Threshold integration of bi-amplitude signals

This study examined the pattern of intensity integration at threshold. The stimuli studied are unique in that they have a compound peak-to-peak amplitude envelope. This waveform was partitioned into two segments, each having a different peak-to-peak magnitude (bi-amplitude). All signals in the bi-amplitude series were the same duration (100 ms). Therefore, threshold differences between these signals are due solely to the integration of intensity in the amplitude dimension. A prediction of the pattern of thresholds, based on the diverted-input hypothesis, suggested that little or no integration would occur when the amplitude difference between segments is greater than a specific magnitude. Our results indicate that there are similarities in the integration process found with variable duration signals and with bi-amplitude signals. We conclude that previous estimates of the minimum intensity level based on temporal integration data underestimates the intensity levels that can contribute to threshold. Our results suggest that there are no apparent constraints on the intensity levels that can be integrated near threshold. The auditory system integrates distributed stimulus intensity in both the time and amplitude dimensions. Temporal integration in the auditory system can be viewed as a signal process, where an enhanced internal representation is given low-level stimuli.