Fourier power, subjective distance, and object categories all provide plausible models of BOLD responses in scene-selective visual areas.

Mark D Lescroart,Dustin E Stansbury,Jack L Gallant

doi:10.3389/fncom.2015.00135

Mark D Lescroart, Dustin E Stansbury + Show 1 more

Open Access

https://doi.org/10.3389/fncom.2015.00135

Copy DOI

Abstract

Perception of natural visual scenes activates several functional areas in the human brain, including the Parahippocampal Place Area (PPA), Retrosplenial Complex (RSC), and the Occipital Place Area (OPA). It is currently unclear what specific scene-related features are represented in these areas. Previous studies have suggested that PPA, RSC, and/or OPA might represent at least three qualitatively different classes of features: (1) 2D features related to Fourier power; (2) 3D spatial features such as the distance to objects in a scene; or (3) abstract features such as the categories of objects in a scene. To determine which of these hypotheses best describes the visual representation in scene-selective areas, we applied voxel-wise modeling (VM) to BOLD fMRI responses elicited by a set of 1386 images of natural scenes. VM provides an efficient method for testing competing hypotheses by comparing predictions of brain activity based on encoding models that instantiate each hypothesis. Here we evaluated three different encoding models that instantiate each of the three hypotheses listed above. We used linear regression to fit each encoding model to the fMRI data recorded from each voxel, and we evaluated each fit model by estimating the amount of variance it predicted in a withheld portion of the data set. We found that voxel-wise models based on Fourier power or the subjective distance to objects in each scene predicted much of the variance predicted by a model based on object categories. Furthermore, the response variance explained by these three models is largely shared, and the individual models explain little unique variance in responses. Based on an evaluation of previous studies and the data we present here, we conclude that there is currently no good basis to favor any one of the three alternative hypotheses about visual representation in scene-selective areas. We offer suggestions for further studies that may help resolve this issue.

Highlights

FMRI experiments have shown that natural scene perception activates several distinct functional areas in the human cerebral cortex
To investigate how natural scenes are represented in sceneselective areas in the human brain, we analyzed BOLD fMRI signals evoked by a large set of natural images (These data were collected for two studies from our laboratory that were published previously: Naselaris et al, 2012 and Stansbury et al, 2013)
Several areas in the human brain respond to visual scenes, but which specific scene-related features are represented in these areas remains unclear

Summary

Introduction

FMRI experiments have shown that natural scene perception activates several distinct functional areas in the human cerebral cortex. These include the Parahippocampal Place Area (PPA), Retrosplenial Complex (RSC), and the Occipital Place Area (OPA, known as the Temporal Occipital Sulcus or TOS) A third position is that scene-selective areas represent information about the semantic categories of natural scenes or their constituent objects (Walther et al, 2009, 2011; Huth et al, 2012; Stansbury et al, 2013)

Methods

Results

Conclusion