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Edited by Larry R. Squire, Veterans Affairs San Diego Healthcare System, San Diego, CA, and approved November 4, 2016 (received for review May 21, 2016)
Significance
Neurons in the human parahippocampal cortex explicitly code for scenes, rather than people, animals, or objects. More specifically, they respond to outdoor pictures, rather than to indoor pictures, and to stimuli with rather than without spatial layout. These scene-selective neurons are spatially clustered and receive spatially clustered inputs reflected by an event-related local field potential (LFP). Furthermore, these neurons form a distributed population code that is less sparse than codes found elsewhere in the human medial temporal lobe. Our findings thus provide insight into the electrophysiological (single unit and LFP) substrates underlying the parahippocampal place area, a structure well-known from neuroimaging.
Abstract
Imaging, electrophysiological, and lesion studies have shown a relationship between the parahippocampal cortex (PHC) and the processing of spatial scenes. Our present knowledge of PHC, however, is restricted to the macroscopic properties and dynamics of bulk tissue; the behavior and selectivity of single parahippocampal neurons remains largely unknown. In this study, we analyzed responses from 630 parahippocampal neurons in 24 neurosurgical patients during visual stimulus presentation. We found a spatially clustered subpopulation of scene-selective units with an associated event-related field potential. These units form a population code that is more distributed for scenes than for other stimulus categories, and less sparse than elsewhere in the medial temporal lobe. Our electrophysiological findings provide insight into how individual units give rise to the population response observed with functional imaging in the parahippocampal place area.
Footnotes
↵1F.M. and S. Kornblith contributed equally to this work.
- ↵2To whom correspondence should be addressed. Email: florian.mormann{at}ukb.uni-bonn.de.
Author contributions: F.M., S. Kornblith, C.K., and I.F. designed research; F.M., M.C., M.J.I., A.K., R.Q.Q., and I.F. performed research; F.M., M.T., and S. Knieling assessed electrode localizations; I.F. performed all neurosurgical procedures; F.M. and S. Kornblith analyzed data; and F.M., S. Kornblith, C.K., and I.F. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1608159113/-/DCSupplemental.
Freely available online through the PNAS open access option.
Scene-selective coding by parahippocampal neurons
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