Influence of spatial and temporal coding on auditory gap detection

This study investigated the effect on gap detection of perceptual channels, hypothesized to be tuned to spatial location or fundamental frequency (f(0 )) Thresholds were measured for the detection of a silent temporal gap betw een two markers. In the first experiment, the markers were broadband noise, presented either binaurally or monaurally. In the binaural conditions, the markers were either diotic, or had a 640-mu s interaural time difference ( ITD) or a 12-dB interaural level difference (ILD). Reversing the ITD across the two markers had no effect on gap detection relative to the diotic cond ition. Reversing the ILD across the two markers produced a marked deteriora tion in performance. However, the same deterioration was observed in the mo naural conditions when a 12-dB level difference was introduced between the two markers. The results provide no evidence for the role of spatially tune d neural channels in gap detection. In the second experiment, the markers w ere harmonic tone complexes, filtered to contain only high, unresolved harm onics. Using complexes with a fixed spectral envelope, where the f(0) (of 1 40 or 350 Hz) was different for the two markers, produced a deterioration i n performance, relative to conditions where the f(0) remained the same. A l arger deterioration was observed when the two markers occupied different sp ectral regions but had the same f(0). This supports the idea that periphera l coding is dominant in determining gap-detection thresholds when the two m arkers differ along any physical dimension. Higher-order neural coding mech anisms of f(0) and spatial location seem to play a smaller role and no role , respectively. (C) 2000 Acoustical Society of America. [S0001-4966(00)0220 4-9].