Effects of sensory feedback on variations of intertap interval and force in finger-tapping sequences

This study was designed to examine effects of somatosensory feedback on var iations of intertrap interval and muscle force in finger-tapping sequences over 10 minutes. Although intertap intervals were decreased on the massed t ask as the time passed, the intervals were constant in the distributed task . In finger-tapping for a long time, impulses perhaps circulate within the loop circuits between the cerebral motor cortex and the peripheral nerve an d subsequently increase further the excitability of the circuits. This incr ease in the excitability within the circuits may shorten the interval and i ncrease variation oi the interval. On the other hand, although peak force i ncreased up to the 5-min. mark on the massed task, thr force decreased afte r the 6-min. mark. This increase of force also may be produced by increasin g activation of the corticoperipheral loop circuits. Although the decrease of force was perhaps produced by the fatigue of finger muscles for tapping during a few minutes, fatigue appeared more clearly in muscle force than in timing control. However, the force and the variation were constant in rile distributed task.