Lesion of primary visual cortex in monkey impairs the inhibitory but not the facilitatory cueing effect on saccade.

Prior visual stimulus presentation induces immediate facilitation and subsequent inhibition of orienting to an ensuing target at the same location. Recent studies revealed that the superior colliculus (SC) is involved in these facilitatory and inhibitory cueing effects on saccade; however, as the SC receives inputs both directly from the retina (retino-tectal pathway) and indirectly from visual cortices (geniculostriate pathway), it is unclear which visual pathway contributes to the effects. We investigated this issue using monkeys with lesions in the primary visual cortex (V1), thus depriving the SC of the geniculostriate pathway and leaving the retino-tectal pathway intact. We found that the inhibitory cueing effect was selectively impaired and the facilitatory cueing effect was spared after V1 lesions. The results suggest that the geniculostriate and the retino-tectal pathways are differentially involved in the generation of cueing effects on saccade: The former is critically involved in the inhibitory effect whereas the latter alone can induce the facilitatory effect. The results provide the first direct evidence for the involvement of the geniculostriate pathway in the inhibitory cueing effect and further imply that the more recent evolution of the geniculostriate pathway in higher mammals improves the efficiency of visual search by inhibiting orienting to a previously attended location.