The Development of Complex Movement Motor Maps Using Long Duration Intracortical Microstimulation (LD-ICMS) in Rats
Date
2014-09-29
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Abstract
The adult motor cortex is topographically organized into representations (maps) of different body parts (Fritsch & Hitzig, 1870; Ferrier, 1873). Recent evidence, however suggests a movement-based, rather than, muscle-based cortical motor organization (Graziano et al., 2002; Brown & Teskey, in press). In the adult rat, four specialized multi-joint forelimb movements have been consistently evoked using long-duration intracortical microstimulation (LD-ICMS; limb elevation, advancement, grasping, and retraction) that are thought to recapitulate components of the basic walking and reaching movements in rats (Karl & Whishaw, 2013; Brown and Teskey, in press). The present experiment characterized the behavioural and cortical development of these four movement categories in Long-Evans hooded rats and how skilled reach training could affect forelimb development. This study was the first to find that LD-ICMS evoked single-joint movements developed before multi-joint movements within the neocortex. In addition, the forelimb behavioural capacity of the rat predated the emergence of LD-ICMS-evoked forelimb responses indicating that subcortical structures might be mediating behaviour. Moreover, this study revealed for the first time that grasp movements were not restricted to the “grasp region” at early stages of development, suggesting that the motor cortex underwent large cortical changes as the rat developed, leaving a refined grasp region in adulthood. Finally, after skilled reach training, the LD-ICMS motor map of the hemisphere contralateral to the skilled reach trained forelimb contained more grasp movements than the ipsilateral hemisphere, which is not observed in adult rats (Ramanathan et al., 2006; Brown & Teskey, in press). This novel finding revealed that rat motor maps might be more plastic throughout development than in adulthood. It is important to understand how forelimb movements develop within the cortex in order to begin finding solutions for when these areas become damaged, such as during a stroke.
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Neuroscience, Psychology--Behavioral, Psychology--Developmental
Citation
Singleton, A. (2014). The Development of Complex Movement Motor Maps Using Long Duration Intracortical Microstimulation (LD-ICMS) in Rats (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/28059