Non-linear Relationship between BOLD Activation and Amplitude of Beta Oscillations in the Supplementary Motor Area during Rhythmic Finger Tapping and Internal Timing

Abstract

Functional imaging studies using BOLD contrasts have consistently reported activation of the supplementary motor area (SMA) both during motor and internal timing tasks. Opposing findings, however, have been shown for the modulation of beta oscillations in the SMA. While movement suppresses beta oscillations in the SMA, motor and non-motor tasks that rely on internal timing increase the amplitude of beta oscillations in the SMA. These independent observations suggest that the relationship between beta oscillations and BOLD activation is more complex than previously thought. Here we set out to investigate this rapport by examining beta oscillations in the SMA during movement with varying degrees of internal timing demands. In a simultaneous EEG-fMRI experiment, 20 healthy right-handed subjects performed an auditory-paced finger-tapping task. Internal timing was operationalized by including conditions with taps on every fourth auditory beat, which necessitates generation of a slow internal rhythm, while tapping to every auditory beat reflected simple auditory-motor synchronization. In the SMA, BOLD activity increased and power in both the low and the high beta band decreased expectedly during each condition compared to baseline. Internal timing was associated with a reduced desynchronization of low beta oscillations compared to conditions without internal timing demands. In parallel with this relative beta power increase, internal timing activated the SMA more strongly in terms of BOLD. This documents a task-dependent non-linear relationship between BOLD and beta-oscillations in the SMA. We discuss different roles of beta synchronization and desynchronization in active processing within the same cortical region.

Differential contributions of the two human cerebral hemispheres to action timing

“…Condition differences were stronger in the low compared to the high beta band in the SMA and in the right A2 (SMA: t(16) = 3.033, p=0.002, p=0.818, right A2: t(16) = 1.907, p=0.046), but not in the left A2 (left A2: t(16) = 0.228), a region that did not show condition effects in the fMRI. This confirms a more pronounced role of the low compared to the high beta band in rhythm generation (Gompf et al, 2017; Fujioka et al, 2015). Further analyses were therefore focused on the low beta band.…”

“…To reveal directed connectivity when representing two rhythms instead of one rhythm, we focused the connectivity analyses on the contrast between slow and fast tapping and restricted them again to the low beta band (Gompf et al, 2017; Fujioka et al, 2015).…”

“…A functional lateralization in terms of differences in activation of functional homologues was only observed in the auditory and not in the motor association cortices. Together with the cerebellum, motor cortices rather mirrored the actual motor output with a stronger BOLD signal in the bilateral SMA associated with reduced beta suppression during internal timing compared to auditory-motor synchronization (Gompf et al, 2017). Beta suppression during slow tapping was not maximal such that ceiling levels cannot explain missing lateralization in the SMA.…”

Low-Frequency Oscillations Code Speech during Verbal Working Memory

“…2). Increased amplitudes of beta oscillations have been associated with internal timing processes during sequencing (Gompf et al, 2017). We hypothesize that relatively higher amplitudes of beta oscillations during sentence encoding facilitate phase separation and thus enhance the memory representation contained therein.…”

Differential contributions of the two cerebral hemispheres to temporal and spectral speech feedback control

“…Spectral adaptation also increased connectivity between L aSTS and L IPS and between R pSTS and HG ( auditory association cortex connected more strongly with the left SMA following temporal perturbations. The SMA has been implicated in action timing and in processing temporal aspects of sensory input [34][35][36][37][38] . We thus propose the SMA as an additional motor-to-auditory interface that internally translates the temporal structure of articulator actions into expected auditory consequences.…”