Brodmann area 45

Brodmann area 45 (BA45), is part of the frontal cortex in the human brain. It is situated on the lateral surface, inferior to BA9 and adjacent to BA46. This area in humans occupies the triangular part of inferior frontal gyrus (H) and, surrounding the anterior horizontal limb of the lateral sulcus (H), a portion of the orbital part of the inferior frontal gyrus (H). Bounded caudally by the anterior ascending limb of the lateral sulcus (H), it borders on the insula in the depth of the lateral sulcus. In terms of cytoarchitecture, it is bounded caudally by the opercular part of inferior frontal gyrus (Brodmann area 44 (BA44)), rostrodorsally by the middle frontal area 46 (BA46), and ventrally by the orbital part of inferior frontal gyrus (Brodmann area 47 BA47). The left-hemisphere Brodmann area 44 and Brodmann area 45 make up Broca's area, a region that is active in semantic tasks, such as semantic decision tasks (determining whether a word represents an abstract or a concrete entity) and generation tasks (generating a verb associated with a noun). The precise role of BA45 in semantic tasks remains controversial. For some researchers, its role would be to subserve semantic retrieval or semantic working memory processes. Under this view, BA44 and BA45 would together guide recovery of semantic information and evaluate the recovered information with regard to the criterion appropriate to a given context. A slightly modified account of this view is that activation of BA45 is needed only under controlled semantic retrieval, when strong stimulus-stimulus associations are absent. For other researchers, BA45's role is not restricted to semantics per se, but to all activities that require task-relevant representations from among competing representations. Lesions of the BA45 lead to the characteristic findings of expressive aphasia in individuals who are left hemispheric dominant. A strong correlation has been found between speech-language and the anatomically asymmetric pars triangularis. Foundas, et al.