Traditional period perturbations in sensorimotor synchronization confound experimental manipulations

Abstract: Paced finger tapping is a sensorimotor synchronization task where a subject has to keep pace with a metronome and the time differences (asynchronies) between each stimulus and its response are recorded. A usual way to study the underlying error correction mechanism is to perform unexpected temporal perturbations to the stimuli sequence. An overlooked issue is that at the moment of a temporal perturbation two things change: both the stimuli period (a parameter) and the asynchrony (a variable). In terms of experimental manipulation, it would be desirable to have separate, independent control of parameter and variable values. In this work we perform paced finger tapping experiments combining simple temporal perturbations (tempo step change) and spatial perturbations with temporal effect (raised or lowered point of contact). In this way we decouple the parameter-and-variable confounding, performing novel perturbations where either the parameter or the variable changes. Our results show nonlinear features like asymmetry and are compatible with a common error correction mechanism for all types of asynchronies. We suggest taking this confounding into account when analyzing perturbations of any kind in finger tapping tasks but also in other areas of sensorimotor synchronization, like music performance experiments and paced walking in gait coordination studies.

Short bio: Rodrigo Laje has a Ph.D. in Physics and conducts research on how the brain tells time. His theoretical/experimental group is focused on the hundred millisecond timing range where human sensorimotor synchronization occurs. He is also the current president of Expedicion Ciencia, a non-profit NGO devoted to science outreach and science education.