White matter structural bases for phase accuracy during tapping synchronization

Area of Science:

• Neuroscience
• White Matter Microstructure
• Human Motor Control

Background:

• Rhythmic entrainment, the ability to synchronize movements to external stimuli, is crucial for motor control.
• White matter (WM) integrity, encompassing superficial (SWM) and deep (DWM) tracts, underpins neural communication.
• Understanding the relationship between WM structure and rhythmic synchronization abilities is an emerging area of research.

Purpose of the Study:

• To investigate the association between white matter properties and rhythmic entrainment abilities during a synchronization-continuation tapping task (SCT).
• To explore the role of superficial U-fibers and deep white matter tracts, including the corpus callosum (CC), in auditory and visual synchronization.
• To identify specific white matter microstructural correlates of phase accuracy and preferred tapping tempos.

Main Methods:

• Diffusion-weighted imaging (DWI) was used to assess macro- and microstructural properties of white matter in 32 human subjects.
• Subjects performed the SCT task with auditory or visual metronomes at various tempos (550–950 ms).
• A novel method was employed to quantify the density of short-range U-fibers interconnecting cortical regions.

Main Results:

• Individual differences in U-fiber density within the right audiomotor system correlated with phase accuracy during auditory synchronization, particularly around 1.5 Hz.
• Phase accuracy was also associated with the density and bundle diameter of the corpus callosum (CC).
• The CC showed an interval-selective topography, with anterior regions linked to shorter intervals and posterior regions to longer intervals.

Conclusions:

• Structural properties of both superficial and deep white matter in the audiomotor system are critical for rhythmic tapping synchronization.
• Cortical U-fiber density is linked to an individual's preferred tapping tempo and synchronization precision.
• The corpus callosum's structural characteristics contribute to interval selectivity in rhythmic synchronization tasks.