Abnormal cortical synaptic plasticity in primary motor area in progressive supranuclear palsy

Area of Science:

• Neuroscience
• Motor Control
• Neuroplasticity

Background:

• Progressive supranuclear palsy (PSP) is a neurodegenerative disease affecting motor function.
• Cortical plasticity in the primary motor area (M1) has not been previously investigated in PSP patients.

Purpose of the Study:

• To investigate M1 cortical plasticity, including long-term potentiation (LTP) and long-term depression (LTD)-like plasticity, in PSP patients.
• To assess changes in M1 plasticity over one year and correlate them with disease progression.

Main Methods:

• Used intermittent theta-burst stimulation (iTBS) for LTP-like plasticity and continuous TBS (cTBS) for LTD-like plasticity in M1.
• Assessed short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), H-reflex, and motor evoked potential (MEP) input-output (I/O) curves.
• Followed 10 patients for one year to re-evaluate iTBS effects.

Main Results:

• PSP patients exhibited significantly greater MEP facilitation after iTBS compared to healthy subjects.
• cTBS, which normally inhibits MEPs, significantly facilitated MEPs in PSP patients.
• PSP patients showed reduced SICI, normal ICF, and steeper MEP I/O slopes, with further increases after iTBS.
• Abnormal MEP facilitation persisted at the 1-year follow-up.

Conclusions:

• Patients with PSP demonstrate abnormal M1 LTP/LTD-like plasticity.
• Enhanced LTP-like cortical synaptic plasticity in M1 is observed in PSP and appears to parallel disease progression.