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Cereb Cortex. 2013 Sep;23(9):2225-34. doi: 10.1093/cercor/bhs209. Epub 2012 Jul 17.

Activation patterns in superficial layers of neocortex change between experiences independent of behavior, environment, or the hippocampus.

Author information

1
Arizona Research Laboratories Division of Neural Systems, Memory, and Aging, University of Arizona, Tucson, AZ 85724-5115, USA.

Abstract

Previous work suggests that activation patterns of neurons in superficial layers of the neocortex are more sensitive to spatial context than activation patterns in deep cortical layers. A possible source of this laminar difference is the distribution of contextual information to the superficial cortical layers carried by hippocampal efferents that travel through the entorhinal cortex and subiculum. To evaluate the role that the hippocampus plays in determining context sensitivity in superficial cortical layers, behavior-induced expression of the immediate early gene Arc was examined in hippocampus-lesioned and control rats after exposing them to 2 distinct contexts. Contrary to expectations, hippocampal lesions had no observable effect on Arc expression in any neocortical layer relative to controls. Furthermore, another group of intact animals was exposed to the same environment twice, to determine the reliability of Arc-expression patterns across identical contextual and behavioral episodes. Although this condition included no difference in external input between 2 epochs, the significant layer differences in Arc expression still remained. Thus, laminar differences in activation or plasticity patterns are not likely to arise from hippocampal sources or differences in external inputs, but are more likely to be an intrinsic property of the neocortex.

KEYWORDS:

context; episodic memory; hippocampus; immediate early gene; neocortex

PMID:
22806267
PMCID:
PMC3733063
DOI:
10.1093/cercor/bhs209
[Indexed for MEDLINE]
Free PMC Article

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