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Neocortical activation of the hippocampus during sleep in infant rats
Journal article   Open access   Peer reviewed

Neocortical activation of the hippocampus during sleep in infant rats

Ethan J Mohns and Mark S Blumberg
The Journal of neuroscience, Vol.30(9), pp.3438-3449
03/03/2010
DOI: 10.1523/jneurosci.4832-09.2010
PMCID: PMC2851014
PMID: 20203203
url
https://doi.org/10.1523/jneurosci.4832-09.2010View
Published (Version of record) Open Access

Abstract

We recently reported that the majority of hippocampal neurons in newborn rats increase their activity in association with myoclonic twitches, which are indicative of active sleep. Because spindle bursts in the developing somatosensory neocortex occur in response to sensory feedback from myoclonic twitching, we hypothesized that the state-dependent activity of the newborn hippocampus arises from sensory feedback that sequentially activates the neocortex and then hippocampus, constituting an early form of neocortical-hippocampal communication. Here, in unanesthetized 5- to 6-d-old rats, we test this hypothesis by recording simultaneously from forelimb and barrel regions of somatosensory neocortex and dorsal hippocampus during periods of spontaneous sleep and wakefulness and in response to peripheral stimulation. Myoclonic twitches were consistently followed by neocortical spindle bursts, which were in turn consistently followed by bursts of hippocampal unit activity; moreover, spindle burst power was positively correlated with hippocampal unit activity. In addition, exogenous stimulation consistently evoked this neocortical-to-hippocampal sequence of activation. Finally, parahippocampal lesions that disrupted functional connections between the neocortex and hippocampus effectively disrupted the transmission of both spontaneous and evoked neocortical activity to the hippocampus. These findings suggest that sleep-related motor activity contributes to the development of neocortical and hippocampal circuits and provides a foundation on which coordinated activity between these two forebrain structures develops.
Animals, Newborn Feedback, Sensory - physiology Neocortex - anatomy & histology Muscle, Skeletal - growth & development Somatosensory Cortex - growth & development Neural Pathways - growth & development Neocortex - growth & development Rats Evoked Potentials - physiology Male Muscle, Skeletal - innervation Rats, Sprague-Dawley Somatosensory Cortex - anatomy & histology Action Potentials - physiology Neural Pathways - anatomy & histology Animals Aging - physiology Muscle Contraction - physiology Neurons - physiology Wakefulness - physiology Female Hippocampus - anatomy & histology Sleep - physiology Hippocampus - growth & development

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