The role of T-channels in the generation of thalamocortical rhythms.

The presence of T-channels in thalamic cells allows for the generation of rhythmic bursts of spikes and the existence of two firing modes in thalamic cells: tonic and bursting. This intrinsic electrophysiological property has fundamental consequences for the functional properties of the thalamus across waking and sleep stages and is centrally implicated in a growing number of pathological states. Rhythmic bursting brings about highly synchronized activity throughout corticothalamic circuits which is incompatible with the relay of information through the thalamus. Understanding the conditions that determine the change in firing mode of thalamic cells as well as the role of bursting in the generation of synchronized oscillations is critical to understand the function of the thalamus. The functional properties of T-channels and the resulting low threshold spike are discussed here with emphasis on the differences in the bursting properties of reticular thalamic and thalamocortical neurons. The role of thalamic bursting in the generation of sleep oscillations and their specific sequence during slow wave sleep will also be discussed.