FIGURE 3.

Experimental procedure: The target stimuli were 100 Hz with the duration of 150 ms, the disturbances were 23 Hz with the duration of 200 ms. Each run consisted of eight blocks with only one target site (left or right) stimulated in one block, and each block contained 13 trials. Each trial contained six stimuli, in which the only one target stimulus was selected pseudorandomly, and others were disturbances. The first trial in each block was all six disturbance stimuli to mark the start of the block.