Motor Skill and the Motor Cortex.

University Of Pittsburgh At Pittsburgh, Pittsburgh PA

Investigators

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Abstract

PROJECT SUMMARY The ability to perform a sequence of movements is a key component of motor skills (e.g., typing, playing a musical instrument, etc.). The preparation for and generation of sequential movements is generally thought to depend on premotor areas in the frontal lobe such as the supplementary motor area (SMA) and the pre-SMA (Roland et al., 1980; Tanji and Shima, '94; Gerloff et al., '97; Shima and Tanji, '98; Nakamura et al., '98; Picard and Strick, '01; Hikosaka et al., '02). According to this view, the primary motor cortex (M1) is thought to produce the patterns of muscle activity that are necessary to implement the plans generated by the premotor areas. There is growing evidence, however, that M1 is involved in both the acquisition and the retention of sequential movements (Matsuzaka et al., '07; Dayan and Cohen, '11; Picard et al., '13; see also Preliminary Results). These results have led us to propose that M1 is a site of storage for skilled movements. This application is designed to explore and test this hypothesis. A lesion of M1 will abolish the motor commands to the spinal cord that generate specific patterns of muscle activity. Instead, we propose to manipulate the protein synthesis and the regulation of gene expression in M1 of monkeys to selectively disrupt information storage in this cortical area. This approach has been successful in the experimental dissection and analysis of other memory systems in rodents (e.g., Nader et.al., `00; Kleim et al., '03; Miller et al., '10; Jarome et.al., `14). We will examine whether this manipulation in M1 of non-human primate disrupts the performance of sequential movements guided from memory without affecting the performance of movements guided by vision. We will train monkeys on two sequence tasks (Matsuzaka et al., `07). In one task, sequential movements are instructed by visual cues, whereas in the other task movements are internally generated from memory. After an animal becomes skilled in these tasks, we will inject inhibitors for protein synthesis and DNA methylation into M1 and test the monkey's performance of the tasks. In our preliminary experiments, injection of a protein synthesis inhibitor (anisomycin) into M1 successfully disrupted the performance of sequential movements guided from memory but did not have a significant effect on the performance of visually guided reaching, neural activity during visually guided reaching or hand trajectory of correct trials. On the other hand, inactivation of M1 using muscimol disrupted the performance of both tasks. We will acquire data using anisomycin from additional animals and data using other pharmacological agents (e.g. cycloheximide and inhibitor of DNA methylation) to explore and test our hypotheses. The proposed studies will provide some novel information on the cortical mechanisms that underlie a critical aspect of human behavior? the retention of motor skills.