Children with amblyaudia show less flexibility in auditory cortical entrainment to periodic non-speech sounds

Abstract

We investigated auditory temporal processing in children with amblyaudia (AMB), a subtype of auditory processing disorder, via cortical neural entrainment. Evoked responses were recorded to click-trains at slow versus fast (8.5 versus 14.9/sec) rates in n = 14 children with AMB and n = 11 age-matched controls. Source and time-frequency analyses decomposed EEGs into oscillations (reflecting neural entrainment) stemming from the bilateral auditory cortex. Phase-locking strength in AMB depended critically on the speed of auditory stimuli. In contrast to age-matched peers, AMB responses were largely insensitive to rate manipulations. This rate resistance was seen regardless of the ear of presentation and in both cortical hemispheres. Children with AMB show a stark inflexibility in auditory cortical entrainment to rapid sounds. In addition to reduced capacity to integrate information between the ears, we identify a new functional characterization of AMB in the form of more rigid tagging of external auditory stimuli. Our neurophysiological findings may account for certain temporal processing deficits commonly observed in AMB and related auditory processing disorders (APDs) behaviorally. More broadly, our findings may inform communication strategies and future rehabilitation programs; increasing the rate of stimuli above a normal (slow) speech rate is likely to make stimulus processing more challenging for individuals with AMB/APD.

Effects of stimulus rate and periodicity on auditory cortical entrainment to continuous sounds

“…Having the same result, however, it is possible that individuals who show better brain-to-acoustic coupling relegate temporal processing to lower levels of the auditory system (e.g., brainstem, thalamus), more peripheral to the behavior and cortical responses assessed here. Whereas others who perform worse or more laboriously in temporal processing tasks might require high levels of auditory processing at the cortical level as a form of compensatory mechanism (Momtaz et al, 2021; Momtaz et al, 2022). This might account for the counterintuitive negative correlation we find between cortical phase-locking strength and behavior, i.e., more effortful encoding (higher PLV) in less perceptually sensitive individuals.…”

“…A summary of the major findings of our study is provided Table 1. Having revealed speech is particularly rate and periodicity sensitive (more so than nonspeech clicks), this might inform broader work examining temporal processing issues in patient populations such as those with certain auditory processing disorders (Momtaz et al, 2021;Momtaz et al, 2022) or dyslexia (Ben-Yehudah et al, 2004;Tallal et al, 1993) which impact auditory temporal processing. The data here characterize the constraints of temporal capabilities in auditory cortex and neural entrainment.…”

“…We used BESA Research 7.1 (BESA, GmbH) to preprocess the continuous EEG data for token-level time-frequency analysis (TFA). TFA was otherwise similar to our previous reports (Momtaz et al, 2022). Recordings were epoched into single trials from -10 ms to 56 ms and bandpass filtered from 10 to 2000 Hz (zero-phase Butterworth filters; slope = 48 dB/octave).…”

“…In the context of speech, oscillatory neural entrainment is the process by which auditory cortical activity precisely tracks and adjusts to modulations in the speech amplitude envelope via phase alignment between the neural and acoustic signal (Lakatos et al, 2019; Pikovsky et al, 2002). Entrainment is one of several important functions in auditory processing that can make communication seem effortless and automatic to healthy listeners and conversely, difficult in individuals with language learning disorders (Momtaz et al, 2021; Momtaz et al, 2022).…”

“…Entrainment is one of several important functions in auditory processing that can make communication seem effortless and automatic to healthy listeners and conversely, difficult in individuals with language learning disorders (Momtaz et al, 2021;Momtaz et al, 2022).…”