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Neural Plasticity
Volume 2009, Article ID 294192, 15 pages
Research Article

Plasticity of Horizontal Connections at a Functional Border in Adult Rat Somatosensory Cortex

1Laboratory of Neurobiology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
2Departments of Psychology and Interdepartmental Neuroscience Program, University of California, Riverside CA 92521-0426, USA

Received 13 August 2009; Revised 30 October 2009; Accepted 23 November 2009

Academic Editor: Małgorzata Kossut

Copyright © 2009 Sally A. Marik and Peter W. Hickmott. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Horizontal connections in superficial cortical layers integrate information across sensory maps by connecting related functional columns. It has been hypothesized that these connections mediate cortical reorganization via synaptic plasticity. However, it is not known if the horizontal connections from discontinuous cortical regions can undergo plasticity in the adult. Here we located the border between two discontinuous cortical representations in vivo and used either pairing or low-frequency stimulation to induce synaptic plasticity in the horizontal connections surrounding this border in vitro. Individual neurons revealed significant and diverse forms of synaptic plasticity for horizontal connections within a continuous representation and discontinuous representations. Interestingly, both enhancement and depression were observed following both plasticity paradigms. Furthermore, plasticity was not restricted by the border's presence. Depolarization in the absence of synaptic stimulation also produced synaptic plasticity, but with different characteristics. These experiments suggest that plasticity of horizontal connections may mediate functional reorganization.