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Bayesian Classification of FMRI Data: Evidence for Altered Neural Networks in Dementia

The alterations in functional relationships among brain regions associated with senile dementia are not well understood. We present a machine learning technique using dynamic Bayesian networks (DBNs) that extracts causal relationships from functional magnetic resonance imaging (fMRI) data. Based on these relationships, we build neural-anatomical networks that are used to classify patient data as belonging to healthy or demented subjects. Visual-motor reaction time task data from healthy young, healthy elderly, and demented elderly patients (Buckner et al. 2000) was obtained through the fMRI Data Center. To reduce the extremely large volume of data acquired and the high level of noise inherent in fMRI data, we averaged data over neuroanatomical regions of interest. The DBNs were able to correctly discriminate young vs. elderly subjects with 80% accuracy, and demented vs. healthy elderly subjects with 73% accuracy. In addition, the DBNs identified causal neural networks present in 93% of the healthy elderly studied. The classification efficacy of the DBN was similar to two other widely used machine learning classification techniques: support vector machines (SVMs) and Gaussian naïve Bayesian networks (GNBNs), with the important advantage that the DBNs provides candidate neural anatomical networks associated with dementia. Networks found in demented but not healthy elderly patients included substantial involvement of the amygdala, which may be related to the anxiety and Burge et al., Page 2 agitation associated with dementia. DBNs may ultimately provide a biomarker for dementia in its early stages, and may be helpful for the diagnosis and treatment of other CNS disorders.