Pathological laughter and crying

The classic literature on pathological laughter and crying emphasizes the difference between incontinence and lability of affect. Pathological laughter and crying as key symptoms of affect incontinence are viewed as the effects of disinhibition of motor synergisms without congruent affect, which is the crucial difference to affect lability. The interpretation as a disinhibitory phenomenon is supported by clinical and electromyographic observations, which found a lack of modulation of intensity in pathological laughter and crying. In 1924, Wilson postulated a supranuclear pontobulbar center for affective synergisms that is controlled by cortex and thalamus. Accordingly, Kleist viewed a combined lesion of thalamic or brainstem structures and corticofugal motor projection systems as the pathoanatomic basis of affect incontinence. Recent work reported the frequent occurrence of affect incontinence with stroke and dementia of the Alzheimer type and thus disagrees with the classical theory. However, the methods used cannot rule out a confounding between affect lability and incontinence.