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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. |
