Behaviour, physiology and experience of pathological laughing and crying in amyotrophic lateral sclerosis.

Pathological laughing and crying is a disorder of emotional expression seen in a number of neurological diseases. The aetiology is poorly understood, but clinical descriptions suggest a disorder of emotion regulation. The goals of this study were: (i) to characterize the subjective, behavioural and physiological emotional reactions that occur during episodes of pathological laughing and crying; (ii) to compare responses during these episodes to those that occur when emotions are elicited under standard conditions (watching sad and amusing emotional films, being startled); and (iii) to examine the ability of patients with this disorder to regulate their emotions under standardized conditions. Twenty-one patients with pathological laughing and crying due to amyotrophic lateral sclerosis and 14 with amyotrophic lateral sclerosis but no pathological laughing and crying were studied. Emotional measures included self-reported emotional experience, video recordings of facial reactivity and peripheral physiological responses (skin conductance, heart rate and somatic activity). Nineteen of the 21 patients with histories of pathological laughing and crying had at least one episode in the laboratory that they agreed constituted pathological laughing or crying (a total of 56 episodes were documented). Compared with viewing sad and amusing films, the episodes were associated with greater facial and physiological activation. Contrary to many clinical descriptions, episodes were often induced by contextually appropriate stimuli and associated with strong experiences of emotion that were consistent with the display. When instructed to regulate their facial responses to emotion-eliciting films, patients with pathological laughing and crying showed impairments compared with patients who did not have a history of this disorder. These findings support the idea that pathological laughing and crying represents activation of all channels of emotional responding (i.e. behavioural, physiological and subjective). Furthermore, they support previously advanced theories that, rather than being associated with general emotional hyperreactivity, this disorder may be due to dysfunction in frontal neural systems that support voluntary regulation of emotion.