/s0952523803203011.
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Gain control is a salient feature of information processing throughout the visual system. Heeger (1991, 1992) described a mechanism that could underpin gain control in primary visual cortex (V1). According to this model, a neuron's response is normalized by dividing its output by the sum of a population of neurons, which are selective for orientations covering a broad range. Gain control in this scheme is manifested as a change in the semisaturation constant (contrast gain) of a V1 neuron. Here we examine how flanking and annular gratings of the same or orthogonal orientation to that preferred by a neuron presented beyond the receptive field modulate gain in V1 neurons in anesthetized marmosets (Callithrix jacchus). To characterize how gain was modulated by surround stimuli, the Michaelis–Menten equation was fitted to response versus contrast functions obtained under each stimulus condition. The modulation of gain by surround stimuli was modelled best as a divisive reduction in response gain. Response gain varied with the orientation of surround stimuli, but was reduced most when the orientation of a large annular grating beyond the classical receptive field matched the preferred orientation of neurons. The strength of surround suppression did not vary significantly with retinal eccentricity or laminar distribution. In the marmoset, as in macaques (Angelucci et al., 2002a, b), gain control over the sort of distances reported here (up to 10 deg) may be mediated by feedback from extrastriate areas.
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Nassi, J. J., S. G. Lomber i R. T. Born. "Corticocortical Feedback Contributes to Surround Suppression in V1 of the Alert Primate". Journal of Neuroscience 33, nr 19 (8.05.2013): 8504–17. http://dx.doi.org/10.1523/jneurosci.5124-12.2013.
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Bock, Nicholas A., Ara Kocharyan i Afonso C. Silva. "Manganese-enhanced MRI visualizes V1 in the non-human primate visual cortex". NMR in Biomedicine 22, nr 7 (sierpień 2009): 730–36. http://dx.doi.org/10.1002/nbm.1384.
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Yin, Jiapeng, Hongliang Gong, Xu An, Zheyuan Chen, Yiliang Lu, Ian M. Andolina, Niall McLoughlin i Wei Wang. "Breaking cover: neural responses to slow and fast camouflage-breaking motion". Proceedings of the Royal Society B: Biological Sciences 282, nr 1813 (22.08.2015): 20151182. http://dx.doi.org/10.1098/rspb.2015.1182.
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Primates need to detect and recognize camouflaged animals in natural environments. Camouflage-breaking movements are often the only visual cue available to accomplish this. Specifically, sudden movements are often detected before full recognition of the camouflaged animal is made, suggesting that initial processing of motion precedes the recognition of motion-defined contours or shapes. What are the neuronal mechanisms underlying this initial processing of camouflaged motion in the primate visual brain? We investigated this question using intrinsic-signal optical imaging of macaque V1, V2 and V4, along with computer simulations of the neural population responses. We found that camouflaged motion at low speed was processed as a direction signal by both direction- and orientation-selective neurons, whereas at high-speed camouflaged motion was encoded as a motion-streak signal primarily by orientation-selective neurons. No population responses were found to be invariant to the camouflage contours. These results suggest that the initial processing of camouflaged motion at low and high speeds is encoded as direction and motion-streak signals in primate early visual cortices. These processes are consistent with a spatio-temporal filter mechanism that provides for fast processing of motion signals, prior to full recognition of camouflage-breaking animals.
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RISNER, MICHAEL L., i TIMOTHY J. GAWNE. "The response dynamics of primate visual cortical neurons to simulated optical blur". Visual Neuroscience 26, nr 4 (lipiec 2009): 411–20. http://dx.doi.org/10.1017/s0952523809990174.
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AbstractNeurons in visual cortical area V1 typically respond well to lines or edges of specific orientations. There have been many studies investigating how the responses of these neurons to an oriented edge are affected by changes in luminance contrast. However, in natural images, edges vary not only in contrast but also in the degree of blur, both because of changes in focus and also because shadows are not sharp. The effect of blur on the response dynamics of visual cortical neurons has not been explored. We presented luminance-defined single edges in the receptive fields of parafoveal (1–6 deg eccentric) V1 neurons of two macaque monkeys trained to fixate a spot of light. We varied the width of the blurred region of the edge stimuli up to 0.36 deg of visual angle. Even though the neurons responded robustly to stimuli that only contained high spatial frequencies and 0.36 deg is much larger than the limits of acuity at this eccentricity, changing the degree of blur had minimal effect on the responses of these neurons to the edge. Primates need to measure blur at the fovea to evaluate image quality and control accommodation, but this might only involve a specialist subpopulation of neurons. If visual cortical neurons in general responded differently to sharp and blurred stimuli, then this could provide a cue for form perception, for example, by helping to disambiguate the luminance edges created by real objects from those created by shadows. On the other hand, it might be important to avoid the distraction of changing blur as objects move in and out of the plane of fixation. Our results support the latter hypothesis: the responses of parafoveal V1 neurons are largely unaffected by changes in blur over a wide range.
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Goodyer, CG, H. Zheng i GN Hendy. "Alu elements in human growth hormone receptor gene 5' untranslated region exons". Journal of Molecular Endocrinology 27, nr 3 (1.12.2001): 357–66. http://dx.doi.org/10.1677/jme.0.0270357.
