Effects of Stimulus Intensity and Frequency on the Force and Timing of Sensorimotor Synchronisation

Neil P M Todd,Sendhil Govender,James G Colebatch,Peter E Keller

doi:10.1163/22134468-bja10041

Abstract

Abstract We report an experiment to investigate possible vestibular effects on finger tapping to an auditory anapaest rhythm. In a sample of 10 subjects, index finger acceleration and tapping force were recorded along with extensor/flexor activity and the associated electroencephalographic activity measured at central and cerebellar surface electrodes. In a prior session with a standard short air-conducted 500-Hz pip, vestibular evoked myogenic potential thresholds were measured and subsequently used to set the acoustic intensity. During the main experiment subjects were asked to synchronise tapping to the pips arranged in the anapaest at two different frequencies, 500 Hz vs 5 kHz, so that only the low-frequency high-intensity condition was a vestibular, as well as an auditory stimulus. We hypothesised that a vestibular effect would manifest in an interaction between the frequency and intensity factors for a range of dependent measures of tapping performance. No clear evidence was found for vestibular effects, but this was likely due to the confounding effects of an independent effect of intensity and the relative weakness of the acoustic vestibular stimulus. However, the data did show novel evidence for two distinct timing processes for the flexion and extension stages of a tap cycle and two distinct timing strategies, which we refer to as ‘staccato’ and ‘legato’, characterised by different profiles of force and extension.

Highlights

Sensorimotor synchronisation in the form of finger tapping to a regular auditory metronome is a well-established paradigm to investigate mechanisms of human motor timing (Repp, 2005; Repp & Su, 2013)
In our own recent work we have shown that short-latency vestibular cerebellar evoked potentials (VsCEPs) and an associated spontaneous electrocerebellogram (ECeG) can be recorded over the posterior fossa in response to stimuli that activate vestibular evoked myogenic potentials, including 500 Hz air- and bone-conducted sound as well as impulsive head accelerations (Govender et al, 2020; Todd et al, 2017, 2018a, b, 2019)
In a sample of 10 subjects the flexor/extensor activity and associated acceleration and contact force were recorded during synchronised finger tapping to an anapaest auditory rhythm along with S1/M1 EEG, ECeG and extra-ocular EMG

Summary

Introduction

Sensorimotor synchronisation in the form of finger tapping to a regular auditory metronome is a well-established paradigm to investigate mechanisms of human motor timing (Repp, 2005; Repp & Su, 2013). Lewis and Miall (2003) refer to ‘automatically’ and ‘cognitively’ controlled systems, while Teki et al (2011) distinguish ‘duration-based’ and ‘beat-based’ auditory timing, Grahn and Rowe (2013) ‘beat detection’ and ‘beat prediction’ systems, and Todd and Lee (2015a, 2015b) two systems for ‘externally’ vs ‘internally’ guided action involving the cerebellum and basal ganglia. There has in the last decade or so been an increasing awareness of a contribution of the vestibular system to timing, with suggestions that it may play an important role in synchronisation, especially with regards to the beat (Phillips-Silver & Trainor, 2005, 2007, 2008; Trainor et al, 2009). The matter remains controversial, with some authors suggesting that the vestibular influence is not direct (Riggle, 2009; Trainor, 2007; Trainor & Unrau, 2009)

Methods

Results

Conclusion