PRESERVATION OF POINTING ACCURACY TOWARD MOVING TARGETS AFTER EXTENSIVE VISUAL CORTICAL ABLATIONS IN CATS

Impairments in reaching toward stationary and moving targets were stud ied in cats after restricted or extensive removal of visual cortical a reas (areas 17, 18 and 19 and lateral suprasylvian visual areas). Rega rdless of the extent of the cortical lesion, cats were at first unable to localise and reach for a stationary target whereas they were soon able to detect and accurately point toward a mobile one. Moreover, the onset latency of such movements was dramatically increased. During po st-operative re-training, the cats were unable to improve their accura cy scores when reaching towards stationary targets. In contrast, full compensation was observed for the accuracy of reaching movements direc ted toward moving targets. A partial recovery was observed for movemen t latency values that progressively decreased but left a permanent 30- 40 ms impairment following extensive lesions. The role of extragenicul ate messages and alternative routes involving other cortical areas in taking in charge the visuomotor activity is discussed.