Dynamic neuromagnetic responses to auditory motion: a novel index for evaluation of attention.

Our previous studies have demonstrated that there is a motion-related magnetic response evoked by moving sound but not stationary sound. The motion-related response reflects the dynamic activities of brain processing of auditory motion. This study focuses on the effect of attention on the response. Six normal hearing subjects were studied using a 151-channel whole-cortex magnetoencephalography (MEG) system. Four sound stimuli were designed: two sounds moved from left to right (rightward) and the other two sounds moved from right to left (leftward). Two sounds moving in the same direction were separated with an attention task. The attention task was a mathematical calculation. The results showed that when subjects listened to the moving sound, there was a clearly auditory motion related response at a latency of 649 +/- 14.2 ms. However, when subjects were doing the calculation while listening to the moving sounds, the motion related response completely disappeared. Strikingly, there was a dent at a latency of 600 ms. To our knowledge, this is probably the first study showing a neuromagnetic response which can be clearly elicited or inhibited by an attention task. We consider that the motion related response has the potential to be an objective index for the study of attention.