Auditory neural processing in children living with HIV uncovers underlying central nervous system dysfunction.

OBJECTIVE: Central nervous system (CNS) damage from HIV infection or treatment can lead to developmental delays and poor educational outcomes in children living with HIV (CLWH). Early markers of central nervous system dysfunction are needed to target interventions and prevent life-long disability. The frequency following response (FFR) is an auditory electrophysiology test that can reflect the health of the central nervous system. In this study, we explore whether the FFR reveals auditory central nervous system dysfunction in CLWH. STUDY DESIGN: Cross-sectional analysis of an ongoing cohort study. Data were from the child's first visit in the study. SETTING: The infectious disease center in Dar es Salaam, Tanzania. METHODS: We collected the FFR from 151 CLWH and 151 HIV-negative children. To evoke the FFR, three speech syllabi (/da/, /ba/, /ga/) were played monaurally to the child's right ear. Response measures included neural timing (peak latencies), strength of frequency encoding (fundamental frequency and first formant amplitude), encoding consistency (inter-response consistency), and encoding precision (stimulus-to-response correlation). RESULTS: CLWH showed smaller first formant amplitudes ( P  < 0.0001), weaker inter-response consistencies ( P  < 0.0001) and smaller stimulus to response correlations ( P  < 0.0001) than FFRs from HIV-negative children. These findings generalized across the three speech stimuli with moderately strong effect sizes (partial η2 ranged from 0.061 to 0.094). CONCLUSION: The FFR shows auditory central nervous system dysfunction in CLWH. Neural encoding of auditory stimuli was less robust, more variable, and less accurate. As the FFR is a passive and objective test, it may offer an effective way to assess and detect central nervous system function in CLWH.

Subconcussion revealed by sound processing in the brain.

Introduction/Purpose: We tested the hypothesis that an objective measure of auditory processing reveals a history of head trauma that does not meet the clinical definition of concussion. Methods: Division I collegiate student-athletes (n = 709) across 19 sports were divided into groups, based on their sport, using prevailing classifications of "contact" (317 males, 212 females) and "noncontact" (58 males, 122 females). Participants were evaluated using the frequency-following response (FFR) to speech. The amplitude of FFR activity in a frequency band corresponding to the fundamental frequency (F0)-the voice pitch-of the speech stimulus, an outcome reduced in individuals with concussions, was critically examined. Results: We found main effects of contact level and sex. The FFR-F0 was smaller in contact athletes than noncontact athletes and larger in females than males. There was a contact by sex interaction, with the FFR-F0 of males in the contact group being smaller than the three other groups. Secondary analyses found a correlation between FFR-F0 and length of participation in contact sports in male athletes. Conclusion: These findings suggest that the disruption of sensory processing in the brain can be observed in individuals without a concussion but whose sport features regular physical contact. This evidence identifies sound processing in the brain as an objective marker of subconcussion in athletes.

Peripheral Auditory Function in Tanzanian Children Living With HIV With Clinically Normal Hearing.

