Functional imaging: Heterogeneity in task strategy and functional anatomy and the case for individual analysis

To learn more about the functional anatomy of language, the authors used [T c-99m]HMPAO single photon emission computed tomography (SPECT) functional i maging to study nonword rhyming, lexical-semantics and syntax. The authors did not find any task-related differences in cerebral blood flow using regi on-by-region analysis of variance. This led them to examine individual subj ect's task-related patterns of cerebral blood flow. This analysis revealed regions of interest with little or no change but also regions with changes as great as 30%. There was marked subject-to-subject variability in the pat tern of blood flow, which precluded statistically significant results using analysis of variance. An alternative analytic strategy based on numbers of subjects exceeding a minimum threshold task-related change in cerebral blo od flow was tested and shows promise in identifying commonalities and diffe rences in individual task-related blood flow patterns. The authors conclude that the complex and difficult to interpret pattern of blood flow changes observed in this study reflect in considerable part the combined effects of variability in task strategy, owing in part to insufficiently constrained task performance, and variability in functional anatomy. The authors also t ested the differences in results achieved with simple normalization and ana lysis of covariance approaches and found them to be insignificant.