Auditory stimulus processing at different stimulus intensities as reflected by auditory evoked potentials.

The influence of stimulus intensity on the components of auditory evoked potentials was investigated at different levels of attention and task relevance in six healthy adult subjects. A negative component with a latency of 130 msec (N130) was produced by stimuli applied as targets or nontargets in a random sequence. The N130 amplitude had an inverse U-shaped relationship to stimulus intensity, with its maximum value at a stimulus intensity of 70 dB SL. The P300 latency showed a U-shaped relationship to stimulus intensity and obtained its minimum value at 70 dB. Thus, evoked-potential equivalents of cognitive auditory stimulus processing could be shown to be loudness driven and to have highest amplitudes or shortest latencies at a stimulus loudness of 70 dB SL.