Abstract
AbstractSpindle waves occur during the early stage of slow wave sleep and are thought to arise in the thalamic reticular nucleus (TRN), causing inhibitory postsynaptic potential spindle-like oscillations in the dorsal thalamus that are propagated to the cortex. We have found that thalamocortical neurons exhibit membrane oscillations that have spindle frequencies, consist of excitatory postsynaptic potentials, and co-occur with electroencephalographic spindles. TRN lesioning prolonged oscillations in the medial geniculate body (MGB) and auditory cortex (AC). Injection of GABA~A~ antagonist into the MGB decreased oscillation frequency, while injection of GABA~B~ antagonist increased spindle oscillations in the MGB and cortex. Thus, spindles originate in the dorsal thalamus and TRN inhibitory inputs modulate this process, with fast inhibition facilitating the internal frequency and slow inhibition limiting spindle occurrence.
Highlights
Spindle oscillations occur during the early stage of slow wave sleep and switch the thalamus from its relay function to OFF mode, partially isolating the cortex from sensory inputs and "calming" it
Previous intracellular recordings, performed mainly in deafferented brains, have shown that spindle oscillations in thalamocortical neurons are initiated by a series of inhibitory postsynaptic potential (IPSPs) that are associated with excitatory postsynaptic potentials (EPSPs) in the TRN5,10
The IPSP oscillation was not correlated with the EEG spindle in terms of co-occurrence, and occurrence frequency and duration, while the majority of neurons (26/42) showed spindles that started with and consisted of EPSPs in the medial geniculate body (MGB) with similar occurrence frequency and duration of the oscillation to those of the EEG spindle oscillation
Summary
Spindle oscillations occur during the early stage of slow wave sleep and switch the thalamus from its relay function to OFF mode, partially isolating the cortex from sensory inputs and "calming" it. Twenty-six MGB neurons showed EPSP membrane oscillations that coexisted with EEG spindles recorded in the cortex.
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