This centre would be capable of coordinating the faciorespiratory functions associated with laughter and crying. It has been hypothesized that PLC is caused by a loss of voluntary inhibition of a presumed centre for laughter and crying located in the upper brainstem ( Wilson, 1924). ![]() In a related condition, the so-called `fou rire prodromique' ( Féré, 1903), pathological laughing is a transient manifestation that heralds a brainstem stroke involving the basis pontis or the cerebral peduncles ( Wali, 1993). In a review of autopsy findings in 30 patients, PLC was never correlated with a single cortical lesion, but the internal capsule was damaged in all patients ( Poeck, 1985). PLC has also been noted in association with cerebrovascular lesions involving the descending corticobulbar pathways, most notably at the level of internal capsule, the cerebral peduncles and the basis pontis ( Black, 1982 Poeck, 1985 Bassetti et al., 1996 Kim, 1997 Kim and Choi-Kwon, 2000). PLC has been noted in gelastic epilepsy ( Arroyo et al., 1993), multiple sclerosis ( Feinstein et al., 1997), pseudobulbar palsy ( Black, 1982) and tumours in the cerebellopontine region ( Achari and Colover, 1976). the facial expressions, the tears, etc.) is identical in PLC, in mood disorders and in the normal condition. However, the essence of the actual laughter or crying behaviours (e.g. It is distinguishable from the mood disorders in which laughter and crying are associated with feelings of happiness or sadness, and from regular laughter or crying in which the emotional expression is consonant with the triggering stimulus. PLC is a disorder of emotional expression rather than a primary disturbance of feelings. For example, patients can laugh in response to sad news or cry in response to a moving hand in the visual field, and the expression of laughter can abruptly change to crying ( Poeck, 1985). ![]() In some instances, the stimulus may have an emotional valence contrary to the emotional expression. The episodes either do not have an apparent motivating stimulus or are triggered by a stimulus that would not have led the subject to laugh or cry prior to the onset of the condition. Pathological laughter and crying (PLC) is a condition defined by relatively uncontrollable episodes of laughter, crying or both. PLC = pathological laughter and crying, SSRI = selective serotonin reuptake inhibitor, TOH = Tower of Hanoi task Introduction Here we suggest that the critical PLC lesions occur in the cerebro-ponto-cerebellar pathways and that, as a consequence, the cerebellar structures that automatically adjust the execution of laughter or crying to the cognitive and situational context of a potential stimulus, operate on the basis of incomplete information about that context, resulting in inadequate and even chaotic behaviour. 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 alternative. ![]() ![]() In that view, the lesions `disinhibit' or `release' the laughter and crying centre. The 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 descend to the brainstem to inhibit a putative centre for laughter and crying. 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. The episodes occur either without an apparent triggering stimulus or following a stimulus that would not have led the subject to laugh or cry prior to the onset of the condition. Patients with pathological laughter and crying (PLC) are subject to relatively uncontrollable episodes of laughter, crying or both.
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