Written by members of the Wellcome Department of Imaging Neuroscience
Friston KJ, Frith CD, Fletcher P, Liddle PF, Frackowiak RSJ (1996)
Cerebral Cortex In press
In neuroimaging functional mapping usually implies mapping function into an anatomical space, for example using statistical parametric mapping to identify activation foci, or the characterization of distributed changes with spatial modes (eigenimages or principal components) (Friston et al 1993a). This article is about a complementary approach; namely mapping anatomy into a functional space. We describe a simple variant of multidimensional scaling (principal coordinates analysis Gower 1966) that uses functional connectivity as its metric. The scaling transformation maps anatomy into a functional space. The topography, or proximity relationships, in this space embody the functional connectivity among brain regions. The higher the functional connectivity the closer the regions. Functional connectivity is defined here as the correlation between remote neurophysiological events. The technique represents a descriptive characterization of anatomically distributed changes in the brain that reveals the structure of cortico-cortical interactions in terms of functional correlations. To illustrate the approach we have analyzed data from normal subjects and schizophrenic patients obtained with PET during the performance of word generation tasks. In particular we focus on prefronto-temporal integration in normal subjects and show that, in schizophrenia, the left temporal regions and prefrontal cortex evidence abnormal functional connectivity.
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