Age-related changes in auditory temporal processing

Our knowledge of age-related changes in auditory processing in the central auditory system is limited, unlike the changes in the peripheral hearing organs which are more extensively studied. These changes in the central auditory pathway primarily manifest as changes in processing of temporally complex stimuli. This study aims to understand age-related changes in temporal processing in a rodent model system using non-invasive auditory evoked potentials and comparing these to single neuron responses from the inferior colliculus (IC), a primary generator of these responses. Envelope following responses (EFRs) were recorded from young and aged Fischer-344 rats using subdermal needle electrodes, and dual channels in anesthetized and un-anesthetized conditions. The stimuli used to evoke these responses were sinusoidally amplitude tones changing in modulation frequency, modulation depth, envelope shape and sound level of presentation, as well as sinusoidally frequency modulated tones. Single neuron responses from the IC of these young and aged animals were recorded for the same stimuli and differences in rate and temporal discharge coding were investigated. The evoked potentials indicate that responses to these stimuli are similar between the young and aged animals for slower modulation frequencies and higher modulation depths. However, significant deficits began to emerge with age when the modulation cues were reduced or altered, even when changes in hearing sensitivity were compensated. Aged animals exhibit decreased response amplitudes with faster modulation frequencies and decreased modulation depths. Dual channel recordings indicate that the two channels are sensitive to a complementary range of modulation frequencies, and provide a greater understanding of these age-related deficits. Responses from IC neurons correlate with these changes, exhibiting lower cutoff frequencies and higher depth thresholds in synchronous responses with age. These results indicate that age related temporal processing deficits become apparent only under difficult listening conditions, and standard diagnostic testing methods in quiet may not be sufficient for fully understanding age-related hearing changes that could affect quality of life. This work also has implications for constraining the responsible cellular and network mechanisms as well as rapid testing of therapeutic interventions including auditory training or pharmacological treatments

A data-driven approach to identify a rapid screener for auditory processing disorder testing referrals in adults

Abstract Hearing thresholds form the gold standard assessment in Audiology clinics. However, ~ 10% of adult patients seeking audiological care for self-perceived hearing deficits have thresholds that are normal. Currently, a diagnostic assessment for auditory processing disorder (APD) remains one of the few viable avenues of further care for this patient population, yet there are no standard guidelines for referrals. Here, we identified tests within the APD testing battery that could provide a rapid screener to inform APD referrals in adults. We first analyzed records from the University of Pittsburgh Medical Center (UPMC) Audiology database to identify adult patients with self-perceived hearing difficulties despite normal audiometric thresholds. We then looked at the patients who were referred for APD testing. We examined test performances, correlational relationships, and classification accuracies. Patients experienced most difficulties within the dichotic domain of testing. Additionally, accuracies calculated from sensitivities and specificities revealed the words-in-noise (WIN), the Random Dichotic Digits Task (RDDT) and Quick Speech in Noise (QuickSIN) tests had the highest classification accuracies. The addition of these tests have the greatest promise as a quick screener during routine audiological assessments to help identify adult patients who may be referred for APD assessment and resulting treatment plans