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Published February 11, 2015 | Published
Journal Article Open

Single-Unit Recordings in the Macaque Face Patch System Reveal Limitations of fMRI MVPA


Multivariate pattern analysis (MVPA) of fMRI data has become an important technique for cognitive neuroscientists in recent years; however, the relationship between fMRI MVPA and the underlying neural population activity remains unexamined. Here, we performed MVPA of fMRI data and single-unit data in the same species, the macaque monkey. Facial recognition in the macaque is subserved by a well characterized system of cortical patches, which provided the test bed for our comparison. We showed that neural population information about face viewpoint was readily accessible with fMRI MVPA from all face patches, in agreement with single-unit data. Information about face identity, although it was very strongly represented in the populations of units of the anterior face patches, could not be retrieved from the same data. The discrepancy was especially striking in patch AL, where neurons encode both the identity and viewpoint of human faces. From an analysis of the characteristics of the neural representations for viewpoint and identity, we conclude that fMRI MVPA cannot decode information contained in the weakly clustered neuronal responses responsible for coding the identity of human faces in the macaque brain. Although further studies are needed to elucidate the relationship between information decodable from fMRI multivoxel patterns versus single-unit populations for other variables in other brain regions, our result has important implications for the interpretation of negative findings in fMRI multivoxel pattern analyses.

Additional Information

© 2015 the authors. For the first six months after publication SfN's license will be exclusive. Beginning six months after publication the Work will be made freely available to the public on SfN's website to copy, distribute, or display under a Creative Commons Attribution 4.0 International (CC BY 4.0) license (https://creativecommons.org/licenses/by/4.0/). T Received Sept. 29, 2014; revised Jan. 5, 2015; accepted Jan. 7, 2015. This work was supported by the National Institutes of Health (Grant 1R01EY019702 to D.Y.T.). We thank Nicole Schweers for outstanding technical assistance with fMRI data collection; Le Chang for collecting additional single unit data; and Johan Carlin, Rufin VanRullen, Tim Kietzmann, Ethan Meyers, Kalanit Grill-Spector, and anonymous reviewers for helpful comments on various versions of the manuscript. Author contributions: J.D., A.O.d.B., and D.Y.T. designed research; J.D. and A.O.d.B. performed research; J.D. analyzed data; J.D., A.O.d.B., and D.Y.T. wrote the paper. The authors declare no competing financial interests.

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