ABSTRACT
When listening to musical rhythm, humans can perceive and move to beat-like metrical pulses. Recently, it has been hypothesized that meter perception is related to brain activity responding to the acoustic fluctuation of the rhythmic input, with selective enhancement of the brain response elicited at meter-related frequencies. In the current study, electroencephalography (EEG) was recorded while younger (<35) and older (>60) adults listened to rhythmic patterns presented at two different tempi while intermittently performing a tapping task. Despite significant hearing loss compared to younger adults, older adults showed preserved brain activity to the rhythms. However, age effects were observed in the distribution of amplitude across frequencies. Specifically, in contrast with younger adults, older adults showed relatively larger amplitude at the frequency corresponding to the rate of individual events making up the rhythms as compared to lower meter-related frequencies. This difference is compatible with larger N1-P2 potentials as generally observed in older adults in response to acoustic onsets, irrespective of meter perception. These larger low-level responses to sounds have been linked to processes by which age-related hearing loss would be compensated by cortical sensory mechanisms. Importantly, this low-level effect would be associated here with relatively reduced neural activity at lower frequencies corresponding to higher-level metrical grouping of the acoustic events, as compared to younger adults.
ABSTRACT
In music, entrainment to the beat allows listeners to make predictions about upcoming events. Previous work has shown that neural oscillations will entrain to the beat of the music or rhythmic stimuli. Despite the fact that aging is known to impact both auditory and cognitive processing, little is known about how aging affects neural entrainment to rhythmic stimuli. In this study, younger and older participants listened to isochronous sequences at a slower and faster rate while EEG data was recorded. Steady-state evoked potentials had amplitude peaks at the stimulus rate and its harmonics. Steady-state evoked potentials at the stimulus rate and the first harmonic was attenuated in older adults compared to younger adults. Additionally, no amplitude difference was found for the second and third harmonics in older adults, while there was a decrease in amplitude in younger adults. This age-related decline in the entrainment specificity of the brain responses to the stimulus rate, suggests that aging may decrease the ability to entrain to stimuli in the environment, and further suggests that older adults may be less able to inhibit neural entrainment that is not directly related to the incoming stimulus.
