The auditory 2-stimulus oddball paradigm was employed in the following tests, and the stimuli were defined as ‘standard’ and ‘target’ and were presented with a probability of 0.85 and 0.15, respectively. A 500-Hz tone was defined for the standard stimulus, and a 1-kHz tone was defined for the target stimulus. The tones were presented binaurally through earphones at 70 dB SPL once every 2 s, and each stimulus lasted for 100 ms. Subjects were instructed to press a button as quickly and accurately as possible following identification of a target stimulus, and the reaction time and error rates were recorded. The experiments were performed in a shielded room free from noise or interruption.
