Causal interhemispheric neuromodulation sharpens synaptic and neurobehavioral inhibition in stroke

Area of Science:

• Neuroscience
• Neuroimaging
• Neurophysiology

Background:

• Hemispheric functional asymmetries are crucial for brain organization.
• Understanding hemispheric (im)balance plasticity is vital for neurological disorders like stroke.
• Interhemispheric inhibition via transcranial magnetic stimulation is a key stroke treatment.

Purpose of the Study:

• To investigate the neurobehavioral and neurochemical effects of cortical stimulation on hemispheric balance.
• To explore how GABA regulation (pre- and post-synaptic) changes with hemispheric stimulation in stroke.
• To elucidate the mechanism of action for transcranial magnetic stimulation in stroke recovery.

Main Methods:

• Utilized a multimodal brain imaging and stimulation setup.
• Conducted molecular imaging sessions measuring GABA receptor levels with sham and real neurostimulation.
• Performed functional magnetic resonance imaging (fMRI) and GABA neurospectroscopy.

Main Results:

• Noninvasive neuromodulation sharpened pre- and post-synaptic GABA neurotransmitter and receptor levels.
• A positive association between GABA neurotransmitter and receptor levels indicated increased synaptic coupling.
• Correlated reduction in pre- and post-synaptic variability demonstrated a plasticity mechanism.

Conclusions:

• Inhibitory neuromodulation offers a mechanism for stabilizing synapses and rebalancing brain activity.
• This plasticity mechanism is fundamental to long-range inhibitory hemispheric interactions.
• Findings provide insights into transcranial magnetic stimulation protocols for stroke and hemispheric imbalance disorders.