Timing-dependent modulation of the posterior parietal cortex-primary motor cortex pathway by sensorimotor training

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Science

Background:

• The posterior parietal cortex (PPC) and ipsilateral primary motor cortex (M1) exhibit crucial interplay during movement execution.
• Understanding how sensorimotor training modulates this functional connectivity is key to grasping motor learning mechanisms.

Purpose of the Study:

• To investigate if sensorimotor training can alter functional connectivity between the PPC and M1 in humans.
• To compare the effects of visual versus auditory training modalities on PPC-M1 connectivity.

Main Methods:

• Seventeen participants engaged in a sensorimotor training task involving rhythmic finger tapping.
• Transcranial magnetic stimulation (TMS) assessed PPC-M1 connectivity pre- and post-training, while electroencephalography (EEG) monitored connectivity during training.
• Paired-pulse TMS measured motor-evoked potentials (MEPs) at specific intervals to quantify PPC-M1 facilitation.

Main Results:

• PPC-M1 connectivity showed facilitation before training, which was abolished immediately after but recovered over time.
• EEG revealed increased regional activity and interregional coherence in early training, followed by a decrease in later phases.
• Both visual and auditory training modalities yielded similar patterns of connectivity modulation.

Conclusions:

• Sensorimotor training initially engages PPC-M1 interactions for integrating sensory information into movement plans.
• As movements become automated through training, PPC-M1 connectivity diminishes, returning to baseline levels.
• These findings highlight the dynamic nature of neural plasticity during motor skill acquisition.