Hyperdeactivation of the Default Mode Network in People With Schizophrenia When Focusing Attention in Space

Abstract

When studying selective attention in people with schizophrenia (PSZ), a counterintuitive but replicated finding has been that PSZ display larger performance benefits than healthy control subjects (HCS) by cues that predicts the location of a target stimulus relative to non-predictive cues. Possible explanations are that PSZ hyperfocus attention in response to predictive cues, or that an inability to maintain a broad attentional window impairs performance when the cue is non-predictive. Over-recruitment of regions involved in top-down focusing of spatial attention in response to predictive cues would support the former possibility, and an inappropriate recruitment of these regions in response to non-predictive cues the latter. We probed regions of the dorsal attention network while PSZ (N = 20) and HCS (N = 20) performed a visuospatial attention task. A central cue either predicted at which of 4 peripheral locations a target signal would appear, or it gave no information about the target location. As observed previously, PSZ displayed a larger reaction time difference between predictive and non-predictive cue trials than HCS. Activity in frontoparietal and occipital regions was greater for predictive than non-predictive cues. This effect was almost identical between PSZ and HCS. There was no sign of over-recruitment when the cue was predictive, or of inappropriate recruitment when the cue was non-predictive. However, PSZ differed from HCS in their cue-dependent deactivation of the default mode network. Unexpectedly, PSZ displayed significantly greater deactivation than HCS in predictive cue trials, which may reflect a tendency to expend more processing resources when focusing attention in space.

Keywords: default network; fMRI; top-down.

Fig. 1.

(A) Components of a Spatial Attentional Resource Allocation Task (SARAT) trial. Target onset was preceded by a central cue. Either 1 or all 4 locations could be cued. On one-third of trials, the cue was not followed by a target. (B) Average (±SEM) reaction time in people with schizophrenia (PSZ) and healthy control subjects (HCS). (C) Average (±SEM) omission errors, expressed as percentage of all trials. *P < .05, ***P < .001, in paired or independent-samples t test.

Fig. 2.

Brain regions displaying a significant blood oxygen-level dependent (BOLD) signal difference between predictive and non-predictive cue trials across all 40 participants. Group activation maps are overlaid onto the average of all 40 anatomical scans in Talairach space. The numbering corresponds to regions of interest (ROIs) in table 2. The graph displays average (±SEM) cue-induced activity over all ROIs for each cue type in healthy controls subjects (HCS) and people with schizophrenia (PSZ). ***P < .001 in paired t test.

Fig. 3.

Brain regions displaying cue-induced deactivation across all 40 participants. Purple circles demarcate 7-mm spheres centered on peak foci of the task-negative network identified by Fox et al. Only spheres with ≥50% overlap with regions deactivated by the present task were defined as regions of interest (ROIs). The numbering corresponds to ROIs in table 3. The graph displays average (±SEM) blood oxygen-level dependent (BOLD) activity over all ROIs in healthy controls subjects (HCS) and people with schizophrenia (PSZ) for predictive and non-predictive cue trials. *P < .05 in paired or independent-samples t test.