II Sensory Feedback Influences on Keytapping Motor Tasks

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Abstract
Subjects were trained to tap a key continuously at a specific rate, and with a specific amount of pressure (regularity task). Performance of this task was studied under conditions of: (a) decreased auditory feedback (masking noise through earphones), (b) decreased visual feedback (tapping hand screened from view), (c) vibration (vibrators applied to forearm in order to “mask” proprioceptive feedback), (d) digital block of tapping finger, and (e) combination of all four conditions. Significant changes in rate and intensity of tapping resulted under conditions of decreased auditory feedback, vibration, and the combined condition. In the second part of the study, the effects of different delayed sensory events on keytapping were examined. The five conditions of delayed sensory feedback were: (a) delayed auditory feedback, (b) delayed visual feedback, (c) delayed tactile feedback, (d) the first three delayed sensory events presented simultaneously, and (e) condition (d) repeated with digital block of the tapping finger. The conditions of delayed sensory feedback did not markedly alter performance of the regularity task. The same conditions of delayed sensory feedback did, however, produce highly significant changes in the performance of a more complex pattern task. All of these delay conditions produced parallel changes in the pattern task, namely increased intensity and decreased rate of tapping. The fact that the pattern task is more disturbed by delayed sensory feedback than the regularity task suggests that temporal complexity of the task is one determinant of the degree to which it will be disturbed by a delay in sensory feedback.