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the right posterior middle temporal gyrus and the cerebellum.
Cerebral activity in the medial ventral prefrontal cortex
Studies of humour in normal subjects covaried with the subject's post-scan ratings of joke funniness
In a study of cortical electrical activity associated with and, thus, may have been associated with the affective
humour information processing, Derks and colleagues appreciation of humour.
reported a peak of activity in event-related potentials In both of these studies, the perception of (joke-induced)
(ERPs) ~300 ms after hearing the punch-line of a joke humour was associated with blood oxygen level-dependent
(Derks et al., 1997). This was followed by a general activity in the temporal regions and in the left frontal areas,
depolarization ~100 ms later. These two waves were but the areas in the two studies did not exactly match and
suggested to parallel the two-stage cognitive model of areas of activity were described in the second study that were
humour processing (Suls, 1972; Forabosco, 1992). The not described in the ®rst. Neither study included controls for
results of this study also suggested that mood could in¯uence such confounding variables as attention or emotional facial
humour processing: positive mood, compared with negative reactions; thus, the presumption that humour was a cause of
mood, was accompanied by greater differences in ERPs the observed activations may be premature.
between jokes producing laughter and those producing no Using PET, Iwase and colleagues studied subjects' facial
laughter. In a more recent study using ERPs, however, reactions to humorous ®lm clips (Iwase et al., 2002). During
Coulson and Kutas (2001) were unable to differentiate humour-induced smiling or laughter (measured by EMG of
between the elements of surprise and the subsequent coher- facial muscles), a selective increase in regional cerebral blood
ence stage in healthy subjects as they read sentences, the last ¯ow (rCBF), compared with baseline, was found bilaterally in
word of which made them either jokes or not. Although these the subjects' supplementary motor areas (SMAs) and the left
two elements could not be shown to differ between the jokes putamen. Humour-associated laughter/smiling, as opposed to
and the non-jokes, the ERPs did differ in several respects voluntary smiling, was associated with increased rCBF in the
depending on whether the subjects were good or poor visual association areas, left anterior temporal cortex, left
comprehenders of jokes. uncus and orbitofrontal and medial prefrontal cortices,
In two recent studies, functional MRI was used to whereas voluntary smiling was associated with increased
demonstrate areas of blood oxygen level-dependent cerebral rCBF in the face area of the left primary motor cortex and
activity in normal subjects as they listened to jokes. In the ®rst bilateral SMA when compared with humorous smiling. In this
of these (Ozawa et al., 2000), 10 subjects listened to a tape paradigm, however, it was impossible to distinguish between
recording of three different genres of texts from within a rCBF related to the presence of humour and that related to the
functional MRI apparatus: jokes, a simple newspaper article, behavioural reactions.
and a complicated philosophical text. Later, the subjects In a study of facial reactions to pictures of faces expressing
ranked the individual texts with respect to how funny each emotions (Wild et al., 2003), activation of both basal
text was and how dif®cult each had been to understand. temporal cortices, including the amygdalae, was observed
Consistent with the linguistic nature of the tasks, Wernicke's when subjects generated smiles in response to pictures of
area and the transverse temporal gyri (bilaterally) were smiling faces.
2134 B. Wild et al.
To summarize the results on humour and the brain, there is of humour (slapstick, ironic, aggressive, self effacing, etc.)
convincing evidence from studies of patients with brain have common neural networks? Do the stages of appreciating
lesions that the non-dominant hemisphere is necessary for the a joke involve discrete brain regions?
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