Age-related changes in neural trace generation of rule-based auditory features.

Young (M = 22) and elderly volunteers (M = 74) participated in an ERP study that examined rule-based feature ion in the auditory modality. Stimuli were either a frequent ascending tone pair or an infrequent descending tone pair. Tone-pairs were presented under three conditions. Physical feature monaural (1 tone pair), feature monaural (10 tone pairs), and feature binaural (10 tone pairs). Volunteers watched a silent movie during ERP recordings. After completion of the ERP session all volunteers participated in a behavioral discrimination task. MMNs were elicited under all three conditions for the young. For the elderly, MMNs were elicited under both monaural conditions but not under binaural conditions. Behavioral discrimination was high under the physical feature condition but fell to near chance under the two rule-based feature conditions for both age groups. Thus rule-based neural representations were generated for both age groups under monaural conditions, but only for the young under binaural conditions, suggesting that there is an age-related decline in the efficacy of integrating multiple sources into a single auditory stream.