Matching complex activation patterns with features of natural stimuli
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1
Helsinki University of Technology, Finland
Introduction: Natural stimuli are increasingly used in functional magnetic resonance imaging (fMRI) studies to imitate real-life situations. Consequently, challenges are created for novel analysis methods, including new machine learning tools. With natural stimuli it is no longer feasible to assume single controlled features of the experimental design alone to account for the detectable brain activity. Instead, relevant combinations of rich-enough stimulus features could explain the more complex activation patterns.
Methods: Independent component analysis (ICA) is commonly used in fMRI studies (see, e.g. [1]), in a blind manner, to identify spatially independent patterns of brain activity. With complex stimuli, or complex brain responses, individual components may not be directly relatable to the experimental goals. We propose a novel two-step approach, where ICA is first used to identify spatially independent brain processes, which we refer to as functional patterns. As the second step, temporal dependencies between stimuli and functional patterns are detected using canonical correlation analysis (CCA). Our proposed method looks for combinations of stimulus features and the corresponding combinations of functional patterns.
Results: The two-step approach was used to analyze measurements from a fMRI study during multi-modal stimuli [2]. The detected complex activation patterns were hypothesized to result from interactions of multiple brain processes.
Conclusions: The interpretation of each group of combined patterns should be based on its constituent spatial elements, as well as on relations between the combination's global temporal activity and the stimulus features. Our approach seems promising for analysis of data from studies with natural stimuli.
References
1. J. Ylipaavalniemi and R. Vig?rio: Analyzing Consistency of Independent Components: An fMRI Illustration. NeuroImage 39(1), pp. 169-180
2. J. Ylipaavalniemi, E. Savia, S. Malinen, R. Hari, R. Vig?rio and S. Kaski: Dependencies between stimuli and spatially independent fMRI sources: Towards brain correlates of natural stimuli. Submitted.
Conference:
Neuroinformatics 2008, Stockholm, Sweden, 7 Sep - 9 Sep, 2008.
Presentation Type:
Poster Presentation
Topic:
Neuroimaging
Citation:
Ylipaavalniemi
J and
Vigário
R
(2008). Matching complex activation patterns with features of natural stimuli.
Front. Neuroinform.
Conference Abstract:
Neuroinformatics 2008.
doi: 10.3389/conf.neuro.11.2008.01.067
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Received:
28 Jul 2008;
Published Online:
28 Jul 2008.
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Correspondence:
Jarkko Ylipaavalniemi, Helsinki University of Technology, Helsinki, Finland, jarkko.ylipaavalniemi@tkk.fi