NEW YORK (Reuters Health) – Neuronal activity in the medial temporal lobe (MTL) diminishes just before cognitive lapses in individuals who are sleep deprived, researchers report.
Sleep deprivation is associated with impaired behavioral performance during wakefulness, and these cognitive lapses have recently been associated with EEG changes.
Dr. Yuval Nir from Tel Aviv University, in Israel, and colleagues used intracranial electrodes to record single-neuron activities and local field potentials in two human neurosurgical patients performing a psychomotor vigilance task over several experimental sessions, including a session after full-night sleep deprivation.
Cognitive lapses (defined as delayed, not absent, behavioral responses) followed sleep deprivation in these patients, and time spent awake (TSA) before each experimental session significantly predicted slow performance.
In contrast, however, accuracy of performance was not affected by TSA, the researchers report in Nature Medicine, online November 6.
Visual stimuli used in the psychomotor vigilance task elicited robust neuronal responses, especially in the MTL, and cognitive lapses were associated with weaker and delayed neuronal spiking discharges relative to responses during faster performance.
Delays in MTL responsiveness were associated with a selectively weakened decrease in slow/theta power in EEG channels even before cognitive lapses manifested.
“Thus, degraded neuronal activity is already evident at the perceptual stage, in which responses of individual neurons in selected trials can predict subsequent cognitive lapses,” the researchers conclude. “The extent to which these effects are regionally specific remains unclear, but the current results establish that, within MTL regions, cognitive lapses specifically affect responsive circuits engaged in the task.”
“The tight relationship between MTL activity and perception suggests that visual recognition itself may slow down as a result of sleep deprivation,” they note. “The mechanisms underlying local neuronal lapses remain to be determined, although it is likely that transient instability in the activity of neuromodulatory systems, including cholinergic and noradrenergic neurons, may play a role.”
Dr. Mathias Basner from the University of Pennsylvania Perelman School of Medicine’s division of sleep and chronobiology in psychiatry, in Philadelphia, told Reuters Health by email, “The findings provide a neurobiological basis for the phenomenon of sporadically occurring lapses or micro-sleeps, with the long-term potential of identifying drugs that could counteract the identified mechanisms.”
“Acute and chronic sleep loss degrade cognitive performance and, if they exceed relevant levels, pose a threat to patient and physician safety,” he said. “Seven hours of sleep daily on a chronic basis are a prerequisite for optimal performance and health.”
Dr. Nir and colleagues did not respond to a request for comment.
SOURCE: http://bit.ly/2zkpChs
Nat Med 2017.
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