Importance: Despite normal audiometry, adults living with HIV have lower distortion product otoacoustic emissions (DPOAEs) compared with HIV-negative controls, but the degree of these differences in children living with HIV is unknown. If subclinical auditory deficits are present, results could affect developmental outcomes in children living with HIV (CLWH). Objective: To compare DPOAEs and auditory brainstem responses (ABR) between 2 age- and sex-matched groups of younger children with normal audiometry, 1 infected with HIV and the other uninfected. Design, Setting, and Participants: Cohort study in an infectious disease center in Dar es Salaam, Tanzania. Participants included 340 Tanzanian children aged 3 to 9 years with clinically normal hearing, type A tympanograms bilaterally, and air-conduction thresholds of 20 dB HL or less from 0.5 to 8 kHz. Participants in the cohort repeated testing approximately every 6 months (approximately 2.2 sessions per participant) for a total of 744 total observations. Data were analyzed from March 2020 to January 2022. Main Outcomes and Measures: DPOAE amplitudes from 1.5 to 8 kHz using an f2 to f1 ratio of 1.2 and L1/L2 values of 65/55 dB sound pressure level and click-evoked ABR using a slow (21.1/s) and fast (61.1/s) click rate. Results: A total of 141 CLWH (70 female participants [49.3%]; mean [SD] age, 7.24 [1.67] years) and 199 HIV-negative individuals (99 female participants [49.7%]; mean [SD] age, 7.26 [1.44] years) participated in the study. The groups did not differ significantly in age, static immittance, or air-conduction thresholds. HIV status was independently associated with approximately 1.4 dB (95% CI, -3.28 to 0.30 dB) to 3.8 dB (95% CI, 6.03 to -1.99 dB) lower DPOAE amplitudes at 6 and 8 kHz bilaterally and 0.28 µV (95% CI, 0.01 to 0.33 µV) lower ABR wave V amplitudes in the right ear. Conclusions and Relevance: Consistent with previous findings in young adults, CLWH had slightly, but reliably, lower DPOAEs and ABR wave V amplitudes than HIV-negative controls. The magnitude of these differences was small, but results suggest an early and consistent association between HIV infection or treatment and outer hair cell and auditory brainstem responses in children as young as 3 years. These subclinical changes suggest tracking both auditory function and development outcomes in CLWH is warranted.

Preliteracy assessment in children living with HIV in Tanzania: comparison to results from children living without HIV in Tanzania and the United States.

OBJECTIVE: Children with HIV (CWH) are at increased risk for cognitive and developmental delays. Whether HIV affects literacy development, however, remains unknown. Rapid automatized naming (RAN) tasks offer the simplest preliteracy assessment a child can perform that predicts future reading skills across languages. DESIGN AND METHODS: RAN performance was analyzed cross-sectionally on 473 children (249 children without HIV and 217 CWH; ages 3-9) drawn from a longitudinal study in Tanzania. These data were compared to results from 341 normally developing children without HIV (ages 3-8) from the United States. Participants performed two RAN subtests: colors and objects. RESULTS: RAN object completion was greater than for the RAN color in Tanzanian children. CWH were less likely to complete either subtest and performed worse on the object subtest compared to Tanzanian children without HIV. Compared to the US cohort, the Tanzanian cohort was less likely to complete both subtests - in particular the colors subtest - and showed more variability in responses at younger ages. After approximately age 6, however, the trajectory of improvement between the United States and Tanzania was similar. CONCLUSIONS: CWH performed worse on this per-literacy test, indicating literacy skill development in CWH needs further study. The differences between US and Tanzanian results likely reflect variability in when children learn to name colors and objects. The trajectory of improvement between countries became more similar as the children aged. This study motivates further longitudinal analyses aimed at assessing the developmental trajectory of the RAN, its predictive ability for reading skills, and its link with other preliteracy and cognitive skills.

Neural Processing of Speech Sounds in ASD and First-Degree Relatives.

Efficient neural encoding of sound plays a critical role in speech and language, and when impaired, may have reverberating effects on communication skills. This study investigated disruptions to neural processing of temporal and spectral properties of speech in individuals with ASD and their parents and found evidence of inefficient temporal encoding of speech sounds in both groups. The ASD group further demonstrated less robust neural representation of spectral properties of speech sounds. Associations between neural processing of speech sounds and language-related abilities were evident in both groups. Parent-child associations were also detected in neural pitch processing. Together, results suggest that atypical neural processing of speech sounds is a heritable ingredient contributing to the ASD language phenotype.

Athleticism and sex impact neural processing of sound.

