Spectral integration in binaural processing

Abstract

Results are reported from human psychophysical and animal neurobehavioral experiments that examined the ability of the binaural system to integrate information across frequency channels. The psychophysical experiments measured the lateralization of low-frequency (<1200 Hz) multitone complexes as a function of number of components (five or fewer) and frequency spacing between these components (25 to 400 Hz). A pointing task was used to match the perceived lateral position of a broadband noise burst to that of the complex. The complex contained a fixed interaural delay of 1500 μs leading to the left, and the pointer’s perceived lateral position was adjusted by varying its interaural level difference. Parallel neurophysiological experiments were conducted in the optic tectum (superior colliculus) of the barn owl, using narrow-band dichotic noise bursts and multitone stimuli; the localization behavior of the owl in response to these same stimuli was also measured. Results show complex patterns of responses with implications for models of frequency interaction in the binaural system. Linear multiplicative or additive models customarily used in cross-correlation analysis do not explain the entire data set. [Work supported by NIH.]