fMRI activation during face processing: Differential effects of spatial frequency manipulation in healthy controls and people with schizophrenia

Abstract

People with schizophrenia demonstrate perceptual organization impairments, and the potential contributions of such impairments to face processing in schizophrenia are not known. In the current study we sought to examine the neural substrates of emotionally-neutral face processing in schizophrenia by examining neural activity under three stimulus conditions: normal faces, faces with low-spatial frequency information removed (“High condition”), and faces with high spatial frequency information removed (“Low condition”). Face perception in the High condition may be more reliant on local feature integration processes, whereas perception in the Low condition may require more reliance on global form processing. Past studies of perceptual organization in schizophrenia indicate that patients perform more poorly with degraded stimuli, but also, when global information is absent (which is detrimental to performance for controls), patients perform better than controls. fMRI data from 14 patients and 13 controls was acquired using a 3.0-Tesla whole body scanner and was processed using SPM2. Images were spatially normalized to the MNI template and smoothed. Using a block design, the BOLD response during a gender-discrimination task under each condition was compared to a resting baseline with center fixation. Whole brain subtractions between patients and controls were examined for each condition, controlling for type I error. Areas of significantly different activation between groups were identified across all three conditions. Of note, in both degraded conditions, patients demonstrated greater activity in the fusiform gyrus compared to controls, suggesting that impairments in basic integration abilities may be compensated for by relatively increased activity in the fusiform gyrus under these degraded stimulus conditions. Behavioral data indicated high levels of accuracy for both groups, with a trend toward an interaction involving higher patient performance in the high condition and poorer patient performance in the low condition. Implications of these findings will be discussed.