Task-contingent enhancement of the auditory evoked response

The level of the enhancement to a stimulus of constant intensity that signaled that successful completion of the task was related to the degree of the intensity difference between it and a stimulus that signaled the unsuccessful completion ofThe task.

Abstract

Abstract Twenty-four human subjects were required to make voluntary horizontal saccades by following an oscilloscope beam. A “successful” saccade was determined by a logic circuit that was triggered only when the electro-oculogram showed a deflection that was both accurately timed to the oscilloscope beam and of a predefined amplitude. After “successful” saccades a click that was approximately 30 dB above masked threshold was presented (triggered click). The intensity of the click that followed “unsuccessful” saccades (non-triggered click) was varied in four different experimental conditions so that is was the same intensity as the triggered click, 6 dB less intense, 18 dB less intense, or below threshold. The responses to 32 triggered clicks were averaged for each condition from a vertex electrode. The amplitudes of the averaged evoked response (AER) components were measured for each condition using temporal criteria. Statistical analyses showed that for the triggered click both P2 and P3 (positive peaks at 200 and 300 msec, respectively) increased as the intensity of the non-triggered click decreased. Thus, the degree of the enhancement to a stimulus of constant intensity that signaled that successful completion of the task was related to the degree of the intensity difference between it and a stimulus that signaled the unsuccessful completion of the task. Control conditions showed that the effects could not be attributed to eye movement artifacts.