Mechanisms of rhythm perception : effect of tempo on neural and behavioral response to musical rhythm

Details

Supervisors

Verleysen, Michel ; Nozaradan, Sylvie

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil biomédical, à finalité spécialisée

Abstract

Humans have a natural ability to perceive beat and meter in rhythm. This ability is possibledue to several complex and diverse neural networks, extending from the vestibular systemto cortical elaboration. Hypothesis: perception of beat and meter can be induced by audio sequences composed of periodic pulses (as a metronome), but can also be induced complex rhythms. It seems that humans have a preferential range of perception and expression of the meter and beat. The movement is correlated to the rhythm and its expression (dance, tapping with the hands, ...) and seems correlated with the perception of the meter and beat. Finally, on the EEG response, there is a link between the frequencies related to the perception of the meter andan enhancement of these same frequencies on the EEG spectrum. Question: this study is interested in the modification of features related to the EEG response and related to the perception of the meter to the presentation of an audio sequence composed of a complex rhythm when tempo is changing. The change of tempo is slight. We present here the setting up of an experiment studying rhythms, the relevance of certain parameters and metrics used in the analysis of these first results. Material and methods: the experiment is using frequency tagging, consisting of study in the frequency domain a periodic stimulus using EEG. The stimulus used is an audio stimulus composed of a complex rhythm, using 3 slight tempo variations. This constitutes the listening trial. A behavioral task assess the perception of the beat and meter by tapping on a box according to his perception of the meter. This exploits the mapping between the perception of rhythm and movement. This constitutes the tapping trial. A computer pipeline is developed to analyze these data, a focus is done on the interoperability using the latest tools for data management and for EEG data analysis. Results: this first analysis is performed on a sample of 12 participants. The results of the tapping trial show a variation of the tapping behavior, this distribution does not vary according to the tempo. The number of people who failed the task does not vary following the tempo. EEG analysis shows difference in the spectrum energy distribution between the presented auditory stimulus spectrum at the frequencies of interest derived from frequency tagging and EEG response. The Z score related to the perception of the meter are compared and does not vary across tempi. Discussion: the project is a first end-to-end approach to an experiment studying rhythm. It aims to understand the different difficulties of the development of an experiment in neuroscience. Solutions are proposed in response to difficulties and are either tested here or discussed and will be implemented in a more advanced version of the experiment. The results of the EEG response and tapping corroborate to the observations from previous studies, the detailed study of slight variation of tempo requires a larger cohort in order to be able to uncover any hypotheses and confirm certain intuitions. These preliminary results show no variation of perception across tempi neither by looking the behavioral task (tapping task) nor by analysing the Z score meter related (EEG record). This support the robustness of meter perception when the tempo stay in an human range hypothesis. There is no major shift in the perception of the beat and the meter when changing the tempo.