Abstract
It has been widely reported that the late positive component (P3) of Auditory Evoked Potentials (AEP) was elicited by the onset of task-relevant stimulus. It also has been reported that when the stimuli differ only in duration, the offset of task-relevant tone evokes the AEP with P3. In this study, it was hypothesized that P3 can be evoked by a task-irrelevant tone as well as by a task-relevant one if subject starts processing every tone as the task-relevant one from its onset. The task-relevant tone was a medium-duration tone and prior to the task, the subject was trained to anticipate the cessation of the medium-duration tone (600ms) without actual offset. Results showed that when the duration was short (300ms), P3 was evoked by the offset of tone. However, when it was long (1200ms), P3 was elicited at the time of the offset of the task-relevant tone. These findings were interpreted to mean that the termination of time estimation activity for the task-relevant tone evoked P3 component.
