The `Parahippocampal Place Area' Responds Selectively to High Spatial Frequencies

Defining the exact mechanisms by which the brain processes visual objects and scenes remains an unresolved challenge. Valuable clues to this process have emerged from the demonstration that clusters of neurons (‘‘modules’’) in inferior temporal cortex apparently respond selectively to specific categories of visual stimuli, such as places/scenes. However, the higher-order ‘‘category-selective’’ response could also reflect specific lower-level spatial factors. Here we tested this idea in multiple functional MRI experiments, in humans and macaque monkeys, by systematically manipulating the spatial content of geometrical shapes and natural images. These tests revealed that visual spatial discontinuities (as reflected by an increased response to high spatial frequencies) selectively activate a well-known place-selective region of visual cortex (the ‘‘parahippocampal place area’’) in humans. In macaques, we demonstrate a homologous cortical area, and show that it also responds selectively to higher spatial frequencies. The parahippocampal place area may use such information for detecting object borders and scene details during spatial perception and navigation. Citation: Rajimehr R, Devaney KJ, Bilenko NY, Young JC, Tootell RBH (2011) The ‘‘Parahippocampal Place Area’’ Responds Preferentially to High Spatial Frequencies in Humans and Monkeys. PLoS Biol 9(4): e1000608. doi:10.1371/journal.pbio.1000608 Academic Editor: David Whitney, University of California Davis, United States of America Received July 15, 2010; Accepted February 25, 2011; Published April 5, 2011 Copyright: 2011 Rajimehr et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was supported by the US National Institutes of Health (NIH Grants R01 MH67529 and R01 EY017081 to RBHT), the Martinos Center for Biomedical Imaging, the NCRR, and the MIND Institute. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Abbreviations: c/deg, cycles/degree; FFA, fusiform face area; FFT, fast Fourier transform; fMRI, functional magnetic resonance imaging; IT, inferior temporal; mFFA, monkey homolog of fusiform face area; mPPA, monkey homolog of parahippocampal place area; PPA, parahippocampal place area; SF, spatial frequency * E-mail: reza@nmr.mgh.harvard.edu