Nov 20, 2015

Mind the drift - improving sensitivity to fMRI pattern information by accounting for temporal pattern drift

BioRxiv : the Preprint Server for Biology
Arjen AlinkNikolaus Kriegeskorte

Abstract

Analyzing functional magnetic resonance imaging (fMRI) pattern similarity is becoming increasingly popular because it allows one to relate distributed patterns of voxel activity to continuous perceptual and cognitive states of the human brain. Here we show that fMRI pattern similarity estimates are severely affected by temporal pattern drifts in fMRI data - even after voxel-wise detrending. For this particular dataset, the drift effect obscures orientation information as measured by fMRI pattern dissimilarities. We demonstrate that orientation information can be recovered using three different methods: 1. Regressing out the drift component through linear modeling; 2. Computing representational distances between conditions measured in independent imaging runs; 3. Crossvalidation of pattern distance estimates. One possible source of temporal pattern drift could be random walk like fluctuations - physiological or scanner related - occurring within single voxel timecourses. This explanation is consistent with voxel-wise detrending not alleviating pattern drift effects. In addition, this would explain why cross-validated pattern distances are robust to temporal drift because a random walk process is expected to give rise to non-repl...Continue Reading

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Mentioned in this Paper

Study
Fluctuation
Patterns
Magnetic Resonance Imaging
Brain
Cross Validation
FMRI
Disease Regression
Perception
Cognition

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