Auditory evoked brain responses: Comparison of ON and OFF responses at long and short durations

Abstract

Average evoked brain responses (EBRs) to three durations of one kilohertz pure-tone stimuli were computed from human scalp recordings. Stimuli of 25,75, and 2,000 msec duration were each presented binaurally at each of eight equally spaced intensity levels, ranging from 58 to 86 dB SPL. EBRs computed immediately following presentation, and immediately following removal of the 2,000-msec-duration stimulus result in ON and OFF responses, respectively. EBRs computed immediately following presentation of the 25-and 75-msec-duration stimuli appear to be the result of the sum of separate responses to stimulus onset and offset. Computerdissected ON and OFF EBRs to short-duration stimuli are very similar in waveform and amplitude to the responses evoked by the onset and offset, respectively, of the 2,000-msec duration stimulus. Dissected ON and OFF responses demonstrate linear amplitude-intensity functions in amplitude ranges similar to respective ON and OFF responses to 2,000-msec stimulation. The data suggest that ON and OFF responses are mediated by independent physiological mechanisms.

ON and OFF components in the auditory evoked potential

“…The mean N 1 and Ps latencies were 93 and 180 msec in the AEP to the 25-msec tones, 92 and 169 msec in the 2,OOO-ON response, that the amplitude of the Ni-P, response to the onset of a toneburst varies as a function of the duration of the preceding silent interval. Thus, in Schweitzer's (1977) experiments, the AEP to the 25-msec tone might have differed from the ON response to the 2,OOO-msec tone because the former was preceded by a longer silent interval, not because it contained an additional OFF component. To evaluate this question, we first replicated one of Schweitzer's experimental conditions, using a 4-sec interstimulus interval (lSI), and compared those AEPs with AEPs elicited to the same stimuli delivered at to-sec ISis.…”

“…If, as suggested by these results, there is little interaction between ON and OFF responses at short intervals, the AEP to a brief sound would consist of overlapping, independent responses to its onset and offset (Spreng, 1969). Recent experiments by Schweitzer (1977) were interpreted as supporting this' hypothesis. Subtraction of the ON response to the beginning of a 2,OOO-msec tone from the AEP to a brief (25 or 75 msec) tone yielded a waveform that was grossly similar in amplitude and morphology to the OFF response which occurred at the end of a 2,OOO-msec tone.…”

“…25-msec toneburst could be "dissected" into separate ON and OFF responses (Schweitzer, 1977) when the confounding variable of interstimulus interval was controlled.…”

Evoked brain responses to auditory and visual stimuli of equal subjective magnitude

“…The findings that EBRs to bimodal stimuli seem to be the simple algebraic sum of two unimodal EBRs suggest that little, if any, sensory interaction occurred. The notion of simple algebraic summation of waveforms has been suggested previously (Schweitzer, 1977;Tepas & Walsh, Note 3). Thus, linear amplitudeintensity relations to bimodal stimulation should not, necessarily, be expected.…”

“…It is now well established that the amplitude of the evoked brain response (EBR) is related to changes in auditory (Davis & Zerlin, 1966;Keidel & Spreng, 1965;Schweitzer, 1977;Tepas, Boxerman, & Anch, 1972) and visual (Dinges & Tepas, 1976;Kress, 1975;Shipley, Jones, Wayne, & Fry, 1966;Tepas, Guiteras, & Klingaman, 1974) stimulus intensity. Although these relationships are most frequently linear, their exact form is not clear.…”