Biology and experience both influence the auditory brain. Sex is one biological factor with pervasive effects on auditory processing. Females process sounds faster and more robustly than males. These differences are linked to hormone differences between the sexes. Athleticism is an experiential factor known to reduce ongoing neural noise, but whether it influences how sounds are processed by the brain is unknown. Furthermore, it is unknown whether sports participation influences auditory processing differently in males and females, given the well-documented sex differences in auditory processing seen in the general population. We hypothesized that athleticism enhances auditory processing and that these enhancements are greater in females. To test these hypotheses, we measured auditory processing in collegiate Division I male and female student-athletes and their non-athlete peers (total n = 1012) using the frequency-following response (FFR). The FFR is a neurophysiological response to sound that reflects the processing of discrete sound features. We measured across-trial consistency of the response in addition to fundamental frequency (F0) and harmonic encoding. We found that athletes had enhanced encoding of the harmonics, which was greatest in the female athletes, and that athletes had more consistent responses than non-athletes. In contrast, F0 encoding was reduced in athletes. The harmonic-encoding advantage in female athletes aligns with previous work linking harmonic encoding strength to female hormone levels and studies showing estrogen as mediating athlete sex differences in other sensory domains. Lastly, persistent deficits in auditory processing from previous concussive and repetitive subconcussive head trauma may underlie the reduced F0 encoding in athletes, as poor F0 encoding is a hallmark of concussion injury.

Peripheral Auditory Function in Young HIV-Positive Adults With Clinically Normal Hearing.

OBJECTIVE: Little is known about peripheral auditory function in young adults with HIV, who might be expected to show early evidence of hearing loss if HIV infection or treatment does affect peripheral function. The goal of this study was to compare peripheral auditory function in 2 age- and gender-matched groups of young adults with clinically normal hearing with and without HIV. STUDY DESIGN: Matched cohort study with repeated measures. SETTING: Infectious disease center in Dar es Salaam, Tanzania. METHODS: Participants included HIV-positive (n = 38) and HIV-negative (n = 38) adults aged 20 to 30 years who had clinically normal hearing, defined as type A tympanograms, air conduction thresholds ≤25 dB HL bilaterally from 0.5 to 8 kHz, and distortion product otoacoustic emissions (DPOAEs) >6 dB above the noise floor bilaterally from 1.5 to 8 kHz. Participants were tested multiple times over 6-month intervals (average, 2.7 sessions/participant) for a total of 208 observations. Primary outcome measures included tympanograms, air conduction audiograms, DPOAEs, and click-evoked auditory brainstem responses. RESULTS: HIV groups did not significantly differ in age, static immittance, or air conduction thresholds. HIV-positive status was independently associated with approximately 3.7-dB lower DPOAE amplitudes from 2 to 8 kHz (95% CI, 1.01-6.82) in both ears and 0.04-µV lower (95% CI, 0.003-0.076) auditory brainstem response wave I amplitudes in the right ear. CONCLUSION: Young adults living with HIV have slightly but reliably smaller DPOAEs and auditory brainstem response wave I amplitudes than matched HIV-negative controls. The magnitude of these differences is small, but these results support measuring peripheral auditory function in HIV-positive individuals as they age.

Multiple Cases of Auditory Neuropathy Illuminate the Importance of Subcortical Neural Synchrony for Speech-in-noise Recognition and the Frequency-following Response.

OBJECTIVES: The role of subcortical synchrony in speech-in-noise (SIN) recognition and the frequency-following response (FFR) was examined in multiple listeners with auditory neuropathy. Although an absent FFR has been documented in one listener with idiopathic neuropathy who has severe difficulty recognizing SIN, several etiologies cause the neuropathy phenotype. Consequently, it is necessary to replicate absent FFRs and concomitant SIN difficulties in patients with multiple sources and clinical presentations of neuropathy to elucidate fully the importance of subcortical neural synchrony for the FFR and SIN recognition. DESIGN: Case series. Three children with auditory neuropathy (two males with neuropathy attributed to hyperbilirubinemia, one female with a rare missense mutation in the OPA1 gene) were compared to age-matched controls with normal hearing (52 for electrophysiology and 48 for speech recognition testing). Tests included standard audiological evaluations, FFRs, and sentence recognition in noise. The three children with neuropathy had a range of clinical presentations, including moderate sensorineural hearing loss, use of a cochlear implant, and a rapid progressive hearing loss. RESULTS: Children with neuropathy generally had good speech recognition in quiet but substantial difficulties in noise. These SIN difficulties were somewhat mitigated by a clear speaking style and presenting words in a high semantic context. In the children with neuropathy, FFRs were absent from all tested stimuli. In contrast, age-matched controls had reliable FFRs. CONCLUSION: Subcortical synchrony is subject to multiple forms of disruption but results in a consistent phenotype of an absent FFR and substantial difficulties recognizing SIN. These results support the hypothesis that subcortical synchrony is necessary for the FFR. Thus, in healthy listeners, the FFR may reflect subcortical neural processes important for SIN recognition.

