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

Abstract

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.

Encoding of speech sounds with frequency-following response in infants with Congenital Zika Syndrome: A case-controlled study

“…Besides that, the findings of wave V delays have also been found in children with the presence of neurophysiological changes in individuals exposed to other neonatal infections, such as congenital toxoplasmosis, autism spectrum disorder, dyslexia, and auditory neuropathy 17,18,[30][31][32][33] . This deficit might be associated with behavioral difficulties agreeing with the findings of other researchers 16 who propose that prenatal exposure to the Zika virus may disrupt auditory development.…”

“…The infants afflicted with toxoplasmosis exhibited elevated reactions in the latency measurements of waves V, A, E, F, and O waves, and diminished reactions in wave amplitude measurements A and F 17 . Another study showed that there seems to be damage in the FFR responses in individuals with auditory neuropathy, but only in the condition in which there is the presence of competitive noise 18 .…”