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Retinotopic Map (retinotopic + map)
Selected Abstracts2126: Retinal and cortical functions in adult mice lacking cannabinoid receptorsACTA OPHTHALMOLOGICA, Issue 2010C CASANOVA Purpose Cannabinoid receptor type 1 (CB1R) has been localized in the adult retina of rodents. It is expressed in cones, horizontal, bipolar, some amacrine and ganglion cells. The expression of the cannabinoid receptor type 2 (CB2R) mRNA in the retina of adult rats was also reported. The goal of the present study was to investigate the functional roles of CB1R and CB2R in the retina by comparing retinal electrophysiological responses and cortical optical signals in normal and genetically modified mice. Methods Experiments were conducted on four different groups of C57BL/6 mice: CB1R wild type (WT), CB1R knockout (KO), CB2R WT and KO. Scotopic electroretinograms (ERG) luminance-response functions and photopic ERGs were recorded. In a subset of CB1 groups, intrinsic signals acquired by optical brain imaging were used to determine spatial frequency, contrast sensitivity and retinotopic maps in the visual cortex. Results The CB1R KO retina showed a stronger photopic response. No differences were observed for scotopic responses. For the CB2R groups, the scotopic b-wave response was stronger in the KO mice. No differences could be seen between visual cortices maps with respect to SF and contrast sensitivity. Retinotopic maps differed only along the azimuth. Significant differences were observed between hemodynamic response functions. Conclusion These results indicate that CB receptors can play a regulatory effect on the neurovascular coupling at the retinal and cortical levels and on the functional organization of the mice visual cortex along the azimuth Axis.(NSERC) [source] The fidelity of the cortical retinotopic map in human amblyopiaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Xingfeng Li Abstract To delineate the fidelity of the functional cortical organization in humans with amblyopia, we undertook an investigation into how spatial information is mapped across the visual cortex in amblyopic observers. We assessed whether the boundaries of the visual areas controlled by the amblyopic and fellow fixing eye are in the same position, the fidelity of the retinotopic map within different cortical areas and the average receptive field size in different visual areas. The functional organization of the visual cortex was reconstructed using a fMRI phase-encoded retinotopic mapping analysis. This method sequentially stimulates each point in the visual field along the axes of a polar-coordinate system, thereby reconstructing the representation of the visual field on the cortex. We found that the cortical areas were very similar in normals and amblyopes, with only small differences in boundary positions of different visual areas between fixing and fellow amblyopic eye activation. Within these corresponding visual areas, we did find anomalies in retinotopy in some but not all amblyopes that were not simply a consequence of the poorer functional responses and affected central and peripheral field regions. Only a small increase in the average (or collective) receptive field size was found for full-field representation in amblyopes and none at all for central field representation. The former may simply be a consequence of the poorer functional responses. [source] Immunohistochemical parcellation of the ferret (Mustela putorius) visual cortex reveals substantial homology with the cat (Felis catus)THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 21 2010Jihane Homman-Ludiye Abstract Electrophysiological mapping of the adult ferret visual cortex has until now determined the existence of 12 retinotopically distinct areas; however, in the cat, another member of the Carnivora, 20 distinct visual areas have been identified by using retinotopic mapping and immunolabeling. In the present study, the immunohistochemical approach to demarcate the areal boundaries of the adult ferret visual cortex was applied in order to overcome the difficulties in accessing the sulcal surfaces of a small, gyrencephalic brain. Nonphosphorylated neurofilament (NNF) expression profiles were compared with another classical immunostain of cortical nuclei, Cat-301 chondroitin sulfate proteoglycan (CSPG). Together, these two markers reliably demarcated the borders of the 12 previously defined areas and revealed further arealization beyond those borders to a total of 19 areas: 21a and 21b; the anterolateral, posterolateral, dorsal, and ventral lateral suprasylvian areas (ALLS, PLLS, DLS, and VLS, respectively); and the splenial and cingulate visual areas (SVA and CVA). NNF expression profile and location of the newly defined areas correlate with previously defined areas in the cat. Moreover, NNF and Cat-301 together revealed discrete expression domains in the posteroparietal (PP) cortex, demarcating four subdivisions in the caudal lateral and medial domains (PPcL and PPcM) and rostral lateral and medial domains (PPrL and PPrM), where only two retinotopic maps have been previously identified (PPc and PPr). Taken together, these studies suggest that NNF and Cat-301 can illustrate the homology between cortical areas in different species and draw out the principles that have driven evolution of the visual cortex. J. Comp. Neurol. 518:4439,4462, 2010. © 2010 Wiley-Liss, Inc. [source] 2126: Retinal and cortical functions in adult mice lacking cannabinoid receptorsACTA OPHTHALMOLOGICA, Issue 2010C CASANOVA Purpose Cannabinoid receptor type 1 (CB1R) has been localized in the adult retina of rodents. It is expressed in cones, horizontal, bipolar, some amacrine and ganglion cells. The expression of the cannabinoid receptor type 2 (CB2R) mRNA in the retina of adult rats was also reported. The goal of the present study was to investigate the functional roles of CB1R and CB2R in the retina by comparing retinal electrophysiological responses and cortical optical signals in normal and genetically modified mice. Methods Experiments were conducted on four different groups of C57BL/6 mice: CB1R wild type (WT), CB1R knockout (KO), CB2R WT and KO. Scotopic electroretinograms (ERG) luminance-response functions and photopic ERGs were recorded. In a subset of CB1 groups, intrinsic signals acquired by optical brain imaging were used to determine spatial frequency, contrast sensitivity and retinotopic maps in the visual cortex. Results The CB1R KO retina showed a stronger photopic response. No differences were observed for scotopic responses. For the CB2R groups, the scotopic b-wave response was stronger in the KO mice. No differences could be seen between visual cortices maps with respect to SF and contrast sensitivity. Retinotopic maps differed only along the azimuth. Significant differences were observed between hemodynamic response functions. Conclusion These results indicate that CB receptors can play a regulatory effect on the neurovascular coupling at the retinal and cortical levels and on the functional organization of the mice visual cortex along the azimuth Axis.(NSERC) [source] | ||||||||||