Friday, Sep 11, 2015
Effects of age, noise and hearing loss on concurrent sound segregation
1Rotman Research Institute at Baycrest Centre, Toronto, Canada
2Department of Biophysics, Radboud University Nijmegen, Germany
Our ability to perceptually organize sounds that occur simultaneously is paramount to solving the cocktail party problem. In a series of experiments, we examined the effects of age, noise and hearing loss on listeners’ ability to separate concurrent sounds using frequency periodicity. We measured auditory evoked fields (AEFs) using magnetoencephalography while participants were presented with complex tones that had either all harmonics in tune or had the third harmonic mistuned by 4 or 16% of its original value. The harmonic complex tones (75 dB sound pressure level, SPL) were presented without, with low (45 dBA SPL), or with moderate (65 dBA SPL) Gaussian noise. For each participant, we modeled the AEFs with a pair of dipoles in the superior temporal plane. We then examined the effects of hearing loss and noise on the amplitude and latency of the resulting source waveforms. The results revealed an age-related increase in P1m amplitude and similar noise-induced changes in auditory responses of older adults with and without hearing loss. Our results also showed that the P1m amplitude was larger in the hearing impaired than in the normal-hearing adults. In addition, the object-related negativity (ORN) elicited by the mistuned harmonic was modulated by age and hearing loss. The changes in P1m and ORN amplitude in the hearing impaired older adults suggests that hearing loss increased neural excitability in auditory cortices, which could be related to deficits in inhibitory control.