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

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.

Electrophysiological Activity Associated with a Cross-Modal Anapaest Rhythm: Evidence for the Vestibular Syncopation Hypothesis

“…Can this explain the effect of syncopation, or metrical surprise? This last question was formulated as the vestibular syncopation hypothesis (Todd and Lee 2015a, b;Todd et al, 2022). The current study aims to go some way to answering these questions by applying a cross-modal power analysis of EEG/ECeG in response to a simple rhythmic input.…”

“…The deep cerebellar nuclei project subcortically and also widely to the cerebral cortex, especially frontal areas involved in movement planning and preparation. Thus, the vestibular system could influence rhythm and beat perception via vestibular-cerebellar projections to the frontal cortex (Todd et al, 2021a(Todd et al, , 2022Watson et al, 2014).…”

“…how an anapaest pattern may change from a "Three blind mice" to a "Jingle bells" to a "William Tell" rhythm. The theory also suggested a role for the cerebellum as a feed-forward model in making temporal predictions based on the weighted cortical modulation spectrum (Todd et al, 1999(Todd et al, , 2002, and further, that the central vestibular system was critical as it provided the essential link between sensory and motor representations, including via the vestibular cerebellum (Todd and Lee, 2015a, b;Todd et al, 2022).…”

Electrophysiological Activity Associated With a Cross-Modal Anapaest Rhythm: Evidence for the Vestibular Syncopation Hypothesis

“…The deep cerebellar nuclei project sub-cortically and also widely to the cerebral cortex, especially frontal areas involved in movement planning and preparation. Thus, the vestibular system could in uence rhythm and beat perception via vestibular-cerebellar projections to frontal cortex (Watson, Becker, Apps, & Jones, 2014;Todd, Govender, Lemieux, & Colebatch, 2021a;Todd, Keller, Govender, & Colebatch, 2021c).…”

“…how an anapaest pattern may change from a "Three blind mice" to a "Jingle bells" to a "William Tell" rhythm. The theory also suggested a role for the cerebellum as a feed-forward model in making temporal predictions based on the weighted cortical modulation spectrum (Todd et al, 1999;2002), and further, that the central vestibular system was critical as it provided the essential link between sensory and motor representations, including via the vestibular cerebellum (Todd & Lee, 2015a,b;Todd, Keller, Govender, & Colebatch, 2021c).…”