Speeded manual responses to unseen visual stimuli in hemianopic patients: what kind of blindsight?

ABSTRACT

Blindsight, i.e., unconscious visually guided behaviour triggered by stimuli presented to a cortically blind hemifield, has been typically found either by using direct (forced choice) or indirect (interhemispheric) methods. However, one would expect to find blindsight also in fast responses to suddenly appearing visual stimuli, a reminiscence of evolutionary ancient adaptive behaviour. In this study we provide preliminary evidence of this form of blindsight by using a conservative method for assessing blindsight based on a comparison between the cumulative probability functions (CPFs) of simple reaction times to blind and intact field stimuli. Furthermore, in two patients with blindsight we provided evidence that their above-chance unconscious responses were likely to be triggered by the intact hemisphere.