Readiness potentials recorded from the scalp and depth leads.

Area of Science:

• Neuroscience
• Motor Control
• Electrophysiology

Background:

• Readiness potentials (RPs) are slow negative shifts in brain electrical activity preceding voluntary movements.
• Understanding RP generation is crucial for deciphering motor control mechanisms.
• Disruptions in RPs are observed in various neurological disorders.

Purpose of the Study:

• To investigate the characteristics of readiness potentials during voluntary hand movements.
• To compare RP parameters between healthy subjects and patients with involuntary movement disorders, specifically parkinsonism.
• To explore the spatio-temporal dynamics of RPs in different brain regions, including scalp, cortex, white matter, and thalamus.

Main Methods:

• Recorded scalp (C3, C4), premotor cortex, subcortical white matter, and thalamic VL nucleus readiness potentials.
• Utilized healthy right-handed men and patients diagnosed with involuntary movement disorders (parkinsonism).
• Analyzed the onset time (mean T) and amplitude of readiness potentials relative to motor activity.

Main Results:

• A slow negative shift preceding voluntary hand movements was observed in scalp and cortical recordings.
• Healthy men exhibited mean T values of 0.8s (right hand) and 1.0s (left hand).
• Parkinsonian patients showed prolonged mean T values (1.4s with akinesia, 1.1s without akinesia). RP amplitude was higher contralaterally. Cortical RPs preceded VL nucleus RPs by ~0.1s, with reversed polarity in subcortical regions.

Conclusions:

• Readiness potential timing and amplitude are altered in parkinsonism, reflecting motor control deficits.
• RPs originate earlier in the cortex than in the thalamus (VL nucleus).
• RPs exhibit distinct polarity characteristics across different brain regions, including scalp, cortex, white matter, and thalamus.