Brodmanns Description of Brocas Area

In 1909, Korbinian Brodmann published a treatise, "Localization in the Cerebral Cortex,'' on histological localization in the cerebral cortex. He described his work in the introduction: "Localization which uses exclusively anatomical features as the basis for investigation, in contrast to physiological or clinical aspects'' (as quoted in Garey, 1994, p. 117). The lasting result of this work was a scheme for the parcellation of the cerebral cortex into 50 distinct areas based on common anatomical features. The system is still used as a standard for cortical localization.

Broca's area was designated by Brodmann as area 44: ''a well-differentiated and sharply circumscribed structural region that on the whole corresponds quite well to the opercular part of the inferior frontal gyrus: Broca's area'' (as quoted in Garey, 1994, p. 117). Brodmann defined the anatomical boundaries of area 44 as the inferior precentral sulcus posteriorly, the inferior frontal sulcus superiorly, and the ascending ramus of the Sylvian fissure anteriorly, but he amended his description: ''As there is much variability and inconstancy of these sulci one will find rather mixed topographical relationships of these structural areas in individual cases'' (as quoted in Garey, 1994, p. 117).

In addition, Brodmann found enough similarity in the structure of area 44 to that of two other nearby areas, 45 and 47, that he grouped them into a subregion, the ''subfrontal subregion.'' A fourth area, 46, was also more loosely grouped with 44, 45, and 47 in the frontal region, and Brodmann said it was not distinguishable from surrounding areas by its cell structure. These areas are considered to be subdivisions of the more general Broca's area addressed in functional imaging literature today. Brodmann's identification of a cytoarchitectonic area matching the placement of Broca's ''third frontal convolution'' was a confirmation from yet another scientific discipline to add to Broca's own and subsequent clinical and physiological evidence.

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