Cortical mechanisms for local and global analysis of visual space in the cat

The effects of lesions in the striate or extra-striate visual cortex of cats were evaluated using visual discrimination problems which required either local or global pattern processing. The results indicate that damage to areas 17 and 18 preferentially impairs local processes, while in addition they suggest that damage to the extra-striate cortex preferentially affects global processing. These findings may be related to the observations that cats with large lesions in the extra-striate cortex demonstrate deficits in form perception without reductions in visual acuity and those with lesions in areas 17-18 show elevations of acuity thresholds while maintaining excellent pattern and form vision.