Mohrs Analysis of Brocas Aphasia and Brocas Area

In 1976, Mohr demonstrated that the symptoms classically defined as Broca's aphasia did not correlate with lesions localized in Broca's area proper, BA 44/6; lesions in that area produced transient symptoms similar to those chronic ones associated with much larger lesions. Mohr began by describing the characteristics of the deficit associated with localized lesions of the third frontal convolution, or Broca's area as Broca defined it. Mohr stated the characteristics: Little persisting deficit in articulation seems to occur, and frequently no significant persisting disturbance in language function is present. He based his claims on personal cases of clinical and pathological correlation and an extensive review of cases reported in the literature since 1861 and more than 1 year of cases of stroke documented by Massachusetts area hospitals. Autopsy was the preferred method of analysis of the location of the lesion, but CT scans were also used in a few cases. He formulated a hypothesis of the function of Broca's area that the clinical data support. His current thesis envisions Broca's area as mediating a more traditionally postulated role as a premotor association cortex region concerned with acquired skilled oral, pharyngeal, and respiratory movements involving speaking as well as other behaviors, but not essentially language or graphic behavior per se. Mohr continued by categorizing Broca's aphasia as it was described originally by Broca (as aphemia) and then repeatedly confirmed by others since 1861. The clinical literature continued to rely on Wernicke's 1874 definition that stated three main aspects: Patients are mute, using only a few senseless syllables or swear words with preservation of muscular speech ability; speech comprehension is maintained, but not for complicated constructions; and written language is lost with spoken language. The lesions that produce these symptoms usually involve Broca's area proper, but they are more extensive. Broca's aphasia reflects a major infarction involving most of the territory of supply of the upper division of the left middle cerebral artery. It is observed only after the initial infarction. The initial syndrome is more severe, described traditionally as golobal aphasia. Mohr notes that Broca's original cases involved more extensive lesions;

however, Broca ignored the size and instead relied on the stroke theory of his time, which stated that large strokes always began as a smaller focus and spread slowly outward. Mohr's dissociation of Broca's area proper from the classically defined syndrome of Broca's aphasia suggested that in the clinical literature too much weight was placed on the original classification of the area with the syndrome, and as a result, too broad a range of function had been attributed to the area. Overall, his investigation proved that more detailed analyses would be necessary to determine the finer points of the function of Broca's area proper. Functional imaging technology has brought those details forward, and now experts continue to analyze the area both in clinical populations and with normal subjects.

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