14 Feb Brain Biomarkers May Lead to Clinical Tests for Hidden Hearing Loss
MedicalResearch.com Interview with:
Aravindakshan Parthasarathy, PhD
Researcher, Massachusetts Eye and Ear
Instructor in Otolaryngology–Head and Neck Surgery
Harvard Medical School
MedicalResearch.com: What is the background for this study? Would you briefly explain what is meant by Hidden Hearing Loss?
Response: Our ears were not designed for the society our brains created. The World Health Organization estimates that 1 billion young adults are at risk for hearing loss due to prolonged exposure to excessive environmental noise. Anatomical analysis of human ears has shown that half of the nerve fibers connecting the ear to the brain have degenerated by the time we reach 40 years of age. Many of us experience the first symptoms of hearing loss as a difficulty following conversations in crowded places such as restaurants.
Hidden hearing loss is an umbrella term used to describe such hearing difficulties experienced by people who show no abnormalities on any of the current tests of hearing used in the clinic. Approximately 10% of visitors to our hospital hearing clinic fit this profile, arriving with a primary complaint of poor hearing but being sent home with a clean bill of hearing health.
MedicalResearch.com: What are the main findings?
Response: We set out to identify objective physiological biomarkers that would reveal auditory processing dysfunction in subjects with clinically normal hearing that struggle to understand speech in multi-talker environments. We identified a few simple behavioral and physiological tests in adult humans that could be combined to account for nearly 80% of the variability in multi-talker speech intelligibility, a significant improvement over current clinical tests of hearing which do not detect these changes at all. The tests included measuring cognitive load during a challenging listening task, and measuring the neural encoding of subtle shifts in frequency using electrodes placed in the ear canal.
MedicalResearch.com: What should readers take away from your report?
Response: Our findings show that poor multi-talker speech intelligibility reflects a confluence of disordered bottom-up neural processing and an over-reliance on top-down cognitive listening effort. The key markers for multi-talker speech intelligibility identified here do not require specialized equipment or marathon measurement sessions and in theory, could be implemented into most hospital hearing clinics.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: Future research will focus on ways to implement these tests in the hearing clinic, which could provide patients with an objective measure for their perceptual difficulties and provide hearing health providers with an objective readout for their therapeutic drugs or devices. Complementary studies in animal models will investigate the biological mechanisms that underlie deficits seen in the clinical tests.
The authors declare no competing interests.
Bottom-up and top-down neural signatures of disordered multi-talker speech perception in adults with normal hearing
Aravindakshan Parthasarathy , Kenneth E Hancock, Kara Bennett, Victor DeGruttola, Daniel B Polley
Massachusetts Eye and Ear Infirmary, Harvard Medical School
Bennett Statistical Consulting Inc, Harvard TH Chan School of Public Health
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