Functional localization of brain activity in the Iowa Gambling Task using graph theoretical methods
Functional connectivity methods, particularly graph theory methods, are an area of growing interest for researchers interested in network based neuroimaging approaches. This study attempted to offer another useful extension of graph theoretical approaches to functional neuroimaging. In particular, the neuroimaging study of the Iowa Gambling Task (IGT) Several task related brain regions have been found during IGT performance using standard subtraction based neuroimaging paradigms. However, the identification of a proper baseline for the IGT has complicated the study of task related activations in the IGT. In this study, two graph theory methods are offered as an alternative method of functional localization without traditional subtraction assumptions. These methods rely on the consistency of functional groupings of brain areas across time to identify areas in the brain specialized for particular cognitive functions, without the need for a baseline comparison. They are applied to a within subject fMRI data set consisting of 8 healthy young adults at rest, and performing the IGT and a simple spatial orienting task. Both methods localized areas in the visual and sensorimotor cortices. Unexpectedly, the Scaled Inclusivity method localized areas of the DMN across both task states in addition to rest. However, permutation tests of the SI maps revealed significant differences in the spatial extent of DMN consistency across all three tasks. The future application of both methods for functional localization, and the functional significance of the DMN during the IGT and other task states are discussed.