During slow wave sleep the main activity of cortical neurons consists of synchronous and rhythmic alternations of the membrane potential between depolarized and hyperpolarized values. The latter are long-lasting (200-600 ms) periods of silence. The mechanisms responsible for this periodical interruption of cortical network activity are unknown. Here we report a decrease of ∼20% in the extracellular calcium concentration ([Ca]out) progressively taking place in the cortex between the onset and the offset of the depolarizing phase of the slow sleep oscillation. Since [Ca]out exerts a high gain modulation of synaptic transmission, we estimated the associated transmitter release probability and found a corresponding 50% drop. Thus the periods of silence occurring in the cortical network during slow wave sleep are promoted by recurrent [Ca]out depletions.
|Number of pages||5|
|Journal||Journal of Neurophysiology|
|Publication status||Published - 2001|
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