Neural correlates of extremely large individual differences in interaural cross-correlation detection

Abstract

Interaural cross-correlation is a primary feature that can predict the detection of dichotic signals in background noise. Perfectly correlated noise presented to the two ears is perceived as compact and centrally lateralized. As noise is binaurally de-correlated, the perceptual image widens and becomes more diffuse. Previous investigators have reported large variability across individuals' cross correlation just-noticeable differences (IACC-JNDs). Anecdotally, many listeners with normal pure tone thresholds present as extreme outliers in binaural tasks. It is unknown whether or not this variability across individuals is reflected in the neural activity recorded during passive listening to these stimuli. IACC-JNDs were measured in a behavioral task and compared to correlation-change evoked potentials using electroencephalography (EEG). Results indicate significantly smaller cortical responses (N1 and P2 amplitudes) to interaural change differences for individuals with large- compared to small-JND thresholds. Source localization of this effect was observed in multiple subdivisions of the auditory cortex, include Heschl's gyrus, planum temporale, and the temporal sulcus. These results provide objective electrophysiological evidence of a binaural processing deficit corresponding to extremely large JND thresholds. Interestingly, these listeners are indeed binaurally disadvantaged despite otherwise normal audiometric profiles and lack of spatial hearing complaints. [Work supported by NIH P01AG009524.]