Abstract
Abstract
Background
Metacognition is the ability to be aware of own mental activities. Metacognitive deficits are reliably reported in schizophrenia and metacognitive ability has been strongly linked to functional capacity. However, the neural correlates of metacognitive ability in schizophrenia is uncertain, although some evidence implicates the hippocampus as a critical structure in this group. We explored neural correlates of perceptual metacognitive accuracy in first episode psychosis (FEP) and healthy controls, hypothesizing that lower hippocampal volume would correlate with poorer metacognition in FEP only.
Methods
31 patients with FEP (9 female, aged between 19 and 39, mean age 25.95) and eighteen age, gender and education matched healthy controls (6 female, aged between 18 and 38, mean age 24.43) took part in the study. Brain structural T1s were acquired using MRI and all participants completed a perceptual metacognitive accuracy task outside of the scanner. Gray matter volumes for cortical and subcortical regions were calculated using Freesurfer’s “recon-all” pipeline (http://surfer.nmr.mgh.harvard.edu). Regions of interest (ROI) included prefrontal and hippocampal structures, as implicated in previous studies on metacognition. Comparisons between FEP and control groups were performed using t-tests for continuous variables (ROI volumes, metacognitive accuracy). Correlational analyses than explored relationships between ROI and metacognitive accuracy, by group.
Results
In the FEP group, metacognitive accuracy was significantly impaired compared to controls. There was no difference between groups on any of the ROI volume measures. Metacognitive accuracy in the FEP group correlated with total hippocampal volumes both in left hemisphere (r=.429, p=.016), and right hemisphere r=.487, p=.005). These relationships were localized to specific hippocampal subfields (left hippocampal head; r=.376, p=.037, left hippocampal body; r=.462, p=.009; right hippocampal head; r=.475, p=.007, right hippocampal body; r=.516, p=.003). In contrast, there were no statistically significant relationships between metacognitive accuracy and hippocampal volume in the control group (left hippocampus: r=-0.046, p=0.855, right hippocampus: r=.056, p=.826).
Discussion
Results of this study provide evidence of a positive relationship between hippocampal volumes and metacognitive accuracy in FEP only. This points to possible differences in the neural substrates of metacognition in schizophrenia, with hippocampus contributing to the poorer metacognitive performance frequently observed in patients. Metacognitive ability has important consequences for functional capacity, and these results are consistent with the suggestion that hippocampal pathophysiology might be central to cognitive deficit in schizophrenia.