Auditory time-intensity cues in the binaural interaction component of the auditory evoked potentials

David L Mcpherson,Arnold Starr

doi:10.1016/0378-5955(95)00134-1

David L Mcpherson, Arnold Starr

Open Access

https://doi.org/10.1016/0378-5955(95)00134-1

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Abstract

Binaural interaction in the brainstem and middle latency auditory evoked potentials to intensity (d I) and timing differences (d T) between the two ears was studied in 10 normal hearing young adults. A component reflecting binaural interaction in the brainstem potentials occurred at approximately 7 ms and was of largest amplitude when d I and d T were 0. The latency of the binaural interaction component gradually shifted and its amplitude decreased as d I or d T increased and binaural interaction became undetectable when d I = 16 dB or when d T ≥ 1.6 ms. In the middle latency potentials binaural interaction components peaking at 20, 32, and 45 ms were defined that were also largest when d I and d T = 0. The latency of the interaction did not shift with changes in d T and d I whereas the amplitude gradually decreased but binaural interaction components were still evident even at the largest values of d I (30 dB) and d T (3 ms). Psychophysical judgements of binaural perceptions showed binaural fusion of the stimuli to persist with d T values up to 1.6 ms and that lateralization of the intracranial image was complete when either d T = 1.6 ms or when d I = 16 dB. The results suggest that the presence of a binaural interaction component of auditory brainstem potentials correlates with the fusion of binaural click stimuli and the amplitude of the binaural interaction component correlates inversely with the degree of lateralization of the intracranial image. Binaural interaction components of middle latency potentials persist and continue to change even after the binaural stimuli cannot be fused.

Highlights

Binaural interaction (BI) in the auditory evoked potentials may be defined as the difference between the algebraic sum of the monaural evoked potentials and the binaurally evoked potential
The BI component was absent for interaural timing differences greater than 1.2 ms or for interaural loudness differences greater than about 30 dB, values at which Furst and colleagues reported that their subjects no longer fused the images or, if fused, the images were not localized intracranially but were completely lateralized
Informed consent was obtained from each subject and the investigation was performed in accordance with the principles of the Declaration of Auditory evoked potentials were recorded between electrodes positioned at Cz and a non-cephalic electrode positioned over Cvii

Summary

Introduction

Binaural interaction (BI) in the auditory evoked potentials may be defined as the difference between the algebraic sum of the monaural evoked potentials and the binaurally evoked potential. BI can be demonstrated in brainstem ( 5 - 8 ms), middle ( 2 0 - 4 0 ms) and long-latency ( 9 0 - 2 0 0 ms) auditory evoked potentials as a reduction in the amplitude of the binaurally evoked potentials compared to the sum of the monaurally evoked potentials. There are several studies that have examined the relationship between perceptual features of binaural signals and the BI components. Furst et al (1985) found that the first major peak of the BI component to click stimulation occurring at about 7.5 ms was observable only when the binaural signals were perceptually fused and localized intracranially. The authors suggested that whenever the BI component is present, the binaural stimuli are perceived as a single fused image within the head

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