Pathological laughter and crying - A link to cerebellum

Patients with pathological laughter and crying (PLC) are subject to relativ ely uncontrollable episodes of laughter, crying or both. The episodes occur either without an apparent triggering stimulus or following a stimulus tha t would not have led the subject to laugh or cry prior to the onset of the condition. PLC is a disorder of emotional expression rather than a primary disturbance of feelings, and is thus distinct from mood disorders in which laughter and crying are associated with feelings of happiness or sadness. T he traditional and currently accepted view is that PLC is due to the damage of pathways that arise in the motor areas of the cerebral cortex and desce nd to the brainstem to inhibit a putative centre for laughter and crying. I n that view, the lesions 'disinhibit' or 'release' the laughter and crying centre. The neuroanatomical findings in a recently studied patient with PLC , along with new knowledge on the neurobiology of emotion and feeling, gave us an opportunity to revisit the traditional view and propose an alternati ve. Here we suggest that the critical PLC lesions occur in the cerebro-pont ocerebellar pathways and that, as a consequence, the cerebellar structures that automatically adjust the execution of laughter or crying to the cognit ive and situational context of a potential stimulus, operate on the basis o f incomplete information about that context, resulting in inadequate and ev en chaotic behaviour.