Fronto-parietal network function during cued visual search in the first-episode schizophrenia spectrum

Abstract

Cognitive impairments account for significant morbidity in schizophrenia and are present at disease onset. Controlled processes are particularly susceptible and may contribute to pervasive selective attention deficits. The present study assessed fronto-parietal attention network (FPAN) functioning during cue presentation on a visual search task in first-episode schizophrenia spectrum patients (FE) and its relation to symptom burden and community functioning. Brain activity was recorded with magnetoencephalography from 38 FE and 38 healthy controls (HC) during blocks of pop-out and serial search target detection. Activity during cue presentation was compared between groups across bilateral FPAN regions (frontal eye fields (FEF), inferior frontal gyrus (IFG), midcingulate cortex (MCC), and intraparietal sulcus (IPS)). FE exhibited greater right hemisphere IFG activity despite worse performance relative to HC. Performance and FPAN activity were not correlated in HC. Among FE, however, stronger activity within right hemisphere FEF and IFG was associated with faster responses. Stronger right IPS and left IFG activity in patients was also associated with reduced negative symptoms and improved community functioning, respectively. Increased reliance on the FPAN for task completion suggests an inefficient cognitive control network and might reflect a compensation for impaired attentional deployment during target detection, a strategy employed by those with less severe illness. These findings represent a critical step towards identifying the neural substrates of negative symptoms and impaired neurocognition at disease onset.

Keywords: Attention; First-episode; Fronto-parietal attention network; Magnetoencephalography; Schizophrenia.

Figure 1.

The visual search task used in the present study. In the pop-out version (A) the cue-target color remained consistent across trials and all distractors during the target array were of a uniform color. During the serial search task (B), cue-target color varied across trials and all target array distractors had unique colors. Cortical activity was examined during the Cue period.

Figure 2.

Cortical activity averaged over the 500ms cue period for HC (A) and FE (B) as well as quantification of activity within each region displayed by group. Regions of a fronto-parietal network selected for analysis based on previous literature utilizing feature-based cues. Error bars represent SEM. *p<.01.

Figure 3.

Partial regression plots depicting relationship between response time and RH FEF (A) and RH IFG (B) activity, GF: Role measure of community functioning and LH IFG activity (C), and the inexpressivity negative symptom dimension and RH IPS activity (D).