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 (geniculo-striate 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 geniculo-striate 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 geniculo-striate 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 geniculo-striate pathway in the inhibitory cueing effect, and further imply that the more recent evolution of the geniculo-striate pathway in higher mammals improves the efficiency of visual search by inhibiting orienting to a previously attended location.
Takuro Ikeda, Masatoshi Yoshida, and Tadashi Isa
National Institute for Physiological Sciences, Okazaki, Japan
Journal of Cognitive Neuroscience (Early Access)
(A) Schematic drawing of geniculo-striate and retino-tectal pathways. Solid arrows represent the retino-tectal pathway mediated by a direct retino-tectal projection. Dashed arrows represent the geniculo-striate pathway via primary visual cortex (V1) to the lateral intraparietal area (LIP), frontal eye field (FEF), supplementary eye field (SEP), and other related areas that would be impaired after a V1 lesion.
(B) Experimental design. Monkeys had to make correct saccades to the target to obtain juice reward. The two possible locations for the cue and the target were fixed in each block of 60-100 successful trials. SOA: stimulus onset asynchronies.
(C) Cueing effects on saccadic reaction time (SRT). Cueing effects on SRT was defined as the difference in mean SRTs between the two cue condition [SRT in different condition – SRT in same condition]. The effects were plotted against SOA between cue and target. Positive value indicates facilitatory effect and negative value indicates inhibitory effects. Significant inhibitory effects were observed in the normal field (blue line) whereas no inhibitory but significant facilitatory effects were observed after V1 lesion (red line), suggesting that the geniculo-striate pathway is critically involved in the inhibitory cueing effect.
