Masking Differentially Affects Envelope-following Responses in Young and Aged Animals

Abstract

Age-related hearing decline typically includes threshold shifts as well as reduced wave I auditory brainstem response (ABR) amplitudes due to cochlear synaptopathy/neuropathy, which may compromise precise coding of suprathreshold speech envelopes. This is supported by findings with older listeners, who have difficulties in envelope and speech processing, especially in noise. However, separating the effects of threshold elevation, synaptopathy, and degradation by noise on physiological representations may be difficult. In the present study, the effects of notched, low- and high-pass noise on envelope-following responses (EFRs) in aging were compared when sound levels (aged: 85-dB SPL; young: 60- to 80-dB SPL) were matched between groups peripherally, by matching wave I ABR amplitudes, or centrally by matching EFR amplitudes. Low-level notched noise reduced EFRs to sinusoidally amplitude-modulated (SAM) tones in young animals for notch widths up to 2 octaves. High-pass noise above the carrier frequency reduced EFRs. Young animals showed EFR reductions at lower noise levels. Low-pass noise did not reduce EFRs in either young or aged animals. High-pass noise may affect EFR amplitudes in young animals more than aged by reducing the contributions of high-frequency-sensitive inputs. EFRs to SAM tones in modulated noise (NAM) suggest that neurons of young animals can synchronize to NAM at lower sound levels and maintain dual AM representations better than older animals. The overall results show that EFR amplitudes are strongly influenced by aging and the presence of a competing sound that likely reduces or shifts the pool of responsive neurons.

Evolving perspectives on the sources of the frequency-following response

“…Recent animal neurophysiology studies have demonstrated that an FFR similar to that of humans can be recorded in awake monkeys 83 , confirming previous demonstrated analogs between humans and anesthetized non-human animals 37,38,84,85 . Awake animal preparations could be particularly enlightening because of the possibility of recording simultaneously from multiple sites in behaving animals.…”

“…The FFR is useful to address questions concerning impaired auditory processing in populations with impaired cochlear function 23–26 , and in neurodevelopmental speech and language disorders 27–32 or autism 33,34 . It can also be used to study maturational 35,36 and aging-related changes 37,38 , sex differences in auditory functions 39 , and improvement caused by interventions 15,40–42 . More broadly, the FFR can provide an index of neurological health, for instance, in populations with acquired neurological disorders (e.g.…”

Longitudinal Auditory Pathophysiology Following Mild Blast Induced Trauma

“…This dichotomy is ripe for further study since the Hz and 45 Hz modulations represent different temporal processing regimes and components of speech (Rosen 1992). In studies on age-related auditory nerve deficit models and AM-in-noise responses in aged animals, decreased sensitivities to lower SNRs in AM-in-noise in damaged auditory systems have been observed (Parthasarathy et al 2016;Lai et al 2017;Lai and Bartlett 2018). This phenomenon could partly explain the changes seen in 45 Hz AMF.…”

“…For AM in Noise stimuli, the same EFRs were used alongside a 71 Hz sinusoidally AM masker of the same length and onset, with Gaussian noise as the carrier, similar to Lai and Bartlett (Lai and Bartlett, 2018). Noise AM maskers were presented at sound levels of 20dB SNR and 0SNR to the sound level of target AM.…”

Vehicular Noise Pollution: Its Environmental Implications and Strategic Control

“…Affects balance system of squid [113] 9 Physiological Stress [114] 10 Irritation [115] 11 Difficulty in communication [116] 12 Nervousness [117] Animals also suffer human like disabilities like hearing loss, loss in responsiveness, dizziness and disturbance [93]. Traffic noise reduced foraging efficiency in most bats [94].…”