[Are Interlimb Interactions Disturbed in Patients with Parkinson's Disease: a Study in Unloading Condition?]

Area of Science:

• Neuroscience
• Human Locomotion
• Movement Disorders

Background:

• Natural human locomotion involves neural connections for quadrupedal walking.
• Interactions between upper and lower limb neural networks are modulated by brain motor commands.
• Parkinson's disease (PD) distorts these commands, potentially impairing interlimb coordination.

Purpose of the Study:

• To investigate interlimb interactions during cyclic movements in patients with Parkinson's disease (PD) and healthy controls.
• To assess the influence of arm movements on leg movements and vice versa under unloaded conditions.
• To examine the effect of medication on interlimb coordination in PD patients.

Main Methods:

• Studied 17 patients with PD and 16 healthy subjects under unloaded arm and leg conditions.
• Assessed the effect of limb movement in one girdle on the motor activity of the other girdle during combined cyclic movements.
• Investigated involuntary air-stepping activation via vibratory stimulation and the influence of arm movements.

Main Results:

• Patients with PD exhibited weakened influence of arm movements (active/passive, distal) on voluntary leg movements compared to significant effects in healthy subjects.
• The facilitating effect of arm movements on involuntary leg stepping activation was absent in PD patients.
• Differences were observed in the influence of leg movements on upper extremity rhythmic movement between PD patients and controls.
• Medication showed some interlimb interaction but did not normalize neural network activity in PD patients.

Conclusions:

• Neural networks generating stepping rhythm in PD patients are in a state of heightened tonic activity.
• This heightened activity prevents involuntary rhythmic movement activation and hinders facilitatory arm-to-leg effects.
• PD significantly impairs interlimb coordination, suggesting a need for targeted therapeutic strategies.