Walsh & Hoyt: Explanations of Blindsight

Once these objections are met, one can turn to consideration of the anatomic origins of blindsight. The most common explanation invokes alternative visual pathways. A purely subcortical pathway from retina to superior colliculus may explain a function like spatial localization. It is claimed that better blindsight in the temporal than nasal hemifield of patients is a signature of collicular mediation. Other functions like pattern or motion detection may require extrastriate cortex, through a relay involving the superior colliculus and pulvinar. Since the colliculus lacks responses to color opponency, chromatic blindsight may indicate yet another relay, perhaps direct projections to extrastriate cortex from surviving lateral geniculate neurons.