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Face neurons encode nonsemantic features

Bardon, Alexandra and Xiao, Will and Ponce, Carlos R. and Livingstone, Margaret S. and Kreiman, Gabriel (2022) Face neurons encode nonsemantic features. Proceedings of the National Academy of Sciences of the United States of America, 119 (16). Art. No. e2118705119. ISSN 0027-8424. doi:10.1073/pnas.2118705119.

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The primate inferior temporal cortex contains neurons that respond more strongly to faces than to other objects. Termed “face neurons,” these neurons are thought to be selective for faces as a semantic category. However, face neurons also partly respond to clocks, fruits, and single eyes, raising the question of whether face neurons are better described as selective for visual features related to faces but dissociable from them. We used a recently described algorithm, XDream, to evolve stimuli that strongly activated face neurons. XDream leverages a generative neural network that is not limited to realistic objects. Human participants assessed images evolved for face neurons and for nonface neurons and natural images depicting faces, cars, fruits, etc. Evolved images were consistently judged to be distinct from real faces. Images evolved for face neurons were rated as slightly more similar to faces than images evolved for nonface neurons. There was a correlation among natural images between face neuron activity and subjective “faceness” ratings, but this relationship did not hold for face neuron–evolved images, which triggered high activity but were rated low in faceness. Our results suggest that so-called face neurons are better described as tuned to visual features rather than semantic categories.

Item Type:Article
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URLURL TypeDescription Information ItemData
Xiao, Will0000-0001-5555-3217
Ponce, Carlos R.0000-0002-9887-3234
Livingstone, Margaret S.0000-0002-1950-0123
Kreiman, Gabriel0000-0003-3505-8475
Additional Information:© 2022 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC-BY-NC-ND). Contributed by Margaret S. Livingstone; received October 13, 2021; accepted February 17, 2022; reviewed by Marlene Behrmann and Sabine Kastner. Published April 4, 2022. This work was supported by NIH Grants R01EY026025, R01EY16187, and P30EY12196 and NSF Grant CCF-1231216. C.R.P. was supported by a Packard Fellowship. Author contributions: A.B., W.X., C.R.P., M.S.L., and G.K. designed research; A.B.,W.X., C.R.P., and M.S.L. performed research; A.B.,W.X., and G.K. analyzed data; and A.B.,W.X., C.R.P., M.S.L., and G.K. wrote the paper. The authors declare no competing interest. Data Availability: Psychophysics and neural recording data have been deposited on the lab website and are publicly accessible (, including part of data that were collected in previous work (18). This article contains supporting information online at
Funding AgencyGrant Number
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:face neurons; semantic tuning; neural coding; visual cortex
Issue or Number:16
Record Number:CaltechAUTHORS:20220405-458435400
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114153
Deposited By: Tony Diaz
Deposited On:06 Apr 2022 16:09
Last Modified:06 Apr 2022 16:09

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