Abnormal affective startle modulation in individuals with psychogenical movement disorder

Abstract

Despite recent advances, psychogenic movement disorder (PMD) remains a poorly understood phenomenon. Emotional functioning and responsiveness to stress are believed to play a role in the development of psychogenic symptoms, but empirical studies examining emotional responsiveness in PMD and other conversion disorders are lacking. We investigated modulation of the startle eyeblink reflex by affective pictures in 12 patients with PMD and 12 age- and education-matched control participants. Participants viewed positive, neutral, and negative pictures, while eyeblink responses to white noise bursts were recorded. Control participants showed the expected pattern of startle modulation, with significant potentiation by negative pictures and slight (nonsignificant) inhibition by positive pictures. In the PMD group, however, both positive and negative pictures yielded significantly greater startle responses than neutral pictures. Depression and anxiety symptomatology did not correlate with startle modulation, and the two groups did not differ in self-reported emotional reactions to the pictures. Our findings suggest that individuals with PMD show aversive physiological reactions to positive as well as negative stimuli. Abnormal affective startle modulation may be used to help distinguish between malingering and PMD. Future studies using larger samples are needed to better understand the role of emotions in conversion disorder.

Aversive stimuli exacerbate defensive motor behaviour in motor conversion disorder

“…Moreover, maximum force and force immediately prior to image onset was not different between groups. In agreement with previous reports (Kanaan, et al, 2007;Seignourel, et al, 2007), a decoupling between affective experience and behavioural reactivity may reflect the non-volitional nature of FND, where modulation of emotion and motor processing occur outside conscious awareness (Blakemore, et al, 2013(Blakemore, et al, , 2015. A dissociation between affective experience and emotion-motor Fig.…”

“…These results may be due to higher states of emotional arousal associated with FND (Horvath, et al, 1980;Lader and Sartorius, 1968). Exaggerated startle reflex responses to arousing images in conversion patients (Seignourel, et al, 2007) is consistent with this notion. In line with this, Bakvis and colleagues (2010) demonstrated patients with psychogenic non-epileptic seizures have higher levels of baseline cortisol, indicative of higher stress state.…”

“…Seignourel et al (2007) found normal potentiation of the startle eyeblink response (a protective reflex following abrupt stimuli) following unpleasant stimuli in FND, but potentiated responses following pleasant stimuli, rather than startle inhibition as seen in controls, indicating aversive physiological reactivity to both negative and positive emotions in these patients. Other studies point to a general arousing effect, where patients have shown increased amygdala activity to fearful and happy faces compared to neutral faces (Voon et al, 2010a), a failure to habituate skin conductance to acoustic stimuli and higher baseline arousal levels (Lader and Sartorius, 1968), and increased levels of baseline cortisol (Bakvis, et al, 2010).…”

“…Rather, patients showed a loss of valence-specific effects in IFG and mPFC, as these areas responded to general arousal, with similarly enhanced activation to pleasant and unpleasant stimuli. Although this remains speculative without direct comparisons against a neutral emotion condition, this notion would accord with general arousing effects (Seignourel et al, 2007;Voon et al, 2010a).…”

“…A selective effect of negative emotions in our study is therefore inconsistent with a general effect of arousal in FND. However, none of the previous studies (e.g., Seignourel, et al, 2007;Voon et al, 2010a) investigated the effect of arousal on voluntary motor output, but instead focussed on passive exposure conditions. It is possible that differences in emotional valence emerge only when concurrent affective processing and volitional motor control are required.…”