Abstract:
Numerous psychophysical studies have demonstrated that behavioral detection thresholds decrease with increasing stimulus duration, often referred to as the time-intensity trade. Few studies, however, have evaluated the physiological correlates of this trading relationship. The purpose of the present study was to examine the effect of stimulus duration on evoked potential thresholds known as the auditory late response (ALR). Behavioral and ALR thresholds were estimated for 1000 and 4000 Hz tone bursts at 8, 16, 32, 64, and 128 ms in five normal-hearing, young adults. Evoked responses were recorded in 2-dB steps from 20 dB to -4 dB SL re: behavioral threshold. ALR threshold was estimated as the lowest level at which the N1-P2 complex was visually detected by two independent judges. Preliminary results show that both behavioral and ALR thresholds decreased as a function of increasing duration. For the 1000-Hz stimulus, both ALR and behavioral thresholds decreased by approximately 23 dB HL over the range of durations tested. Average ALR and behavioral thresholds for the 4000-Hz stimulus decreased by about 19 dB HL. These results show that the time-intensity trade can be demonstrated physiologically using the auditory late response.