Serotonergic cortico-limbic and executive network dysfunction in Parkinson's disease impulse control disorders: a...

Area of Science:

• Neuroscience
• Neurology
• Psychiatry

Background:

• Impulse control disorders (ICDs) affect up to 45% of Parkinson's disease (PD) patients.
• The neural mechanisms underlying ICDs in PD remain poorly understood.
• Understanding these mechanisms is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the neural pathways and neurochemical underpinnings of ICDs in Parkinson's disease.
• To identify specific brain connectivity alterations associated with ICDs in PD patients.
• To explore the role of serotonergic dysfunction in the development of ICDs in PD.

Main Methods:

• Multimodal neuroimaging: Positron Emission Tomography (PET) and resting-state functional Magnetic Resonance Imaging (fMRI).
• Study population: 23 PD patients (11 with ICDs, 12 without) and 14 healthy controls.
• Behavioral assessments: Delay discounting tasks to measure decision-making and impulsivity.

Main Results:

• PD patients with ICDs (PD-ICD+) exhibited steeper delay discounting compared to PD patients without ICDs (PD-ICD-) and controls.
• Altered functional connectivity was observed in PD-ICD+ patients, including enhanced posterior parietal coupling within executive networks and disrupted salience-executive interactions.
• Aberrant connectivity between the right supplementary motor area (SMA) and the amygdala was significantly linked to ICD severity and decisional impulsivity.
• Increased SMA 5-HT₂ₐ receptor availability correlated with enhanced SMA-amygdala coupling, which in turn was associated with ICD symptoms.

Conclusions:

• Serotonergic dysfunction, specifically involving 5-HT₂ₐ receptors in the SMA, contributes to disrupted motor-limbic network connectivity in PD patients with ICDs.
• These neurobiological alterations provide a mechanistic link between serotonergic dysfunction, aberrant brain connectivity, and impulsive behavior in Parkinson's disease.
• Identifying these targetable pathways offers potential therapeutic strategies for managing ICDs, a common non-motor complication of PD.