Abstract
Visual stimulus first captures attention thus facilitates subsequent reaction to that location but then the reaction is inhibited. The former facilitatory effect is termed attention capture, while the latter inhibitory effect is termed inhibition of return (IOR). These effects can be measured by the change of the saccadic reaction time (SRT) in the oculomotor psychophysical task. SRT to the saccadic target is changed by the preceding cue stimulus presented at the same location: SRT is shortened if the time interval between cue and target is short (100–200ms), while SRT is prolonged if the interval is longer (e.g. [[gt]] 300ms). Recent works revealed that the superior colliculus (SC), known as a center of orienting response, is important for IOR. However, SC receives visual information from several regions such as visual cortex, frontal cortex including frontal eye field (FEF) and retina. So it is still unclear which visual information is essential for IOR. To address this question, we made a lesion in unilateral primary visual cortex (V1) in the macaque monkey and measured the SRT using visually guided saccade task with a cue stimulus described above. The cue stimulus was randomly presented either in the same or the different location to the saccadic target. We have found that the IOR effect remains if the saccadic target is presented in the ipsilateral visual field to the lesion but disappears if the saccadic target is presented contralaterally to the lesion, indicating that the striatal visual pathway is essential for IOR. However, the attention capture is still observed in the impaired visual field which suggests the involvement of the retino-collicular visual pathway in this effect. Thus, the attention capture and IOR might be mediated by the different neural systems in the brain.