Aging effects on neural processing of rhythm and meter

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.

Aging impacts basic auditory and timing processes

“…These results are consistent with the enhanced event-related responses described earlier and support the notion of heightened excitability or reduced inhibition of the auditory cortex in aging 19 . However, the increase in OSc at the Sf contrasts with prior evidence showing diminished encoding of temporal regularity in metronome-like auditory sequences obtained through typical Fourier analyses 26,27 .…”

“…This observation is consistent with the enhanced event-related responses described earlier and supports the notion of heightened excitability (or reduced inhibition) of the auditory cortex in aging [20]. While prior evidence showed diminished encoding of temporal regularity in metronome-like auditory sequences (obtained through typical Fourier analyses) [29,30], the removal of the fractal component from the frequency spectrum allowed revealing the reversed pattern: enhanced evoked responses to sounds in older individuals. This result seems to confirm prior evidence showing greater neural synchronization with sounds modulations in aging individuals, and an increased sensitivity to temporal regularities [17,22,24,31].…”

“…There is consensus in associating these larger ERP responses with the reduced ability to employ ‘sensory gating’ 22 , an adaptive mechanism to suppress cortical responses to repetitions of predictable stimuli 20,23 . Furthermore, variability in the latency of event-related responses to sounds 21,25 and the reduction in steady-state responses to auditory metronomes 26,27 suggest a change in encoding the precise timing of sensory events, and internalizing the temporal regularity in auditory sequences. These observations suggest that aging may impact the capacities to detect regularities in the sensory environment, generate predictions about future events, and employ these predictions to inform sensory processing and perception.…”

Neural Entrainment to Musical Pulse in Naturalistic Music Is Preserved in Aging: Implications for Music-Based Interventions

“…While music has been shown to entrain neural activity, impairments in neural entrainment to musical features are associated with aging [ 13 , 44 , 45 , 46 , 47 , 48 , 49 ]. Relatedly, several neurodegenerative disorders, such as Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD), are associated with disrupted neural activity across the same frequency bands that are driven by music (e.g., delta, theta) [ 50 , 51 , 52 , 53 ].…”

“…Secondly, we predicted that neural responses to the pulse would be relatively stronger at fronto–central electrodes, reflecting synchronized neural activity to music arising from the auditory system [ 34 , 70 , 71 ]. Finally, we expected younger adults to exhibit stronger neural entrainment to the musical pulse, compared to older adults, given that degraded neural responses to sound are often associated with aging [ 45 , 48 ].…”