The oculomotor distractor effect in normal and hemianopic vision

The present study investigated the inhibitory effect of visual distracters on the latency of saccades made by hemianopic and normal human subjects. The latency of saccades made by hemianopic subjects to stimuli in their intact visual field was not affected by visual distracters presented within their hemianopic field. In contrast, the latency of saccades made by normal subjects was increased significantly under distracter conditions. The latency increase was larger for temporal than nasal distracters. The results are inconsistent with previous proposals that the crossed retinotectal pathway from the nasal hemiretina to the superior colliculus may mediate a blindsight inhibitory effect when distracters appear within a hemianopic temporal visual field. Instead, the distracter effect appears to reflect the normal processes involved in saccade target selection which may be mediated by a circuit involving both cortical and subcortical structures.