Subcortical Afferent Pathway Mediation of Extrastriate Cortex Function
There are two dominant pathways for visual signals to reach extrastriate visual cortex: 1) via the lateral geniculate nucleus (LGN) and primary visual cortex; and 2) via the midbrain (superior colliculus) and extrageniculate thalamus. We are presently examining the relative contributions that these two pathways make to functions mediated by extrastriate cortex. We have begun these studies by examining the contribution of the collicular pathway. In order to examine these contributions, bilateral pairs of cooling loops are implanted over the dorsal surface of the superior colliculus in order to permit their temporary deactivation. We are examining the contributions of the superior colliculus to the perception and cognition of space, discrimination of the direction and velocity of movement, figure/ground separation, local/global feature processing, and the learning and recall of objects and patterns. In the future, experiments will examine the behavioural contributions of the geniculate pathway. Other directions include an optical imaging assessment of neural changes in cortex during reversible deactivation of the superior colliculus.