2015 Volume 14 Issue 1 Pages 7-15
Reaction time for memory-guided saccade shortens during maintenance of neck flexion. The present study applied transcranial magnetic stimulation (TMS) to the frontal oculomotor field, and was investigated the effect of maintaining neck flexion on information processing time in the neural pathway of memory-guided saccade before the frontal oculomotor field. The reaction time was measured with the chin resting on a stand (chin-on condition) and with voluntary maintenance of neck flexion (chin-off condition) at 80 % maximal neck flexion angle, with and without TMS. TMS timing producing the longest prolongation of the reaction time was first roughly identified for 10 ms intervals from 0 to 180 ms after the lights-out of central fixation point. Thereafter, TMS timing was set finely at 2 ms intervals from －20 to ＋20 ms of the 10 ms interval producing the longest prolongation. The reaction time without TMS was significantly shorter (25.6 ms) for the chin-off condition (231.6 ± 44.6 ms) than the chin-on condition (256.6 ± 45.9 ms). TMS timing producing maximal prolongation of the reaction time was significantly earlier (23.3 ms) for the chin-off condition (102.6 ± 16.8 ms) than the chin-on condition (125.8 ± 13.6 ms). The ratio of the forward shift in TMS timing relative to the shortening of reaction time was 93.2 %. We confirmed that information processing time in the neural pathway of the memory-guided saccade before the frontal oculomotor field shortened with maintaining neck flexion, and that the reduction accounted for approximately 93 % of the shortening of reaction time.