Topographical representations of mental images in primary visual cortex

Article Abstract:

Visualizing objects with the eyes closed stimulates the primary visual cortex. Researchers used PET imaging to analyze blood flow in the brains of five male volunteers under different conditions of visualization. The size of the image correlated with the location of maximal activation due to spatial distribution of visual areas. A comparison between two baselines indicates high blood flow during the resting baseline in area 17 of the primary visual cortex. Thus, visual mental imagery entails depictive representation, not just linguistic description.

Images, Optical, Optical images

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Orientation selectivity of thalamic input to simple cells of cat visual cortex

Article Abstract:

Cooling of the visual cortex has negligible influence on the orientation tuning of visually evoked synaptic potentials in cats. Cooling significantly alters the activity in the local cortical circuit below the cooling plate, but leaves the geniculate synaptic input functional. Orientation selectivity originates from cortical inhibitory interaction and selective amplification of geniculate inputs by feedback mechanisms. The lateral geniculate nucleus is involved in 21% to 63% of visually evoked responses.

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A sense of direction

Article Abstract:

The reason for the unusual morphology of the Meynert cells in the brain has long been considered but a new study suggests that the curiously shaped neurons contribute to the cells' sensitivity to visual motion, particularly direction selectivity. The key to the theory is the cortical retinotopic map, with each point in the cortex receiving input from a reciprocal point in the visual cortex to form an orderly, two-dimensional map of the visual field.

Research, Models, Brain research, Cerebral cortex

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