Auditory filter width affects response magnitude but not frequency specificity in auditory cortex.

Spectral analysis of acoustic stimuli occurs in the auditory periphery (termed frequency selectivity) as well as at the level of auditory cortex (termed frequency specificity). Frequency selectivity is commonly investigated using an auditory filter model, while frequency specificity is often investigated as neural adaptation of the N1 response in electroencephalography (EEG). However, the effects of aging on frequency-specific adaptation, and the link between peripheral frequency selectivity and neural frequency specificity have not received much attention. Here, normal hearing younger (20-31 years) and older participants (49-63 years) underwent a psychophysical notched noise experiment to estimate individual auditory filters, and an EEG experiment to investigate frequency-specific adaptation in auditory cortex. The shape of auditory filters was comparable between age groups, and thus shows intact frequency selectivity in normal aging. In auditory cortex, both groups showed N1 frequency-specific neural adaptation effects that similarly varied with the spectral variance in the stimulation, while N1 responses were overall larger for older than younger participants. Importantly, the overall N1 amplitude, but not frequency-specific neural adaptation was correlated with the pass-band of the auditory filter. Thus, the current findings show a dissociation of peripheral frequency selectivity and neural frequency specificity, but suggest that widened auditory filters are compensated for by a response gain in frequency-specific areas of auditory cortex.