White matter structural bases for predictive tapping synchronization

Abstract

We determined the intersubject association between rhythmic entrainment abilities of human subjects during a synchronization continuation tapping task (SCT) and the macro and microstructural properties of their superficial (SWM) and deep (dWM) white matter. Diffusion-weighted images were obtained from 32 subjects who also performed the SCT with auditory or visual metronomes and five tempos ranging from 550 to 950 ms. We developed a method to determine the fiber density of U-fibers running tangentially to the cortex. Notably, the right audiomotor system showed individual differences in the density of U-fibers that were correlated with the degree of predictive entrainment across subjects. These correlations were selective for the synchronization epoch with auditory metronomes and were specific for tempos around 1.5 Hz. In addition, there was a significant association between predictive rhythmic entrainment and the density and bundle diameter of the corpus callosum (CC), forming a chronotopic map where behavioural correlations of short and long intervals were found with the anterior and posterior portions of the CC. Finally, the fiber bundle cross-section of the arcuate fasciculus, the CC, and the Superior Longitudinal Fasciculus showed a significant correlation with the mean asynchronies of the auditory SCT. These findings suggest that the structural properties of the SWM and dWM in the audiomotor system support the predictive abilities of subjects during rhythmic tapping, where the density of cortical U-fibers are linked to the preferred tapping tempo, while the bundle properties of CC define an interval selective topography that has an anterior posterior gradient.

Rhythmic tapping to a moving beat: motion kinematics overrules motion naturalness

“…The temporal variability is a measure of timing precision and corresponds to the standard deviation of the produced intervals. Asynchronies are the time differences between stimuli and tap responses, and represent measures of rhythmic prediction, which can be evaluated only during the synchronization epoch of SCT (Merchant et al, 2008b; Gámez et al, 2018; García-Saldivar et al, 2022).…”

“…Classical tapping studies coined the notion of preferred rhythmic tempo, which corresponds to the interval produced naturally when asked to tap in the absence of external cues (Fraisse, 1963(Fraisse, , 1978McAuley et al, 2006). The preferred tempo in human adults is around 600ms (García-Saldivar et al, 2022). The present findings indicate that, during the last three intervals of the continuation epoch, the subjects' indifference interval converged to a particular value that was shorter for flashing than accelerating and decelerating metronomes and was larger for non-natural than natural gravity motion (Figure 2).…”

“…The temporal variability is a measure of timing precision and corresponds to the standard deviation of the produced intervals. Asynchronies are the time differences between stimuli and tap responses, and represent measures of rhythmic prediction, which can be evaluated only during the synchronization epoch of SCT (Merchant et al, 2008b;Gámez et al, 2018;García-Saldivar et al, 2022). (C) 𝑠𝑇𝑉 as a function of 𝑐𝑇𝑉 for all serial order elements for the flashing metronomes (blue), all directions with accelerated (red +) and all directions with decelerated (green-) motion.…”

“…We defined two measures to characterize this behavior using a linear regression on this data: the intercept at 650 ms (𝑐𝐶𝐸), and the slope of the regression called 𝑠𝐶𝐸 (Figure 2E). The former is proportional to the indifference interval, namely, the interval where there is no error in timing (McAuley and Jones, 2003;Rajendran et al, 2018;García-Saldivar et al, 2022). The latter corresponds to the magnitude of the bias effect, i.e., the larger the negative slope, the larger the regression towards the mean (Jazayeri and Shadlen, 2010;Petzschner et al, 2015;Perez and Merchant, 2018).…”

“…Similarly, we regressed the constant error on the 𝑡 𝑑 and defined two other measures to characterize further the SCT behavior (see Figure 2E): 1) the intercept at 650 ms (𝑐𝐶𝐸), which is proportional to the indifference interval, namely, the interval where there is no error in timing (McAuley and Jones, 2003;Rajendran et al, 2018;García-Saldivar et al, 2022);…”