Regional cerebellar volumes are related to early musical training and finger tapping performance.

The cerebellum has been associated with timing on the millisecond scale and with musical rhythm and beat processing. Early musical training (before age 7) is associated with enhanced rhythm synchronization performance and differences in cortical motor areas and the corpus callosum. In the present study, we examined the relationships between regional cerebellar volumes, early musical training, and timing performance. We tested adult musicians and non-musicians on a standard finger tapping task, and extracted cerebellar gray and white matter volumes using a novel multi-atlas automatic segmentation pipeline. We found that early-trained musicians had reduced volume in bilateral cerebellar white matter and right lobules IV, V and VI, compared to late-trained musicians. Strikingly, better timing performance, greater musical experience and an earlier age of start of musical training were associated with smaller cerebellar volumes. Better timing performance was specifically associated with smaller volumes of right lobule VI. Collectively, these findings support the sensitivity of the cerebellum to the age of initiation of musical training and suggest that lobule VI plays a role in timing. The smaller cerebellar volumes associated with musical training and timing performance may be a reflection of more efficiently implemented low-level timing and sensorimotor processes.

The role of musical training in emergent and event-based timing.

INTRODUCTION: Musical performance is thought to rely predominantly on event-based timing involving a clock-like neural process and an explicit internal representation of the time interval. Some aspects of musical performance may rely on emergent timing, which is established through the optimization of movement kinematics, and can be maintained without reference to any explicit representation of the time interval. We predicted that musical training would have its largest effect on event-based timing, supporting the dissociability of these timing processes and the dominance of event-based timing in musical performance. MATERIALS AND METHODS: We compared 22 musicians and 17 non-musicians on the prototypical event-based timing task of finger tapping and on the typically emergently timed task of circle drawing. For each task, participants first responded in synchrony with a metronome (Paced) and then responded at the same rate without the metronome (Unpaced). RESULTS: Analyses of the Unpaced phase revealed that non-musicians were more variable in their inter-response intervals for finger tapping compared to circle drawing. Musicians did not differ between the two tasks. Between groups, non-musicians were more variable than musicians for tapping but not for drawing. We were able to show that the differences were due to less timer variability in musicians on the tapping task. Correlational analyses of movement jerk and inter-response interval variability revealed a negative association for tapping and a positive association for drawing in non-musicians only. DISCUSSION: These results suggest that musical training affects temporal variability in tapping but not drawing. Additionally, musicians and non-musicians may be employing different movement strategies to maintain accurate timing in the two tasks. These findings add to our understanding of how musical training affects timing and support the dissociability of event-based and emergent timing modes.

Attentional requirements of walking according to the gait phase and onset of auditory stimuli.

A dual-task paradigm was used to examine the influence of an attention demanding cognitive task on each phase of gait. Twenty-three participants (aged 18-27) walked on a treadmill at a 20% increase of their self-selected speed, either alone or while performing a cognitive task. Muscle activity was measured with electromyography (iEMG) for eight muscles of the dominant leg. The cognitive task consisted of subtracting one (EASY) or seven (HARD) from orally presented numbers. Reaction time (RT) and accuracy were recorded. iEMG events were selected according to stimulus onset (0-150 ms, 150-300 ms and 300-450 ms) prior to phases of gait (double-leg stance, single-leg stance and swing). There was a decrease in iEMG amplitude of fibularis longus (p=.013) and a trend in the same direction for vastus lateralis (p=.065) while walking and performing the cognitive task. When stimulus onset was considered, iEMG of medial gastrocnemius (p=.021) and lateral gastrocnemius (p=.004) were reduced during single-leg stance, when stimuli occurred between 300 and 450 ms prior to this phase. Cognitive performance was affected by task difficulty (RT, accuracy) and by dual-task load (RT). Dual-task costs were observed in both the motor and the cognitive tasks, suggesting that walking requires attention. There was a specific moment (300 ms after stimulus onset) during single-leg stance when dual-task costs were most pronounced, corroborating supraspinal involvement in the control of normal walking. Time-based approaches should be considered when analyzing attentional demands of a dynamic task such as gait.