In quest of an internal timekeeper: contribution to the understanding of how the brain deals with rhythmical behaviours

Abstract

The main objective of the present work was to contribute to the understanding of how the brain deals with rhythmical behaviours, as the title says. The line of approach was to investigate the cerebral correlates of tempo production, using a new and a seldom used behavioural paradigm. The new paradigm consisted of regular and irregular sensorimotor synchronisation (SMS) tasks. Both conditions implied duration estimation, feedback and error correction. Only the regular condition induced an internal rhythm. The seldom used paradigm consisted of self-paced finger tapping tasks at spontaneous motor tempo and other tempi. The use of strictly self-paced tapping made it possible to avoid contaminating the production by any previously heard tempo. Subtraction of selfpaced related brain activation patterns from synchronisation patterns was done in order to isolate the brain mechanisms of synchronisation. Subtracting synchronisation brain activation patterns during irregular finger tapping from those during regular finger tapping conditions was used to isolate cerebral activity involved in the production of isochronous finger tapping. The results suggest that duration estimation and internal timekeeping require similar brain regions. These seem to be involved mainly in duration estimation and retention, and error correction. It is proposed that the signals sent by the body during rhythmical tasks play a role in the processing of an internal pulsation. It is also suggested that internal timekeeping imply the generation of an internal model of the external stimuli or of the rhythmic pattern to produce. This role could be assumed by the network composed of the basal ganglia and supplementary motor area (Grahn, 2009).