Listening in the Moment: How Bilingualism Interacts With Task Demands to Shape Active Listening.

While there is evidence for bilingual enhancements of inhibitory control and auditory processing, two processes that are fundamental to daily communication, it is not known how bilinguals utilize these cognitive and sensory enhancements during real-world listening. To test our hypothesis that bilinguals engage their enhanced cognitive and sensory processing in real-world listening situations, bilinguals and monolinguals performed a selective attention task involving competing talkers, a common demand of everyday listening, and then later passively listened to the same competing sentences. During the active and passive listening periods, evoked responses to the competing talkers were collected to understand how online auditory processing facilitates active listening and if this processing differs between bilinguals and monolinguals. Additionally, participants were tested on a separate measure of inhibitory control to see if inhibitory control abilities related with performance on the selective attention task. We found that although monolinguals and bilinguals performed similarly on the selective attention task, the groups differed in the neural and cognitive processes engaged to perform this task, compared to when they were passively listening to the talkers. Specifically, during active listening monolinguals had enhanced cortical phase consistency while bilinguals demonstrated enhanced subcortical phase consistency in the response to the pitch contours of the sentences, particularly during passive listening. Moreover, bilinguals' performance on the inhibitory control test related with performance on the selective attention test, a relationship that was not seen for monolinguals. These results are consistent with the hypothesis that bilinguals utilize inhibitory control and enhanced subcortical auditory processing in everyday listening situations to engage with sound in ways that are different than monolinguals.

Sex differences in auditory processing vary across estrous cycle.

In humans, females process a sound's harmonics more robustly than males. As estrogen regulates auditory plasticity in a sex-specific manner in seasonally breeding animals, estrogen signaling is one hypothesized mechanism for this difference in humans. To investigate whether sex differences in harmonic encoding vary similarly across the reproductive cycle of mammals, we recorded frequency-following responses (FFRs) to a complex sound in male and female rats. Female FFRs were collected during both low and high levels of circulating estrogen during the estrous cycle. Overall, female rodents had larger harmonic encoding than male rodents, and greater harmonic strength was seen during periods of greater estrogen production in the females. These results argue that hormonal differences, specifically estrogen, underlie sex differences in harmonic encoding in rodents and suggest that a similar mechanism may underlie differences seen in humans.

Auditory neurophysiological development in early childhood: A growth curve modeling approach.

OBJECTIVE: During early childhood, the development of communication skills, such as language and speech perception, relies in part on auditory system maturation. Because auditory behavioral tests engage cognition, mapping auditory maturation in the absence of cognitive influence remains a challenge. Furthermore, longitudinal investigations that capture auditory maturation within and between individuals in this age group are scarce. The goal of this study is to longitudinally measure auditory system maturation in early childhood using an objective approach. METHODS: We collected frequency-following responses (FFR) to speech in 175 children, ages 3-8 years, annually for up to five years. The FFR is an objective measure of sound encoding that predominantly reflects auditory midbrain activity. Eliciting FFRs to speech provides rich details of various aspects of sound processing, namely, neural timing, spectral coding, and response stability. We used growth curve modeling to answer three questions: 1) does sound encoding change across childhood? 2) are there individual differences in sound encoding? and 3) are there individual differences in the development of sound encoding? RESULTS: Subcortical auditory maturation develops linearly from 3-8 years. With age, FFRs became faster, more robust, and more consistent. Individual differences were evident in each aspect of sound processing, while individual differences in rates of change were observed for spectral coding alone. CONCLUSIONS: By using an objective measure and a longitudinal approach, these results suggest subcortical auditory development continues throughout childhood, and that different facets of auditory processing follow distinct developmental trajectories. SIGNIFICANCE: The present findings improve our understanding of auditory system development in typically-developing children, opening the door for future investigations of disordered sound processing in clinical populations.

