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PLoS One. 2017 Aug 4;12(8):e0182657. doi: 10.1371/journal.pone.0182657. eCollection 2017.

Multivariate Bayesian decoding of single-trial event-related fMRI responses for memory retrieval of voluntary actions.

Lee D1,2, Yun S3, Jang C3, Park HJ2,3,4,5.

Author information

1
Faculty of Psychology and Education Sciences, University of Coimbra, Coimbra, Portugal.
2
Center for Systems and Translational Brain Sciences, Institute of Human Complexity and Systems Science, Yonsei University, Seoul, Republic of Korea.
3
BK21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea.
4
Department of Nuclear Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea.
5
Department of Cognitive Science, Yonsei University, Seoul, Republic of Korea.

Abstract

This study proposes a method for classifying event-related fMRI responses in a specialized setting of many known but few unknown stimuli presented in a rapid event-related design. Compared to block design fMRI signals, classification of the response to a single or a few stimulus trial(s) is not a trivial problem due to contamination by preceding events as well as the low signal-to-noise ratio. To overcome such problems, we proposed a single trial-based classification method of rapid event-related fMRI signals utilizing sparse multivariate Bayesian decoding of spatio-temporal fMRI responses. We applied the proposed method to classification of memory retrieval processes for two different classes of episodic memories: a voluntarily conducted experience and a passive experience induced by watching a video of others' actions. A cross-validation showed higher classification performance of the proposed method compared to that of a support vector machine or of a classifier based on the general linear model. Evaluation of classification performances for one, two, and three stimuli from the same class and a correlation analysis between classification accuracy and target stimulus positions among trials suggest that presenting two target stimuli at longer inter-stimulus intervals is optimal in the design of classification experiments to identify the target stimuli. The proposed method for decoding subject-specific memory retrieval of voluntary behavior using fMRI would be useful in forensic applications in a natural environment, where many known trials can be extracted from a simulation of everyday tasks and few target stimuli from a crime scene.

PMID:
28777830
PMCID:
PMC5544208
DOI:
10.1371/journal.pone.0182657
[Indexed for MEDLINE]
Free PMC Article

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