Dynamic discrimination analysis: A spatial–temporal SVM

• Published in: NeuroImage (Orlando, Fla.) Vol. 36; no. 1; pp. 88 - 99
• Main Authors: Mourão-Miranda, Janaina, Friston, Karl J., Brammer, Michael
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.05.2007; Elsevier Limited
• Subjects: Adult; Affect - physiology; Algorithms; Arousal - physiology; Artificial Intelligence; Brain Mapping; Cerebral Cortex - physiology; Classifiers; Discrimination; Dominance, Cerebral - physiology; Dynamic analysis; Electroencephalography; Functional magnetic resonance imaging data analysis; Humans; Image Enhancement; Image Processing, Computer-Assisted; Machine learning methods; Magnetic Resonance Imaging; Male; Mathematical Computing; Medical imaging; NMR; Nuclear magnetic resonance; Oxygen - blood; Pattern recognition; Pattern Recognition, Visual - physiology; Signal Processing, Computer-Assisted; Studies; Support vector machine; Classifiers; Support vector machine; Functional magnetic resonance imaging data analysis; Machine learning methods; Dynamic analysis
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2007.02.020

Recently, pattern recognition methods (e.g., support vector machines (SVM)) have been used to analyze fMRI data. In these applications the fMRI scans are treated as spatial patterns and statistical learning methods are used to identify statistical properties of the data that discriminate between brain states (e.g., task 1 vs. task 2) or group of subjects (e.g., patients and controls). We propose an extension of these approaches using temporal embedding. This makes the dynamic aspect of fMRI time series an explicit part of the classification. The proposed pattern recognition approach uses both spatial and temporal information. Temporal embedding was implemented by defining spatiotemporal fMRI observations and applying a support vector machine to these temporally extended observations. This produces a discriminating weight vector encompassing both voxels and time. The resulting vector furnishes discriminating responses, at each voxel without imposing any constraints on their temporal form.