Abstract
The pulvinar has long been recognized as a way station on a second visual pathway to the cerebral cortex. This identification has largely been based on the pulvinar’s connections, which are appropriate for providing visual information to multiple regions of visual cortex from subcortical areas. What is little known is what information pulvinar actually conveys especially in the intact functioning visual system. We have identified one pathway through the pulvinar that extends from superior colliculus superficial visual layers though inferior pulvinar (principally PIm) to cortical area MT by using the techniques of combined anti- and orthodromic stimulation. We now have explored what this pathway might convey to cortex and have first concentrated on a modulation of visual processing first seen in SC, the suppression of visual responses during saccades. We have been able to replicate the previous observations of the suppression in SC and in MT and now show that PIm neurons also are similarly suppressed. We have then inactivated SC and shown that the suppression in MT is reduced. While we do not know all of the signals conveyed through this pathway to cortex, we do have evidence for one: the suppression of vision during saccades. This signal is neither a visual nor a motor signal but conveys the action of an internal motor signal on visual processing. Furthermore combining our results in the behaving monkey with recent experiments in mouse brain slices (Phongphanphanee et al. 2011) provides a complete circuit from brainstem to cortex for conveying this suppression.
Meeting abstract presented at VSS 2012