Slide 33

Summary: Thalamocortical Relations in Sleep, Waking and Epilespy

Our results reveal that single thalamic neurons exhibit two distinct states of activity: rhythmic burst firing during slow wave sleep and tonic firing during waking. The interactions of the intrinsic membrane properties of thalamic neurons with other thalamic and cortical cells results in the generation of complex patterns of synchronized oscillations such as spindle waves.

Some types of epileptic seizures, such as Absence seizures, appear to result from a perversion of normal synchronized oscillations. Our results further support that hypothesis the Absence seizures are a bizarre form of spindle waves.

Finally, synchronized oscillations disappear in the transition from sleep to waking owing to the depolarization of thalamocortical and thalamic reticular neurons. This depolarization results from the release of a number of different neurotransmitters including acetylcholine, norepinephrine, histamine, serotonin, and glutamate.

By depolarizing thalamic neurons, these modulatory neurotransmitter systems abolish the generation of sleep rhythms and move the forebrain into a state that is conducive to the processing of sensory information.

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