Rhythm, reading, and sound processing in the brain in preschool children.

A child's success in school relies on their ability to quickly grasp language and reading skills, the foundations of which are acquired even before entering a formal classroom setting. Previous studies in preschoolers have begun to establish relationships linking beat synchronization, preliteracy skills, and auditory processing. Beat synchronization involves the integration of sensorimotor systems with auditory and cognitive circuits and, therefore calls on many of the same neural networks as language. Using a drumming task, we analyzed the relationship between children's ability to maintain an isochronous beat with preliteracy skills and frequency following responses (FFRs) in over 150 preschoolers. We show that preschoolers who performed well on the beat synchronization task outscored their peers on all preliteracy measures and had more robust FFRs. Furthermore, the good synchronizers experienced less degradation of certain FFR measures when listening in noise. Together, our results are consistent with the view that rhythm, preliteracy, and auditory processing are interconnected during early childhood.

Clapping in Time With Feedback Relates Pervasively With Other Rhythmic Skills of Adolescents and Young Adults.

Rhythmic expertise is a multidimensional skill set with clusters of distinct rhythmic abilities. For example, the ability to clap in time with feedback relates extensively to distinct beat- and pattern-based rhythmic skills in school-age children. In this study we aimed to determine whether clapping in time would relate to both beat- and pattern- based rhythmic tasks among adolescents and young adults. We assessed our participants on seven tasks: two beat-based tasks (Metronome and Tempo adaptation), two pattern-based tasks (Reproducing rhythmic patterns and Remembering rhythmic patterns), a self-paced drumming task, a task of drumming to a music beat, and a clapping in time task. We found that clapping in time correlated with all other rhythmic tasks, even though some were not mutually related to one another. These results provide insight into the taxonomy of rhythmic skills and support the practice of clapping in time with feedback as a means of developing broad spectrum rhythmic abilities.

Case studies in neuroscience: cortical contributions to the frequency-following response depend on subcortical synchrony.

Frequency-following responses to musical notes spanning the octave 65-130 Hz were elicited in a person with auditory neuropathy, a disorder of subcortical neural synchrony, and a control subject. No phaselocked responses were observed in the person with auditory neuropathy. The control subject had robust responses synchronized to the fundamental frequency and its harmonics. Cortical onset responses to each note in the series were present in both subjects. These results support the hypothesis that subcortical neural synchrony is necessary to generate the frequency-following response-including for stimulus frequencies at which a cortical contribution has been noted. Although auditory cortex ensembles may synchronize to fundamental frequency cues in speech and music, subcortical neural synchrony appears to be a necessary antecedent.NEW & NOTEWORTHY A listener with auditory neuropathy, an absence of subcortical neural synchrony, did not have electrophysiological frequency-following responses synchronized to an octave of musical notes, with fundamental frequencies ranging from 65 to 130 Hz. A control subject had robust responses that phaselocked to each note. Although auditory cortex may contribute to the scalp-recorded frequency-following response in healthy listeners, our results suggest this phenomenon depends on subcortical neural synchrony.

Distinct rhythmic abilities align with phonological awareness and rapid naming in school-age children.

Difficulty in performing rhythmic tasks often co-occurs with literacy difficulties. Motivated by evidence showing that people can vary in their performance across different rhythmic tasks, we asked whether two rhythmic skills identified as distinct in school-age children and young adults would reveal similar or different relationships with two literacy skills known to be important for successful reading development. We addressed our question by focusing on 55 typically developing children (ages 5-8). Results show that drumming to a beat predicted the variability of rapid naming but not of phonological awareness, whereas tapping rhythmic patterns predicted phonological awareness, but not rapid naming. Our finding suggests that rhythmic interventions can be tailored to address PA and RAN deficits specifically in reading disabled children.

