Massimo Scanziani, University of California, San Francisco

A Cortical Visual Area for the Processing of Collicular Information

Two distinct anatomical pathways carry visual signals from the retina to visual cortex. One pathway, the geniculo-striate pathway, passes through the dorsolateral geniculate nucleus of the thalamus to innervate primary visual cortex (V1). V1, in turn, sends axonal projections to higher visual areas (HVAs), visually responsive and retinotopically organized cortical regions surrounding V1. The other route, the collicular pathway, passes through the superior colliculus (SC) and reaches HVA via the pulvinar nucleus of the thalamus. While much is known about the role the geniculo-striate pathway plays in the cortical response to visual stimuli, the role of the collicular pathway is not well understood. I will show that visual responses in mouse postrhinal cortex (POR), an HVA and gateway for visual input to the hippocampal formation, are abolished upon silencing the SC. By contrast, silencing V1 has a minor impact on visual responses in POR. Furthermore, I will show that the SC connects to POR through a disynaptic input via a region of the pulvinar that is insensitive to V1 activity. Finally, I will show that POR neurons greatly outperform V1 neurons at discriminating small objects moving along a linear trajectory. The ability of POR to extract stimulus features poorly discriminated by V1 indicates that the two visual pathways to the cortex capture different aspects of the visual world. Since the collicular pathway is considered phylogenetically older than the geniculo-striate pathway, and given the functional dependence of POR on SC, POR may be considered an ancestral sensory visual area specialized in the processing of collicular information.

Organized by

Henning Sprekeler/Margret Franke

Location

BCCN Berlin, lecture hall, Philippstr. 13 Haus 6, 10115 Berlin