Murray Sherman, PhD

Professor
Department of Neurobiology, Pharmacology, and Physiology
University of Chicago
Chicago, Illinois
November 20, 2006

The Role of the Thalamus: Relay Functions and More

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. First- and higher-order thalamic relays can also be recognized for the somatosensory and auditory thalamic systems, and this division of thalamic relays can also be extended beyond sensory systems. Thus the first- and higher-order thalamic equivalents of the somatosensory and auditory systems are, respectively, the ventral posterior nucleus and the posterior medial nucleus (somatosensory), and the ventral (versus dorsal) portion of the medial geniculate nucleus (auditory). Other thalamic nuclei have also been placed into this framework, and so the medial dorsal nucleus is mostly higher-order, while the ventral anterior and ventral lateral nuclei seem to be a mosaic of the first- and higher-order relays. It now seems clear that most of the thalamus is composed of higher-order relays.

Higher-order relays seem especially important to general corticocortical communication, and this view challenges and extends the conventional view that such communication is based mainly 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. Thus the thalamus is not just a simple relay responsible for getting peripheral information to the cortex. Instead, it provides a behaviorally relevant, dynamic control over the nature of information relayed, and it also plays a key role in basic corticocortical communication.

 

 

 

Speaker Schedule  |  Reports from Previous Years
Top of Page | Life Sciences | Brandeis University