Changes in primitive auditory memory in presbycusis and their impact on binaural auditory processing.

BACKGROUND: Presbycusis is common in ageing populations and often causes a significant decline in binaural auditory processing capabilities, disproportionate to peripheral hearing loss. Sound localisation and speech-in-noise segregation depend on processing temporal fine structure (TFS) information in reverberant environments. This requires transient storage and integration of TFS information, which is the primitive auditory memory (PAM) capacity. However, how presbycusis affects PAM remains unclear. Therefore, this study aimed to investigate how PAM is affected by age and hearing loss severity, and whether PAM explains declines in binaural processing abilities.

METHODS: This study included 33 young adults with normal hearing, 45 older adults with normal hearing, and 118 older patients with varying degrees of presbycusis. All patients underwent a break-in-correlation test to assess the PAM capacity. Binaural auditory processing abilities were evaluated using the Speech Reception Threshold in Noise, Competing Sentence Test, and Dichotic Digit Listening test.

RESULTS: PAM capacity declines in older adults, showing a significant correlation with low-frequency hearing loss. Even older adults with normal hearing exhibit age-related declines. Moreover, reduced PAM was associated with poor binaural processing. A PAM capacity <8 ms effectively identified processing deficits in older adults, indicating compromised temporal processing.

CONCLUSION: Age-related hearing loss influences early-stage binaural cue integration, which is closely associated with deterioration in binaural auditory processing. These findings advance our understanding of direct-to-reverberant sound integration and auditory processing mechanisms in complex acoustic environments.