Saccade control after V1 lesion revisited.

A number of previous articles on blindsight have stressed that even after the lesion of the primary visual cortex (V1), subjects can perform visually guided saccades toward the targets in the blind field and that the extrageniculate visual pathway which bypasses the V1 can control the saccades by itself. However, in monkey model of V1 lesion, about two months of time is needed for recovery, suggesting that the extrageniculate visual pathway cannot immediately take over the function of the geniculo-striatal pathway, and on close look at the dynamics of saccades, saccades became ballistic and online corrections of trajectories and velocities were impaired, and that decision threshold for saccade initiation was lowered. On the basis of these findings, we propose that the visual signal through V1 is necessary for deliberate control of saccades.