Age-Related Deficits in Electrophysiological and Behavioral Measures of Binaural Temporal Processing

Abstract

Binaural processing, particularly the processing of interaural phase differences, is important for sound localization and speech understanding in background noise. Age has been shown to impact the neural encoding and perception of these binaural temporal cues even in individuals with clinically normal hearing sensitivity. This work used a new electrophysiological response, called the interaural phase modulation-following response (IPM-FR), to examine the effects of age on the neural encoding of interaural phase difference cues. Relationships between neural recordings and performance on several behavioral measures of binaural processing were used to determine whether the IPM-FR is predictive of interaural phase difference sensitivity and functional speech understanding deficits. Behavioral binaural frequency modulation detection thresholds were measured to assess sensitivity to interaural phase differences while spatial release-from-masking thresholds were used to assess speech understanding abilities in spatialized noise. Thirty adults between the ages of 35 to 74 years with normal low-frequency hearing thresholds were used in this study. Data showed that older participants had weaker neural responses to the interaural phase difference cue and were less able to take advantage of binaural cues for speech understanding compared to younger participants. Results also showed that the IPM-FR was predictive of performance on the binaural frequency modulation detection task, but not on the spatial release-from-masking task after accounting the effects of age. These results confirm previous work that showed that the IPM-FR reflects age-related declines in binaural temporal processing and provide further evidence that this response may represent a useful objective tool for assessing binaural function. However, further research is needed to understand how the IPM-FR is related to speech understanding abilities.

Impaired Binaural Hearing in Adults: A Selected Review of the Literature

“…Note that while there is no onset or offset difference in amplitude or phase, the phases of the signals at the left and right ears (top and bottom waveforms) are continually changing, resulting in an interaural phase difference that changes over time and an interaural time difference that shifts from left-leading to right-leading and back again. Reproduced under Creative Commons reuse license from Koerner et al (2020). (Papesh et al, 2017; extended this to electroencephalography (EEG).…”

“…The P1-N1-P2 complex, which is measured in the time domain, arises at multiple levels of the thalamus and AC ( Haywood et al, 2015 ). More recently ( Haywood et al, 2015 ; Anderson et al, 2018 ; Vercammen et al, 2018 ; Koerner et al, 2020 ) researchers have used sequences of stimuli that changed rapidly (<7 Hz) in binaural configuration and measured the interaural phase modulation following response (IPM-FR). These responses are believed to be generated from the same sites as the P1-N1-P2 complex, but the steady-state nature allows them to be examined in the frequency domain.…”

“…Panel (D) shows the response to a diotic stimulus and thus does not contain the peaks indicating the presence of the IPM-FR but does show the response to the modulation of the carrier amplitude at 81.6 Hz. Reproduced with permission from Ross et al (2007) ; Vercammen et al (2018) , and Koerner et al (2020) . Vercammen et al copyright 2018, Sage Publications.…”

“…While the electrophysiological and behavioral responses at the level of the cortex are fairly strong for these and other binaural tasks ( Papesh et al, 2017 ), some electrophysiological measures ( Anderson et al, 2018 ) show poor relationships with binaural sensitivity. In addition, some research ( Koerner et al, 2020 ) has found a diversity of relationships between neurophysiological responses and different behavioral tasks in the same listeners. Koerner et al (2020) were the first to use a behavioral task that used a stimulus that was directly comparable to the IPM-FR stimulus and found no relationship between the behavioral results and aging or behavioral thresholds and neural amplitudes.…”

“…In addition, some research ( Koerner et al, 2020 ) has found a diversity of relationships between neurophysiological responses and different behavioral tasks in the same listeners. Koerner et al (2020) were the first to use a behavioral task that used a stimulus that was directly comparable to the IPM-FR stimulus and found no relationship between the behavioral results and aging or behavioral thresholds and neural amplitudes. In the same listeners, however, the SRM task used by Papesh et al (2017) was correlated with the amplitude of the neural response at an individual level.…”