Abnormal affective startle modulation in individuals with psychogenical movement disorder

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. (c) 2007 Movement Disorder Society