Different modulation of common motor information in rat primary and secondary motor cortices
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Saiki, Akiko 大学院医歯薬保健学研究科（医）
Rodents have primary and secondary motor cortices that are involved in the execution of voluntary movements via their direct and parallel projections to the spinal cord. However, it is unclear whether the rodent secondary motor cortex has any motor function distinct from the primary motor cortex to properly control voluntary movements. In the present study, we quantitatively examined neuronal activity in the caudal forelimb area (CFA) of the primary motor cortex and rostral forelimb area (RFA) of the secondary motor cortex in head-fixed rats performing forelimb movements (pushing, holding, and pulling a lever). We found virtually no major differences between CFA and RFA neurons, regardless of neuron subtypes, not only in their basal spiking properties but also in the time-course, amplitude, and direction preference of their functional activation for simple forelimb movements. However, the RFA neurons, as compared with the CFA neurons, showed obviously a greater susceptibility of their functional activation to an alteration in a behavioral situation, a 'rewarding' response that leads to reward or a 'consummatory' response that follows reward water, which might be accompanied by some internal adaptations without affecting the motor outputs. Our results suggest that, although the CFA and RFA neurons commonly process fundamental motor information to properly control forelimb movements, the RFA neurons may be functionally differentiated to integrate motor information with internal state information for an adaptation to goal-directed behaviors.
This work was supported by JST CREST (Y.I.), Grants-in-Aid for Scientific Research on Innovative Areas (Y.I., 22120520, 24120715) and for Scientific Research (B) (Y.I., 24300143) from MEXT, and research grants from the Uehara Memorial Foundation (Y.I.) and Brain Science Foundation (Y.I.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Public Library of Science
© 2014 Saiki et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.