Low frequency rTMS effects on sensorimotor synchronization

Abstract

Previous studies using low frequency (1 Hz) rTMS over the motor and premotor cortex have examined repetitive movements, but focused either on motor aspects of performance such as movement speed, or on variability of the produced intervals. A novel question is whether TMS affects the synchronization of repetitive movements with an external cue (sensorimotor synchronization). In the present study participants synchronized finger taps with the tones of an auditory metronome. The aim of the study was to examine whether motor and premotor cortical inhibition induced by rTMS affects timing aspects of synchronization performance such as the coupling between the tap and the tone and error correction after a metronome perturbation. Metronome sequences included perturbations corresponding to a change in the duration of a single interval (phase shifts) that were either small and below the threshold for conscious perception (10 ms) or large and perceivable (50 ms). Both premotor and motor cortex stimulation induced inhibition, as reflected in a lengthening of the silent period. Neither motor nor premotor cortex rTMS altered error correction after a phase shift. However, motor cortex stimulation made participants tap closer to the tone, yielding a decrease in tap-tone asynchrony. This provides the first neurophysiological demonstration of a dissociation between error correction and tap-tone asynchrony in sensorimotor synchronization. We discuss the results in terms of current theories of timing and error correction.

Transcranial Magnetic Stimulation in a Finger-tapping Task Separates Motor from Timing Mechanisms and Induces Frequency Doubling

“…The tapping accuracy, as judged by the position of the finger at the time of the metronome click, was slightly improved by TMS at low intensities. Although this is unexpected, it is in line with recent observations of Doumas et al (2005) that motor cortex inhibition decreased the tap-tone asynchrony (tapping inaccuracy).…”

“…Figure 3 displays the percentage of accurate taps for both the unperturbed baseline and for the TMS perturbations (two left columns). TMS does not reduce the accuracy of tapping and, on the contrary, a slight increase is observed (see also Doumas et al, 2005), although the difference is not statistically significant (one tailed t test, p = .15). Interestingly, tapping accuracy remained high also when the finger performed stalls and doubles (see Figure 4, left-most columns).…”

“…This suggests that fast error corrections to the motor function are automatic, occur outside of M1 (Doumas et al, 2005), and do not enter into awareness. On the other hand, the subjects were well aware of the precision with which they were tapping (i.e., of the timekeeper function).…”

“…The advent of transcranial magnetic stimulation (TMS) has enabled a richer approach and resulted in a number of insights on timing (Verstynen et al, 2006;Doumas, Praamstra, & Wing, 2005;Pascual-Leone, Tormos, et al, 1992;Day et al, 1989), trajectory control (Desmurget et al, 1999), stability of motor states (Meyer-Lindenberg, Ziemann, Hajak, Cohen, & Berman, 2002), and motor information processing (Gerloff, Corwell, Chen, Hallett, & Cohen, 1997;Berardelli et al, 1994). The advantage of using TMS for intervention during finger tapping is its relatively localized application in the brain, its temporal precision, and its wide range of output powers.…”

Sensorimotor synchronization: A review of recent research (2006–2012)

“…Doumas, Praamstra, and Wing (2005) found that while disruption of contralateral PMC by rTMS altered neither the NMA nor error correction after a phase shift, disruption of the contralateral motor cortex reduced the magnitude of NMA (i.e., taps fell closer to the tones). The less negative asynchronies as a result of motor cortical inhibition were interpreted as being due to either a slowdown of the timekeeper process, which lengthened the internally measured period, or to a reduced sensitivity of motor cortex to the somatosensory input.…”