Dopaminergic Degeneration Differentially Modulates Primary Motor Cortex Activity and Motor Behavior in...

Area of Science:

• Neuroscience
• Motor Control
• Neurodegenerative Diseases

Background:

• Parkinson's disease (PD) impairs dopaminergic transmission, affecting motor cortex (M1) activity and causing motor deficits.
• The precise M1 response to dopaminergic degeneration and levodopa treatment is not fully understood.

Purpose of the Study:

• To investigate M1 neuronal activity and motor behavior in hemiparkinsonian rats.
• To characterize changes during naïve, lesioned, and levodopa-treated states using in vivo calcium imaging.

Main Methods:

• Unilateral 6-hydroxydopamine (6-OHDA) lesioning in Sprague Dawley rats.
• In vivo calcium imaging of M1 using GCaMP6f and GRIN lenses.
• Longitudinal assessment of motor behavior (single pellet reaching test) and M1 calcium activity (event frequency and influx).

Main Results:

• Levodopa treatment significantly improved fine motor skills, reducing grasp errors and increasing reaching duration.
• M1 calcium activity modulated with lesion severity: reduced frequency and increased influx in low-lesion rats post-lesion; increased influx in high-lesion rats post-levodopa.
• Calcium influx, not frequency, negatively correlated with lesion severity during levodopa treatment.

Conclusions:

• M1 neuronal activity is differentially modulated by dopaminergic degeneration and levodopa treatment, depending on lesion severity.
• These findings highlight dynamic cortical responses in Parkinson's disease.
• In vivo calcium imaging is a valuable tool for monitoring circuit-level changes in PD and its treatment.