Cortical evoked potentials in response to brief modulation of signal amplitude

Abstract

Human cortical evoked potentials were monitored with scalp electrodes as an indicator of the ability to resolve brief changes in an auditory signal. For a brief period in the middle of a noise pulse its intensity was increased or decreased. The magnitude and duration of this change was varied to establish (1) the threshold for the cortical evoked potential and (2) the effect on the evoked response (amplitude, latency) in the suprathreshold region. To evoke a stimulus-specific potential pattern, durations of about 16 ms were required for intensity changes of +3 dB. With an intensity step of +9 dB, the threshold duration was reduced to 4-6 ms. A brief increase in intensity was more associated with distinctly lower thresholds and larger response amplitudes than an equivalent reduction in intensity, duration being equal. These results confirm the critical durations found in psychoacoustic studies that offer valuable evidence as to the ability to resolve brief changes in an auditory signal.

Perceptual asymmetries associated with changing-loudness aftereffects

“…The responses to changing sound level in cortical evoked potentials are greater for increasing sound level than for decreasing sound level (Arlinger & Jerlvall, 1979;Martin & Boothroyd, 2000;Wedel, 1982). Two studies concerned the responses of neurons in the cat's auditory cortex to diotic changing sound level and dichotic differences in changing sound level, simulating auditory motion-in-depth and azimuthal motion, respectively.…”