Auditory neurophysiology reveals central nervous system dysfunction in HIV-infected individuals.

OBJECTIVE: To test the hypothesis that human immunodeficiency virus (HIV) affects auditory-neurophysiological functions. METHODS: A convenience sample of 68 HIV+ and 59 HIV- normal-hearing adults was selected from a study set in Dar es Salaam, Tanzania. The speech-evoked frequency-following response (FFR), an objective measure of auditory function, was collected. Outcome measures were FFRs to the fundamental frequency (F0) and to harmonics corresponding to the first formant (F1), two behaviorally relevant cues for understanding speech. RESULTS: The HIV+ group had weaker responses to the F1 than the HIV- group; this effect generalized across multiple stimuli (d = 0.59). Responses to the F0 were similar between groups. CONCLUSIONS: Auditory-neurophysiological responses differ between HIV+ and HIV- adults despite normal hearing thresholds. SIGNIFICANCE: The FFR may reflect HIV-associated central nervous system dysfunction that manifests as disrupted auditory processing of speech harmonics corresponding to the first formant.

Auditory Processing Differences in Toddlers With Autism Spectrum Disorder.

Purpose Auditory processing measures have been used in an attempt to understand the relationship between neurological mechanisms and autism spectrum disorder (ASD) symptomatology in school-age children. The focus of the current study was to understand neural auditory processing in 2- to 3-year-olds with ASD. Method Auditory processing measures (click auditory brainstem responses and speech-evoked frequency-following responses) were hypothesized to differ between typically developing children (n = 18) and children with ASD (n = 18). Auditory processing measures were hypothesized to relate to language development in children with ASD. Results The current study found limited differences in auditory processing measures between the two groups. No relationships were found between auditory processing measures and language development measures. Conclusions Future research is necessary to characterize auditory processing in toddlers with ASD. Longitudinal approaches should be considered when studying auditory processing in children with ASD in order to explore its developmental relationship with ASD symptomatology.

Baseline profiles of auditory, vestibular, and visual functions in youth tackle football players.

AIM: Neurosensory tests have emerged as components of sport-related concussion management. Limited normative data are available in healthy, nonconcussed youth athletes. PATIENTS & METHODS/RESULTS: In 2017 and 2018, we tested 108 youth tackle football players immediately before their seasons on the frequency-following response, Balance Error Scoring System, and King-Devick test. We compared results with published data in older and/or and nonathlete populations. Performance on all tests improved with age. Frequency-following response and Balance Error Scoring System results aligned with socioeconomic status. Performance was not correlated across neurosensory domains. CONCLUSION: Baseline neurosensory functions in seven 14-year-old male tackle football players are consistent with previously published data. Results reinforce the need for individual baselines or demographic-specific norms and the use of multiple neurosensory measures in sport-related concussion management.

Performance on auditory, vestibular, and visual tests is stable across two seasons of youth tackle football.

Objective: Few studies have tracked neurologic function in youth football players longitudinally. This study aimed to determine whether changes in tests of auditory, vestibular, and/or visual functions are evident after participation in one or two seasons of youth tackle football.Study Design: Prospective cohort study.Subjects and Methods: Before their 2017 and/or 2018 seasons, male tackle football players (ages 7-14 yrs) completed three tests that tend to exhibit acute disruptions following a concussion: (1) the FFR (frequency-following response), aphysiologic test of auditory function, (2) the BESS (Balance Error Scoring System), a test of vestibular function, and (3) the King-Devick, a test of oculomotor function. We planned to repeat these on all subjects at the end of each season.Results: Performance on neurosensory tests was stable, with no changes observed in FFR or King-Devick and a slight improvement observed in BESS performance across each season. Performance was also stable over two years for the subjects who participated both years. Across-season test-retest reliability correlations were high.Conclusions: In the absence of concussion, young athletes' performance on the FFR, King-Devick, and BESS is stable across one or two seasons of youth tackle football.