Redwood Neuroscience
Title "The Role of Thalamus in the
Flow of Information to Cortex”
Neurobiology,
Pharmacology and Physiology,
The
Abstract:
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 new observations that have dramatically changed
this view. First, ~95% of input to LGN relay cells 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 calcium conductance that determines response
properties of relay cells and thus affects the very nature of information
relayed. Second, the LGN and pulvinar (a massive but
generally mysterious and ignored thalamic relay), are examples of two different
types of relay: the LGN 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 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.