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The human growth hormone receptor (hGHR) is encoded by exons 2-10 of the hGHR gene on chromosome 5p13.1-p12. There are several different 5' untranslated region (5'UTR) variants of hGHR mRNA (V1-V9) that all encode the same protein. We have recently mapped the V1-V9 5'UTR sequences within 40 kb of the 5' flanking region of the hGHR gene. Seven of the exons are clustered within two small modules, module A (V2-V9-V3) and module B (V7-V1-V4-V8), approximately 38 kb and approximately 18 kb respectively upstream of exon 2 of the coding region; V6 lies midway between the two modules and V5 is adjacent to exon 2. We now report the existence of two subvariant V3 exons, one upstream of module A (exon V3b) and one midway between module B and exon 2 (exon V3a/b). Both have sequences homologous to Alu elements. In addition, we determined the alternative splicing mechanisms that produce three different mRNAs from these exons: V3c (from the V3 exon in module A) or V3a and V3b (from a combination of exon V3 and the Alu-containing V3 subvariant exons). hGHR expression is under developmental- and tissue-specific regulation: module A-derived mRNAs are widely expressed in human tissues, while module B-derived mRNAs are only detectable in postnatal liver. Expression of the variant V3 mRNAs is similar to those from module A, being produced ubiquitously in human fetal and postnatal tissues, with V3c always the major variant detected. The Alu-containing mRNAs (V3a and V3b) are also detectable in baboon and rhesus tissues, in accordance with the finding of Alu elements throughout the primate genome. In summary, we have mapped the relative locations of two new 5'UTR exons within the 5' flanking region of the hGHR gene and described the derivation and expression patterns for two variant hGHR mRNAs from these primate-specific exons. The introduction of Alu elements has contributed to the evolution of the primate GHR gene as a highly complex transcriptional unit.
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Schira, Mark M., Alex R. Wade i Christopher W. Tyler. "Two-Dimensional Mapping of the Central and Parafoveal Visual Field to Human Visual Cortex". Journal of Neurophysiology 97, nr 6 (czerwiec 2007): 4284–95. http://dx.doi.org/10.1152/jn.00972.2006.
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Primate visual cortex contains a set of maps of visual space. These maps are fundamental to early visual processing, yet their form is not fully understood in humans. This is especially true for the central and most important part of the visual field—the fovea. We used functional magnetic resonance imaging (fMRI) to measure the mapping geometry of human V1 and V2 down to 0.5° of eccentricity. By applying automated atlas fitting procedures to parametrize and average retinotopic measurements of eight brains, we provide a reference standard for the two-dimensional geometry of human early visual cortex of unprecedented precision and analyze this high-quality mean dataset with respect to the 2-dimensional cortical magnification morphometry. The analysis indicates that 1) area V1 has meridional isotropy in areal projection: equal areas of visual space are mapped to equal areas of cortex at any given eccentricity. 2) V1 has a systematic pattern of local anisotropies: cortical magnification varies between isopolar and isoeccentricity lines, and 3) the shape of V1 deviates systematically from the complex-log model, the fit of which is particularly poor close to the fovea. We therefore propose that human V1 be fitted by models based on an equal-area principle of its two-dimensional magnification. 4) V2 is elongated by a factor of 2 in eccentricity direction relative to V1 and has significantly more local anisotropy. We propose that V2 has systematic intrinsic curvature, but V1 is intrinsically flat.
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Shi, Li, Qi Ming Ye i Xiao Ke Niu. "Orientation Coding by Population of Neurons in Rats' Primary Visual Cortex". Applied Mechanics and Materials 427-429 (wrzesień 2013): 2089–93. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.2089.
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Research on Primate visual cortex (V1 area) neurons orientation coding mechanism is the base of revealing the whole visual cortex information processing mechanism. Firstly, this paper adopted different orientation grating to stimulate visually on rats. Meanwhile, gather response signals of population neurons from V1 area using multi-electrode arrays. Then, screen effective response channels according to the orientation selection of different neurons in different channels. Besides, extract Spike average fire rate and LFPγ band power feature in every effective channel signals within specific stimulus response time to construct population response joint features. Finally, taking Lasso regression model as coding model, use joint features to differentiate grating orientation, in order to research on V1 areas population neurons orientation coding. The consequences indicate that the results of population response joint features coding for six different orientation are superior to the results of any single feature of population response coding, and remarkably better than the results of single channel response feature coding.
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Scholl, Benjamin, Johannes Burge i Nicholas J. Priebe. "Binocular integration and disparity selectivity in mouse primary visual cortex". Journal of Neurophysiology 109, nr 12 (15.06.2013): 3013–24. http://dx.doi.org/10.1152/jn.01021.2012.
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Signals from the two eyes are first integrated in primary visual cortex (V1). In many mammals, this binocular integration is an important first step in the development of stereopsis, the perception of depth from disparity. Neurons in the binocular zone of mouse V1 receive inputs from both eyes, but it is unclear how that binocular information is integrated and whether this integration has a function similar to that found in other mammals. Using extracellular recordings, we demonstrate that mouse V1 neurons are tuned for binocular disparities, or spatial differences, between the inputs from each eye, thus extracting signals potentially useful for estimating depth. The disparities encoded by mouse V1 are significantly larger than those encoded by cat and primate. Interestingly, these larger disparities correspond to distances that are likely to be ecologically relevant in natural viewing, given the stereo-geometry of the mouse visual system. Across mammalian species, it appears that binocular integration is a common cortical computation used to extract information relevant for estimating depth. As such, it is a prime example of how the integration of multiple sensory signals is used to generate accurate estimates of properties in our environment.