Activation in a Frontoparietal Cortical Network Underlies Individual Differences in the Performance of an Embedded Figures Task

Elizabeth Walter,Paul Dassonville,Antonio Verdejo García

doi:10.1371/journal.pone.0020742

Abstract

The Embedded Figures Test (EFT) requires observers to search for a simple geometric shape hidden inside a more complex figure. Surprisingly, performance in the EFT is negatively correlated with susceptibility to illusions of spatial orientation, such as the Roelofs effect. Using fMRI, we previously demonstrated that regions in parietal cortex are involved in the contextual processing associated with the Roelofs task. In the present study, we found that similar parietal regions (superior parietal cortex and precuneus) were more active during the EFT than during a simple matching task. Importantly, these parietal activations overlapped with regions found to be involved during contextual processing in the Roelofs illusion. Additional parietal and frontal areas, in the right hemisphere, showed strong correlations between brain activity and behavioral performance during the search task. We propose that the posterior parietal regions are necessary for processing contextual information across many different, but related visuospatial tasks, with additional parietal and frontal regions serving to coordinate this processing in participants proficient in the task.

Highlights

In an increasingly chaotic visual environment, we are often challenged to find a particular object hidden among distracting items
Witkin and colleagues [3] noted an inverse correlation between Embedded Figures Test (EFT) performance and susceptibility to an illusion of context – the rod-and-frame illusion, in which a vertical rod is seen as slightly tilted when viewed in the presence of a surrounding frame tilted at an angle away from vertical [4]
Work in our lab (Dassonville, Walter, and Bochsler, 2007, presented at the Annual Meeting of the Vision Sciences Society) has recently demonstrated that performance in the EFT is negatively correlated with susceptibility to another contextual visual illusion, the induced Roelofs effect

Summary

Introduction

In an increasingly chaotic visual environment, we are often challenged to find a particular object hidden among distracting items. Work in our lab (Dassonville, Walter, and Bochsler, 2007, presented at the Annual Meeting of the Vision Sciences Society) has recently demonstrated that performance in the EFT is negatively correlated with susceptibility to another contextual visual illusion, the induced Roelofs effect (in which the perceived location of a target is biased to the left or right when presented in the context of a large illuminated frame that is offset right or left of the observer’s midsagittal plane, respectively; [6,7,8]) These tasks appear to be linked by virtue of the need to suppress contextual information in order to perform optimally (i.e., to score well on the EFT and to be immune to the Roelofs and rod-and-frame illusions)

Objectives

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Results

Conclusion