A circuit-based approach to modulate hypersexuality in Parkinson's disease

Area of Science:

• Neuroscience
• Neurology
• Psychiatry

Background:

• Impulse-control disorders (ICDs) are common in Parkinson's disease (PD) patients undergoing dopamine replacement therapy.
• These disorders are hypothesized to stem from an imbalance favoring reward desire over cognitive control.
• Hypersexuality is a prominent ICD in some PD patients.

Purpose of the Study:

• To investigate the neural mechanisms underlying the influence of sexual desire on response inhibition in hypersexual PD patients.
• To explore the potential of neuromodulation for functional restoration in these patients.

Main Methods:

• An erotic stop-signal task assessed the impact of sexual cues on inhibition, with and without dopaminergic medication.
• Functional and anatomical brain connectivity were analyzed in hypersexual PD, nonhypersexual PD, and healthy control groups.
• Intermittent theta-burst stimulation (iTBS) was applied over the pre-supplementary motor area (SMA) in hypersexual PD patients to test its effect on response inhibition.

Main Results:

• Hypersexual PD patients showed distinct brain activation patterns in fronto-striatal and mesolimbic areas (caudate, SMA, VTA, ACC) when medicated.
• Reduced functional connectivity between SMA and caudate nucleus was observed in hypersexual PD patients compared to nonhypersexual PD patients.
• Compensatory enhanced anatomical connectivity was noted in hypersexual PD patients.
• iTBS over the SMA improved response inhibition in hypersexual PD patients when exposed to sexual cues.

Conclusions:

• The study identified a specific fronto-striatal and mesolimbic circuitry associated with uncontrolled sexual responses in medicated PD patients.
• Cortical neuromodulation, specifically iTBS over the SMA, can effectively modulate this circuitry and reduce impulsive behaviors.