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Previous studies of fine motor control have focused on the ability of participants to match their grip force production to a visually provided template. We investigated differences exhibited in pinch force control during variable force production templates, including sine-, sawtooth-, and square-wave templates. Our results indicate that increased force requirements are associated with increased error rates and a noisier frequency spectrum, consistent with previous studies. Our results also indicate that visual feedback, in the form of template shape, directly affect pinch force production features and motor unit firing patterns, despite the use of consistent baseline force requirements, amplitude changes, and visual signal frequency. This suggests that CNS modulation of motor unit responses can be triggered by basic changes in visual feedback unrelated to force requirements. The potential implications of error compensation based on this study due to aging are also discussed.
The authors are with the Center for Neuromotor and Biomechanics Research, University of Houston, Houston, TX.