Correlations between exploratory eye movement, hallucination, and cortical gray matter volume in people with schizophrenia

Abstract

Background: Widespread cortical gray matter alternations in people with schizophrenia are correlated with both psychotic symptoms and cognitive/behavioral abnormalities, including the impairments of exploratory eye movement (EEM). Particularly, the loss of gray matter density is specifically related to deficits of the responsive search score (RSS) of EEM in schizophrenia. It is unknown, however, whether the schizophrenia-related RSS deficits are associated with certain psychotic symptoms, such as hallucinations.

Methods: In 33 participants with schizophrenia, the measurement of EEM, assessment of the hallucination severity using Positive and Negative Syndrome Scale (PANSS) and a voxel-based morphometric analysis of cortical gray matter volume (GMV) were conducted to investigate the relationships between the RSS of EEM, symptom severity, and GMV. In 29 matched healthy controls, the measurement of EEM and a voxel-based morphometric analysis of cortical GMV were also conducted to investigate the relationship between the RSS of EEM and GMV.

Results: In participants with schizophrenia, the hallucination severity was significantly negatively correlated with both the RSS and the GMV of a large number of brain regions in the frontal, temporal, parietal, orbitofrontal, calcarine, cingulate, and insular cortices, and rolandic operculum, hippocampus, parahippocampal gyrus, and thalamus. Also in participants with schizophrenia, the RSS was significantly positively correlated with the GMV in the left supplementary motor area (SMA), left superior frontal cortex (SFG), bilateral precentral gyri, bilateral postcentral gyri, and bilateral middle frontal cortices. More importantly, the GMV of the SMA, SFG, and precentral gyrus in the left hemisphere was not only significantly negatively correlated with the hallucination severity but also significantly positively correlated with the RSS. No significant correlation could be revealed between the RSS and the GMV of any brain regions in healthy controls.

Conclusions: There was a significantly negative association between the hallucination severity and the RSS of EEM, suggesting that the RSS may be a potential biomarker for predicting the hallucination severity of schizophrenia. Also, the GMV of the left SMA, SFG, and precentral gyrus may be the common substrates underlying both hallucination induction and the RSS in people with schizophrenia.

Keywords: Exploratory eye movement; Gray matter volume; Hallucination; Positive and negative syndrome scale; Schizophrenia.

Fig. 1

The original target figure (a) and two figures (b, c) that slightly differ from the target. Each of the two figures (b, c) is divided into seven sections (d, e)

Fig. 2

The Scatter plot showing the significantly negative correlations between the hallucination severity and the responsive search score (RSS) in 33 participants with schizophrenia. Data overlaps with two, three, and four individuals are indicated by different symbols, respectively

Fig. 3

Brain areas with the gray matter volume (GMV) negatively associated with the hallucination severity in 33 participants with schizophrenia (p < 0.05, corrected, cluster size > 16,799 mm³). The colored bars show t values. L = left; R = right

Fig. 4

Brain areas with the gray matter volume (GMV) positively associated with the responsive search score (RSS) in 33 participants with schizophrenia (p < 0.05, corrected, cluster size > 15,141 mm³). The colored bars show t values. L = left; R = right

Fig. 5

Overlapped areas (red color) between brain areas (deep yellow color) with GMV associated with the hallucination severity, and brain areas (green color) with the gray matter volume (GMV) associated with the responsive search score (RSS) in 33 participants with schizophrenia. L = left; R = right