Sherman Lab

Traditionally, this laboratory has investigated aspects of vision, using animal models with anatomical, physiological, pharmacological, and behavioral approaches to reveal neural substrates of processing in the central visual pathways. More recently, the work has focused in thalamus and thalamocortical interactions, and it has extended from the visual system into other aspects of thalamocortical interactions, such as those in the somatosensory pathways.

The thalamus has long had a bad press, seen as a simple, machine-like relay of information to cortex. Work on the visual thalamic relays provides two key properties that have dramatically changed this view. First, ~95% of input to relay cells of the lateral geniculate nucleus (the thalamic relay to cortex of retinal input) is nonretinal and modulates the relay in dynamic and important ways related to behavioral state, including attention. Much of this is related to control of a voltage-gated, low threshold Ca2+ conductance that determines response properties of relay cells and thus affects the very nature of information relayed. Second, the lateral geniculate nucleus and pulvinar (a massive but generally mysterious and ignored thalamic relay that provides input to the many extrastriate visual areas of cortex), are examples of two different types of relay: the lateral geniculate nucleus is a first order relay, transmitting information from a subcortical source (retina), while the pulvinar is mostly a higher order relay, transmitting information from layer 5 of one cortical area to another area. Higher order relays seem especially important to general corticocortical communication, and this view challenges the conventional dogma that such communication is based on direct corticocortical connections. In this sense, any new information reaching a cortical area, whether from a subcortical source or another cortical area, benefits from a thalamic relay. Other examples of first order and higher order relays also exist. Thus the thalamus not only provides a behaviorally relevant, dynamic control over the nature of information relayed, it also plays a key role in basic corticocortical communication.