Individual functional anatomy of verb generation.

Examination of the individual functional anatomy of language is of particular interest in clinical neurology to explain the variability of aphasic symptoms after focal lesions and to avoid damage of language-related brain areas by surgery. For a silent verb generation task, we examined whether activation PET with 3D data acquisition, multiple replication of conditions, and coregistration with MRI provides results that are consistent and reproducible enough to be useful clinically. Visual analysis was performed on PET-MRI fusion images, including renderings of the brain surface. Quantitative analysis was based on volumes of interest. In seven right-handed normals, activation of the triangular part of the left inferior frontal cortex [Brodman area (BA) 45] was the most significant finding that was present in each subject. Two subjects showed minor anatomical variants of the ascending or horizontal ramus of the sylvian fissure that were associated with the least activation of BA 45. In the left hemisphere the other frontal gyri, the superior temporal and posterior part of the middle temporal gyrus, and the paracingulate gyrus were also significantly activated. There was significant bilateral cerebellar activation, but it was significantly more intense on the right than on the left side. The consistency and high interindividual reproducibility of these findings suggest that this technique may be useful for clinical assessment of language-related areas.