Academic literature on the topic 'Orientation/direction selectivity'
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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.
Full textAbstract:
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.
Full textAbstract:
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.
Full textAbstract:
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.
Full textAbstract:
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.
Full textAbstract:
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.
Full textAbstract:
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.
Full textAbstract:
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.
Full textAbstract:
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.
Full textAbstract:
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.
Full textAbstract:
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)
Dissertations / Theses on the topic "Orientation/direction selectivity"
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Kim, Jong-Nam. "Orientation and direction selectivity of cat striate cortical neurones : suppressive mechanisms revealed by binocular conditioning." Thesis, Keele University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384824.
Full textBook chapters on the topic "Orientation/direction selectivity"
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Braddick, Oliver, Janette Atkinson, and John Wattam-Bell. "Development of Visual Cortical Selectivity: Binocularity, Orientation and Direction of Motion." In Neurobiology of Early Infant Behaviour, 165–72. London: Macmillan Education UK, 1989. http://dx.doi.org/10.1007/978-1-349-10735-3_16.
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Karla, Ana, Cecilia Ceriatte, Bruss Lima, Juliana Soares, Mario Fiorani, and Ricardo Gattass. "The Role of Cortical Feedback Circuitry on Functional Maps of V2 in Primates: Effects on Orientation Tuning and Direction Selectivity." In Functional Brain Mapping and the Endeavor to Understand the Working Brain. InTech, 2013. http://dx.doi.org/10.5772/56497.
Full textConference papers on the topic "Orientation/direction selectivity"
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Garland, Anthony, and Georges Fadel. "Optimal Design of Topology and Gradient Orthotropic Material." In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-67852.
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The goal of this research is to optimize an object’s macroscopic topology and gradient material properties subject to multiple loading conditions. The gradient material is modeled as an orthotropic material where the elastic modulus in the x and y directions can change in addition to rotating the orthotropic material to align with the loading condition at each point. This orthotropic material is similar to a fiber-reinforced material where the number of fibers in the x and y-directions can change at each point as well as the overall rotation of the material at each point. Repeating cellular unit cells which form a mesostructure can also achieve these customized orthotropic material properties. Homogenization theory allows calculating the macroscopic averaged bulk properties of these celluar materials. The mesostructures are an order of magnitude smaller than the macro structure which then allows small variations in strain and stress to be averaged out. The average (homogenized) properties of a group of these mesostructures can be customized by carefully designing the topology of the repeating unit cell used to make the mesostructure. In the past, gradient material optimization coupled to optimal fiber optimization has been used to design material properties within a single part. By combining topology optimization with gradient material optimization and fiber orientation optimization, the algorithm significantly decreases the objective, which is to minimize the strain energy of the object. Additive manufacturing techniques enable the fabrication of these designs by selectively placing reinforcing fibers or by printing different mesostructures in each region of the design. Finally, this work shows a comparison of simple topology optimization, topology optimization with isotropic gradient materials, and topology optimization with orthotropic gradient materials.