INTEGRATION OF INTRA-AUDITORY MODALITIES FOR THE ENHANCEMENT OF MOTOR PERFORMANCE AND COORDINATION IN A CONSTANT FORCE PRODUCTION TASK
Shim, Jae Kun
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One of most fundamental problems in the field of neuromechanics is to understand how the central nervous system (CNS) integrates multiple sources of sensory information and coordinates multiple effectors in human movement. Much attention has been directed to the integration of multiple modalities between sensory organs (e.g., visual and auditory, visual and tactile, or visual and proprioceptor), while little is known about the integration of multiple modalities within one sensory (i.e., intra-sensory integration), especially regarding the auditory sensory. This dissertation investigated the mechanisms of intra-auditory integration for the control of multiple fingers during constant force production tasks, specifically regarding how the CNS utilizes multiple sources in auditory feedback, how the CNS deals with uncertainty in auditory feedback, and how the CNS adapts or learns a motor task using auditory feedback. The specific aims of this dissertation included: 1) development of analytical tools for the quantification of motor performance and coordination in a hierarchical structure of motor variability; 2) investigation into the effect of intra-auditory integration on motor performance and coordination (Experiment I); 3) investigation of the role of uncertainty in auditory information on the effectiveness of intra-auditory integration in motor performance and coordination (Experiment II); and 4) investigation of the auditory-motor learning in the context of motor performance and coordination (Experiment III). Results from Experiments I & II have indicated that the CNS can integrate frequency and intensity of auditory information to enhance motor performance and coordination among fingers. Intra-auditory integration was found to be most effective when uncertainty in auditory feedback was moderate between two extreme levels of uncertainty (low and high uncertainty). Results from Experiment III indicate that practice leads to the enhancement of performance by reducing individual finger variability without changes in inter-finger coordination. Further, the enhancement of performance and coordination after practice was specific to the intra-auditory modality that was available during practice. This dissertation discusses the mechanisms responsible for the changes in motor performance and coordination with auditory feedback and directions for future research are suggested.