(185), Max Planck Institute for Biological Cybernetics, Tübingen, Germany, May 2009 (techreport)
Kernel Canonical Correlation Analysis is a very general technique for subspace learning that incorporates
PCA and LDA as special cases. Functional magnetic resonance imaging (fMRI) acquired data is naturally
amenable to these techniques as data are well aligned. fMRI data of the human brain is a particularly interesting
candidate. In this study we implemented various supervised and semi-supervised versions of KCCA on human
fMRI data, with regression to single- and multi-variate labels (corresponding to video content subjects viewed
during the image acquisition). In each variate condition, the semi-supervised variants of KCCA performed better
than the supervised variants, including a supervised variant with Laplacian regularization. We additionally analyze
the weights learned by the regression in order to infer brain regions that are important to different types of visual
In Advances in Neural Information Processing Systems 22, pages: 126-134, (Editors: Bengio, Y. , D. Schuurmans, J. Lafferty, C. Williams, A. Culotta), Curran, Red Hook, NY, USA, 23rd Annual Conference on Neural Information Processing Systems (NIPS), 2009 (inproceedings)
Resting state activity is brain activation that arises in the absence of any task, and is usually measured in awake subjects during prolonged fMRI scanning sessions where the only instruction given is to close the eyes and do nothing. It has been recognized in recent years that resting state activity is implicated in a wide variety of brain function. While certain networks of brain areas have different levels
of activation at rest and during a task, there is nevertheless significant similarity between activations in the two cases. This suggests that recordings of resting
state activity can be used as a source of unlabeled data to augment discriminative regression techniques in a semi-supervised setting. We evaluate this setting
empirically yielding three main results: (i) regression tends to be improved by the use of Laplacian regularization even when no additional unlabeled data are available, (ii) resting state data seem to have a similar marginal distribution to that recorded during the execution of a visual processing task implying largely similar types of activation, and (iii) this source of information can be broadly exploited to improve the robustness of empirical inference in fMRI studies, an inherently data poor domain.
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