Modulation of intra- and inter-hemispheric connectivity between primary and premotor cortex during speech perception

Area of Science:

• Neuroscience
• Auditory Perception
• Motor Control

Background:

• Primary motor (M1) areas activate during speech perception.
• Premotor cortex (PMv) may modulate M1 activity.
• The precise role of PMv in speech perception, especially under challenging conditions, is unclear.

Purpose of the Study:

• To investigate the link between PMv and M1 during challenging speech perception.
• To determine how PMv differentially modulates M1 activity during clear versus distorted speech comprehension.

Main Methods:

• Two experiments using transcranial magnetic stimulation (TMS) on PMv and M1.
• Experiment 1: Continuous theta burst stimulation (cTBS) on left PMv and motor evoked potentials (MEPs) in left M1 lip area.
• Experiment 2: Dual-coil TMS on right PMv and left M1 lip area.

Main Results:

• Disrupting PMv specifically affected comprehension of distorted speech.
• Distorted speech perception modulated intra- and inter-hemispheric interactions between PMv and M1.
• A larger sensorimotor network was implicated in distorted speech comprehension compared to clear speech.

Conclusions:

• PMv plays a critical role in processing challenging speech.
• Auditory-motor integration involves complex PMv-M1 interactions.
• These findings advance understanding of neural mechanisms underlying speech perception.