抄録
This study investigated the influence of inter-onset interval (IOI) shift from 1 to 20% of 1,500 ms on the control of reactive movements. Ten healthy individuals (8 males, 2 females; mean age, 25.5 ± 3.7 years) participated in this study. All subjects performed reaction time tasks, raising their right ankles in response to an auditory stimulus. There were 21 test conditions: periodic auditory stimuli at an IOI of 1,500 ms, and shifts in the IOI from 1 to 20% of 1,500 ms, in successive stimuli at an IOI of 1,500 ms. The electromyographic reaction times (EMG-RTs) were compared among EMG-RT responses to stimuli 6 to 10, EMG-RT responses to stimuli which shortened IOI, and EMG-RT responses to stimuli 1 to 5 which shortened IOI. EMG-RT responses to stimuli which shortened IOI were compared among the 21 conditions. Under each condition, the EMG-RT responses to stimulus 2 were significantly shortened compared to the response to stimulus 1 (p<0.01). Under conditions of periodic auditory stimuli at an IOI of 1,500 ms and a shift in the IOI from 1 to 7% of 1,500 ms, the EMG-RT responses after stimulus 3 were significantly shortened compared with stimulus 2 (p<0.01). Under conditions of shift in the IOI from 8 to 20% of 1,500 ms, the EMG-RT responses to stimuli which shortened IOI were significantly delayed compared with stimuli 3 to 5 (p<0.01). The EMG-RT responses after stimuli 1 to 5, which shortened IOI, were significantly shortened compared with stimuli which shortened IOI (p<0.01). For shifts in the IOI from 12 to 20% of 1,500 ms, EMG-RT responses to stimuli which shortened IOI and after stimuli 1 to 5, which shortened IOI, were significantly delayed compared with stimuli 3 to 5 (p<0.01). In the comparison of the 21 conditions, the EMG-RTs of shifts in IOI from 8 to 20% of 1,500 ms were significantly delayed compared with periodic auditory stimuli with an IOI of 1,500 ms, and shifts in IOI from 1 to 7% of 1,500 ms (p<0.01). Periodic rhythmic stimulation of 1,500 ms interval is predicted to comprise about 100 ms width, and reactive movements can be performed without delay under conditions with an IOI shift 7% of 1,500 ms.
