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THE INFLUENCE OF CONSCIOUS CONTROL OF MOVEMENT ON BRAIN PROCESSES AND THE QUALITY OF COGNITIVE-MOTOR PERFORMANCE
Hatfield, Bradley D.
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The impact of mental stress on fine motor performance is typically maladaptive. The current research was conducted to investigate the manner by which state anxiety affects performance using a cognitive neuroscience perspective. The basic proposition tested, derived from the Reinvestment Theory and the Psychomotor Efficiency Hypothesis, is that stress introduces neuromotor noise to motor planning processes that translate as excess recruitment of motor units and degrade performance. Electroencephalography (EEG) was employed in Study 1 to assess regional cortical activation and cortico-cortical communication between non-motor associative and motor planning regions during the preparatory period of a dart-throwing task. The task was performed during stress (i.e., social evaluation, monetary incentives, and threat of electrical shock) and a relatively relaxed control condition through a within-subjects design. Regional activation was estimated from bilateral EEG recordings in the frontal, central, temporal, parietal, and occipital regions via spectral analysis to assess low-alpha and high-alpha band power to determine generalized arousal and task-relevant attentional focus, respectively. Cortico-cortical communication was estimated between all bilateral regions and the frontal motor planning area with particular emphasis on the left temporal (T3) to midline frontal (Fz) coherence. Elevated state anxiety was induced and associated with heightened T3-Fz EEG connectivity and synchrony of high-alpha band in the right occipital region. Based on these findings, Study 2 was conducted to determine the psychological processes accounting for the observed elevation in T3-Fz EEG coherence and the quality of muscle action during the throwing task. Specifically, participants employed an internal and an external attentional focus to perform the throwing task while their EEG and electromyography (EMG) were monitored. The use of internal focus, which is consistent with explicit monitoring of movement mechanics, was predicted to result in elevated T3-Fz EEG connectivity. This prediction was supported and, furthermore, the magnitude of connectivity was positively associated with motor unit activity assessed via EMG of four major muscle groups (i.e., flexor carpi ulnaris, extensor carpi radialis, biceps brachii, and triceps brachii). The evidence provided supports the theoretical notion that explicit monitoring promotes inefficient muscle activity, which mediates to impact performance negatively.