抄録
The purpose of this research was to examine which is more useful in-phase or anti-phase movement, the execution of exact periodic movement paced by auditory stimulus. The experiment was conducted on 14 right-handed healthy subjects (nine males, five females, mean age 20.6 ± 2.6 years). Informed consent was obtained from all subjects. Each trial took place under four conditions: i) in-phase movement with a frequency of 1 Hz, ii) anti-phase movement with a frequency of 1 Hz, iii) in-phase movement with a frequency of 0.5 Hz, and iv) anti-phase movement with a frequency of 0.5 Hz. The conditions of auditory stimulus were: stimulus intensity of 60 dB, auditory frequency of 1 kHz, and sixty consecutive stimuli per trial. Auditory stimulus was delivered via headphones. The data measured during the experiment were stimulus onset and movement onset times. The time difference between the target time and the movement onset was defined as the synchronization error. The time difference between two successive movement onsets was defined as the inter- movement interval. For data analysis we used: i) root-mean-square (RMS) of synchronization error, ii) RMS of the difference between the inter-stimulus interval and the inter-movement interval, iii) coefficient of variation (CV) of the inter-movement interval, and iv) the autocorrelation function at lag1 of inter-movement interval. At each frequency, data were compared between the in-phase and anti-phase movement conditions, and the paired t-test was used for statistical analysis. At a frequency of 0.5 Hz, there was a significant difference in RMS of the difference between the inter-stimulus interval and the inter-movement interval and CV of inter-movement interval. At a frequency of 1 Hz, there was no significant difference between these two parameters. The results suggest that the periodic movement of one second interval was a habitual and simple movement, and tends to become a self-paced movement. On the other hand, the periodic movement of two-second interval was not so easily self-paced, because anticipation of the stimulus interfered with retention of the time interval, leading to movement dependent on auditory stimulation.
