Supplementary motor area contributions to rhythm perception

Abstract

Timing is everything, but our understanding of the neural mechanisms of timing remains limited, particularly for timing of sequences. Temporal sequences can be represented relative to a recurrent beat (beat-based or relative timing), or as a series of absolute durations (non-beat-based or absolute timing). Neuroimaging work suggests involvement of the basal ganglia, supplementary motor area (SMA), the premotor cortices, and the cerebellum in both beat- and non-beat-based timing. Here we examined how beat-based timing and non-beat-based sequence timing were affected by modulating excitability of the supplementary motor area, the right cerebellum, and the bilateral dorsal premotor cortices, using transcranial direct current stimulation (tDCS). Participants were subjected to a sham stimulation session, followed an active stimulation session where anodal or cathodal 2mA tDCS was applied to the SMA, right premotor cortex, left premotor cortex, or the cerebellum. During both sessions, participants discriminated changes in rhythms which differentially engage beat-based or non-beat-based timing. Rhythm discrimination performance was improved by increasing SMA excitability, and impaired by decreasing SMA excitability. This polarity-dependent effect on rhythm discrimination was absent for cerebellar or premotor cortex stimulation, suggesting a crucial role of the SMA and/or its functionally connected networks in rhythmic timing mechanisms.

Investigating the Causal Role of Motor Brain Areas in Rhythm Reproduction: A Transcranial Direct Current Stimulation Study

“…Beat perception can be measured by different tasks and functions and taken together with the results of tDCS in the SMA during rhythm discriminationthe effects of stimulation may be too weak to be observed during reproduction. Similarly, effects of stimulation on rhythm discrimination were seen for the cerebellum (Leow et al, 2022), but not during reproduction here. The different roles of motor brain regions in rhythm perception and production therefore may be easier to observe with tDCS when more sensory, rather than sensorimotor, tasks are used.…”

“…For the cerebellum, both anodal and cathodal stimulation worsened discrimination performance. These results indicate that both the SMA and cerebellum play roles in rhythm discrimination, but, they do not support a selective role of the SMA role in beat-based timing, as stimulation affected discrimination of both strong- and weak-beat rhythms (Leow et al, 2022). Further, the cerebellar stimulation had a selective effect on strong-beat rhythm discrimination, counter to its proposed role in absolute, not relative (beat-based) timing.…”

“…A previous study using strong- and weak-beat rhythms demonstrated the SMA’s crucial role in rhythm discrimination using tDCS (Leow et al, 2022). During anodal stimulation of the SMA, participants discriminated rhythm changes more accurately than during sham stimulation, and during cathodal stimulation, participants discriminated more poorly than during sham.…”

“…Despite extensive research using correlational neuroimaging methods (Grahn & Brett, 2007; Grahn & Rowe, 2009; Teki et al, 2011), and neuropsychological studies (Breska & Ivry, 2018; Grahn & Brett, 2009), few studies have used causal methods in healthy humans (Leow et al, 2022). Transcranial direct current stimulation (tDCS) is one way to causally examine the role of different brain areas in different timing processes.…”

Fundamental Sensory and Motor Neural Control in the Brain for the Musical Performance

“…In summary, recent neuroimaging topics were introduced. Among them, SMA seems to be involved in the function of beat-based timing, expression and activity of musical behavior [21]. Research on music, MT, and piano performance from empirical, theoretical, and practical perspectives has been developed [22].…”