Paired-Pulse Parietal-Motor Stimulation Differentially Modulates Corticospinal Excitability across Hemispheres When...

Area of Science:

• Neuroscience
• Cognitive Science
• Neurophysiology

Background:

• Leftward prism adaptation (LPA) induces neglect-like symptoms in healthy individuals.
• Repetitive transcranial magnetic stimulation (rTMS) on the posterior parietal cortex (PPC) affects neglect symptoms and parietal-motor (PPC-M1) connectivity.
• An analogy suggests LPA may modulate PPC-M1 excitability differently between hemispheres.

Purpose of the Study:

• To investigate the hypothesis that LPA differentially affects left and right hemisphere PPC-M1 excitability.
• To elucidate the neurophysiological mechanisms underlying LPA's cognitive effects.

Main Methods:

• Healthy participants underwent leftward prism adaptation (LPA).
• Dual-site paired-pulse transcranial magnetic stimulation (ppTMS) was used to measure PPC-M1 excitability.
• Motor evoked potentials (MEPs) in the primary motor cortex (M1) were recorded.

Main Results:

• LPA led to increased MEP amplitude in the left M1 and decreased amplitude in the right M1.
• These changes were observed for both paired and single ppTMS pulses.
• A control experiment confirmed that LPA alone did not affect M1 input-output curves.

Conclusions:

• LPA differentially alters the excitability of the left and right M1.
• The findings suggest LPA may bias interhemispheric connectivity.
• This provides insights into the neural basis of prism adaptation effects on motor control and spatial attention.