Synchrony between single neurons in the human brain during sleep

Richard J. Staba, Gabriel Kreiman, Charles L.. Wilson and Itzhak Fried

Annual Meeting of the Society for Neuroscience, San Diego, 2001

In order to study the neuronal mechanisms occurring during sleep we directly compared the spontaneous electrophysiological activity of ensembles of single neurons in the human temporal and frontal lobes while subjects were awake, during slow wave sleep (SWS) and during rapid eye movement (REM) sleep. Subjects were patients with pharmacologically intractable epilepsy who were implanted with depth electrodes to localize the seizure focus for possible surgical resection. The number of electrodes as well as their position was based exclusively on clinical criteria. Electroencephalographic (EEG), electro-oculogram (EOG) and chin electro-myogram (EMG) activity were concurrently monitored and used to classify the different sleep stages. We recorded from a total of 141 neurons mostly located in the hippocampus and entorhinal cortex. We observed a significant increase in the number and strength of synchronous discharge among pairs and triplets of neurons during slow wave sleep compared to the other two states. The proportion of pairs of neurons that showed significant synchronous firing was 11.3%, 20.9% and 8.0% during wake, SWS and REM sleep states respectively. For triplets, the proportions were 2.0%, 8.4% and 3.1% respectively. Such synchronous activity could provide an important physiological mechanism for the transfer of information from the hippocampus to neocortex and the modification of neuronal synaptic strength during sleep. Supported by NSF-ERC and NINDS