This project will develop and validate a novel approach to modeling fMRI activations in rich experiments with multiple stimuli or tasks. Rather than rely on a spatial correspondence across subjects to identify robust activations, the proposed methods will employ a notion of functional consistency, removing the need to assume spatial alignment among functional areas in different subjects. The resulting models of fMRI activation will also naturally enable studies of anatomical variability in homologous functional regions across subjects. The motivation for this work comes from visual fMRI studies that present subjects with several categories of visual stimuli. As fMRI studies move towards more complex experiments that include more stimuli, the space of possible brain responses grows exponentially, presenting a serious challenge for analysis methods. Explicit representations of fMRI activation patterns that enable exploratory search in the space of possible brain responses are at the core of this project. Computational models of brain activity based on such representations will significantly enrich the utility of fMRI for investigating the functional organization of the brain.
The research team will develop computational methods for fMRI analysis naturally suited for experiments with a multitude of stimuli. The approach is to model the space of all possible activation profiles, to search for stable clusters of activation profiles, and to characterize functionally homogeneous sets of brain locations associated with these clusters. A natural extension of the model will not only identify stable activation profiles but also group stimuli based on the similarity of the evoked activation profiles in the brain. Furthermore, this approach will yield a model of spatial variability of the detected functional areas, leading to better functionally-guided registration algorithms. The methods will be validated in a set of empirical experiments with a large number of visual stimuli in object perception and recognition tasks. The fMRI studies in this project will produce new insights into the functional organization of the ventral pathway of the visual system.
