Inhibitory framing in hypersexual patients with Parkinson's disease. An fMRI pilot study

Abstract

Hypersexuality in medicated patients with PD is caused by an increased influence of motivational drive areas and a decreased influence of inhibitory control areas due to dopaminergic medication. In this pilot study, we test a newly developed paradigm investigating the influence of dopaminergic medication on brain activation elicited by sexual pictures with and without inhibitory contextual framing. Twenty PD patients with and without hypersexuality were examined with fMRI either OFF or ON standardized dopaminergic medication. The paradigm consisted of a priming phase where either a neutral context or an inhibitory context was presented. This priming phase was either followed by a sexual or a neutral target. Sexual, compared to neutral pictures resulted in a BOLD activation of various brain regions implicated in sexual processing. Hypersexual PD patients showed increased activity compared to PD controls in these regions. There was no relevant effect of medication between the two groups. The inhibitory context elicited less activation in inhibition-related areas in hypersexual PD, but had no influence on the perception of sexual cues. The paradigm partially worked: reactivity of motivational brain areas to sexual cues was increased in hypersexual PD and inhibitory contextual framing lead to decreased activation of inhibitory control areas in PD. We could not find a medication effect and the length of the inhibitory stimulus was not optimal to suppress reactivity to sexual cues. Our data provide new insights into the mechanisms of hypersexuality and warrant a replication with a greater cohort and an optimized stimulus length in the future.

Keywords: Addiction; Dopamine; Functional MRI; Impulse control.

Fig. 1

A Paradigm structure—Four, five or six consecutive pictures of either healthy skin (neutral context) or of infectious skin (inhibitory context) were followed by a sexual target or a neutral control target. Both were masked with a scrambled version. Each context–target combination was shown ten times per session and participants watched three sessions. B Timing of one paradigm block. During the context priming skin pictures were shown for 2 s each. In eight blocks of each session, one of the skin pictures was replaced with a book (attention check). The target was displayed for 150 ms and followed by a mask (350 ms). The jittered pause lasted on average 2500 ms

Fig. 2

Functional MRI results A Brain regions with increased activity in sexual versus control pictures (contrast for the whole sample, including all conditions), B increase activation in PD+HS relative to PD-HS when seeing sexual targets in comparison to control cues, C the bars represent increased activation during inhibitory context (H-) relative to non-inhibitory context (H+) for the peak voxels of the two significant clusters in the left medial frontal gyrus (left panel) and left superior frontal gyrus (right panel). H + neutral context, H- Inhibitory context, HS+ Hypersexual patients, HS- non-hypersexual patients, OFF/ON is referring to medication status, PD Parkinson’s disease. Color bars represent t-value