Neural Representation of Interaural Time Differences in Humans—an Objective Measure that Matches Behavioural Performance

Abstract

Humans, and many other species, exploit small differences in the timing of sounds at the two ears (interaural time difference, ITD) to locate their source and to enhance their detection in background noise. Despite their importance in everyday listening tasks, however, the neural representation of ITDs in human listeners remains poorly understood, and few studies have assessed ITD sensitivity to a similar resolution to that reported perceptually. Here, we report an objective measure of ITD sensitivity in electroencephalography (EEG) signals to abrupt modulations in the interaural phase of amplitude-modulated low-frequency tones. Specifically, we measured following responses to amplitude-modulated sinusoidal signals (520-Hz carrier) in which the stimulus phase at each ear was manipulated to produce discrete interaural phase modulations at minima in the modulation cycle—interaural phase modulation following responses (IPM-FRs). The depth of the interaural phase modulation (IPM) was defined by the sign and the magnitude of the interaural phase difference (IPD) transition which was symmetric around zero. Seven IPM depths were assessed over the range of ±22 ° to ±157 °, corresponding to ITDs largely within the range experienced by human listeners under natural listening conditions (120 to 841 μs). The magnitude of the IPM-FR was maximal for IPM depths in the range of ±67.6 ° to ±112.6 ° and correlated well with performance in a behavioural experiment in which listeners were required to discriminate sounds containing IPMs from those with only static IPDs. The IPM-FR provides a sensitive measure of binaural processing in the human brain and has a potential to assess temporal binaural processing.

Electrophysiological and Behavioral Evidence of Reduced Binaural Temporal Processing in the Aging and Hearing Impaired Human Auditory System

“…Neural IPD processing was investigated electrophysiologically by means of interaural phase modulation—following responses (IPM-FRs; Haywood et al., 2015 ; McAlpine et al., 2016 ; Undurraga et al., 2016 ). The IPM-FRs were evoked by IPMs, that is, periodic changes in IPDs over time that were embedded in the TFS of acoustic stimulation.…”

“…To this end, this study examined neural and behavioral IPD processing in six participant groups: young, middle-aged, and older participants, with either normal hearing (NH) thresholds or sensorineural HI (i.e., originating at cochlear or neural level). Neural IPD processing was studied electrophysiologically using a recently developed measure that records neural responses to periodic changes in IPDs over time, embedded in the TFS of acoustic stimuli ( Haywood, Undurraga, Marquardt, & McAlpine, 2015 ; McAlpine, Haywood, Undurraga, & Marquardt, 2016 ; Undurraga, Haywood, Marquardt, & McAlpine, 2016 ). In addition, behavioral IPD processing was examined through IPD discrimination thresholds, obtained for similar stimuli as those applied during the electrophysiological measurements.…”

Objective assessment of electrode discrimination with the auditory change complex in adult cochlear implant users

“…Eye movement and eye blink artefact were removed by means of a standard correlation subtraction. EEG responses were de-noised using spatial filtering (Cheveigné and Simon, 2008;Undurraga et al, 2016) as follows:…”

Neural signatures of disordered multi-talker speech perception in adults with normal hearing

“…differences (McAlpine et al, 2016;Undurraga et al, 2016;Haywood et al, 2015;Ross et al, 2007). 14 In this task, the phase of a 500Hz tone presented to each ear was shifted by a variable amount (up to 15 180°), creating the percept of a tone that moved from the center to the sides of the head.…”

“…14 In this task, the phase of a 500Hz tone presented to each ear was shifted by a variable amount (up to 15 180°), creating the percept of a tone that moved from the center to the sides of the head. To eliminate 16 phase transition artifacts, an amplitude modulation of ~41 Hz was imposed on the tone, such that the 17 instantaneous phase shift always coincided with the null of the amplitude envelope ( Figure 3A) 18 (Undurraga et al, 2016;Haywood et al, 2015). To test psychophysical thresholds for binaural sTFS cues, 19…”