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This Article Full Text Full Text (PDF) All Versions of this Article: 93/3/1486    most recent 00958.2004v2 00958.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Cohen, J. D. Articles by Castro-Alamancos, M. A. Search for Related Content PubMed PubMed Citation Articles by Cohen, J. D. Articles by Castro-Alamancos, M. A.

Skilled Motor Learning Does Not Enhance Long-Term Depression in the Motor Cortex In Vivo

Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania

Submitted 15 September 2004; accepted in final form 21 October 2004

Learning of motor skills may occur as a consequence of changes in the efficacy of synaptic connections in the primary motor cortex. We investigated if learning in a reaching task affects the excitability, short-term plasticity, and long-term plasticity of horizontal connections in layers II–III of the motor cortex. Because training in this task requires animals to be food-deprived, we compared the trained animals with similarly food-deprived untrained animals and normal controls. The results show that the excitability, short-term plasticity, and long-term plasticity of the studied horizontal connections were unaffected by motor learning. However, stress-related effects produced by food deprivation and handling significantly enhanced the expression of long-term depression in these pathways. These results are compatible with the hypothesis that the acquisition of a complex motor skill produces bi-directional changes in synaptic strength that are distributed throughout the complex neural networks of motor cortex, which remains synaptically balanced during learning. The results are incompatible with the idea that learning causes large unidirectional changes in the population response of these neural networks, which may occur instead during certain behavioral states, such as stress.

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