Modulation of involuntary and voluntary behavior following emotional stimuli in healthy subjects.
Alterations of behavior control are core symptoms of various psychiatric disorders. Patients present with changes in complex behavior patterns and basic motor functions. Little is known about emotional modulation of voluntary behavior. Therefore, a paradigm was developed to study simultaneously influence of emotions on voluntary and involuntary movements. Healthy volunteers (n=30) documented aspects of their mood and personality including depression, anxiety, and impulsivity. Individuals were instructed to view color slides of different emotional content and switch off the slide after by pressing a button, which was placed in a standardized distance from the resting point. The startle reflex was elicited while looking at the slides and quantified by EMG. Kinematic measures of hand movements by infrared detection were used to analyze the patterns of voluntary movements. This study confirmed previous findings about the modulation of the startle reflex by emotional stimuli which may reflect activity of the amygdala and subcortical stimulus processing. Voluntary movements, which may result from cortical processing of stimuli, were not influenced by the emotional context. In individuals with higher impulsivity scores, the startle reflex amplitudes were lower and relative time to peak velocity of the movement smaller. Voluntary movements were not modulated by emotional stimuli, but time to peak velocity was shorter in individuals with greater impulsivity. The ability to generate adequate behavior as a key function of the brain is relevant for social functioning and activities of daily living. The studied paradigm could be useful to assess impulsivity and behavior control in psychiatric disorders.