damage to this part of the brain can result in reduced ability to comprehend and/or produce humor
Right hemisphere brain damage For the majority of the nineteenth century, the left brain hemisphere was the key focus of clinical research on language disorders (Brookshire, 2007).[2] In the twentieth century, focus gradually shifted to include right hemisphere damage (Brookshire, 2007).[2] It is now well established that language and cognition can be seriously impaired by unilateral right hemisphere brain damage.[40] Specific cognitive tests can help diagnose the existence of right hemisphere brain damage and differentiate symptoms from those of left hemisphere damage.[41] Unlike the aphasias, caused by left hemisphere damage and generally resulting in focused language deficits, right hemisphere brain damage can result in a variety of diffuse deficits which complicate formal testing of this disorder (Brookshire, 2007).[2] These formal tests assess areas such as understanding humor, metaphors, sarcasm, facial expression, and prosody.[23] However, not all individuals with right hemisphere brain damage have problems in language or communication and some may have no discernible symptoms.[40] Indeed, about half of patients with right hemisphere damage have intact communication abilities (Brookshire, 2007).[2][42]
Broca's area In the classical sense, expressive aphasia is the result of injury to Broca's area; it is often the case that lesions in specific brain areas cause specific, dissociable symptoms,[27] although case studies show there is not always a one-to-one mapping between lesion location and aphasic symptoms.[24] The correlation between damage to certain specific brain areas (usually in the left hemisphere) and the development of specific types of aphasia makes it possible to deduce (albeit very roughly) the location of a suspected brain lesion based only on the presence (and severity) of a certain type of aphasia, though this is complicated by the possibility that a patient may have damage to a number of brain areas and may exhibit symptoms of more than one type of aphasia. The examination of lesion data in order to deduce which brain areas are essential in the normal functioning of certain aspects of cognition is called the deficit-lesion method; this method is especially important in the branch of neuroscience known as aphasiology. Cognitive science - to be specific, cognitive neuropsychology - are branches of neuroscience that also make extensive use of the deficit-lesion method.[28]