Auditory evoked potentials to changes in interaural cross correlation

The objective of this study is to analyze the representation of specific binaural stimulus features in the human brain and to compare the results to psychoacoustic data. Late auditory evoked potentials to changes in the interaural cross correlation (IACC) of continuous bandpass noise (100–2000 Hz) were recorded, 1000 sweeps per stimulus condition were averaged. In experiment 1 a brief ‘‘binaural gap’’ with a gap IACC was interposed in the noise with a reference IACC. N1 and P2 amplitudes increased with increasing gap duration. For uncorrelated reference IACC (0/1/0 and 0/−1/0 conditions) objective thresholds were comparable to psychoacoustic data. For uncorrelated gap IACC (1/0/1 and −1/0/−1 conditions) objective thresholds were about four times larger than in psychoacoustic measurements. In experiment 2 reference and test interval had the same length of 800 ms and the magnitude of change in IACC was varied. Objective IACC-JNDs are larger for an uncorrelated reference than for IACCs of ±1. For the uncorrelated reference, test IACCs towards +1 elicited larger AEP components than test IACCs towards −1. In contrast to binaural difference potentials used at the brain stem level, employing changes in IACC constitutes a more direct approach to objectively investigate the binaural system in humans.