Summary: Researchers have identified spatial and temporal abnormalities in spontaneous fixational saccades as a potential biomarker for cognitive and positive symptoms in schizophrenia. By combining one-minute recordings of fixational eye movements from patients with a simple machine learning model, they were able to distinguish people with first-episode schizophrenia from healthy controls with 85% accuracy. These results indicate that fixational saccades—easy-to-record, objective eye movement measures—could become a complementary tool for diagnosis and for tracking cognitive and positive symptoms in schizophrenia.
Source: Chinese Academy of Science
In a study published online in Schizophrenia Bulletin, teams led by Dr. Wang Wei at the Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, and Dr. Wang Jijun at Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, report clear spatial and temporal abnormalities of spontaneous fixational saccades in patients with schizophrenia. These abnormalities correlate with measures of cognitive impairment and positive symptoms, suggesting that fixational saccades are a promising, accessible biomarker for schizophrenia-related dysfunction.
Schizophrenia is a severe, heterogeneous psychiatric disorder marked by positive symptoms (such as hallucinations, delusions, disorganized speech, and unusual behavior), negative symptoms (loss of normal functioning), and widespread cognitive deficits. These clinical features are linked to disruptions in neurotransmitter systems and to structural and functional changes across cortical, subcortical, and cerebellar circuits.
Visual fixation is a core human behavior that supports perception and decision-making. During fixation, the eyes make small, spontaneous movements—microsaccades and larger macrosaccades—collectively called fixational saccades. Because these eye movements depend on integrity of cortical-subcortical-cerebellar circuits and relate closely to cognitive processes, they provide a noninvasive window into brain function. Yet their characteristics in schizophrenia have been underexplored.
This study recorded fixational saccades from 140 drug-naïve patients experiencing a first episode of schizophrenia and from 160 age-matched healthy controls. Each participant completed ten separate trials of steady fixation, each lasting six seconds, yielding one minute of fixation data per person. Researchers then analyzed the spatial orientations and temporal patterns of the saccades and related those measures to clinical and cognitive assessments.
Key findings include a clear shift toward more vertically oriented saccades in patients, and an increased vertical displacement of saccades that were nominally horizontal. Temporally, fixational saccades—especially the horizontal ones—had longer durations, faster peak velocities, and larger amplitudes in the schizophrenia group compared with controls.
Crucially, these altered eye movement properties correlated with clinical measures. Longer durations of horizontal saccades were associated with worse cognitive performance, measured by the MCCB neurocognitive composite score, with particularly strong links to attention/vigilance and processing speed domains. The increased vertical deviation of horizontal saccades correlated with more severe positive symptoms, assessed by PANSS total and PANSS positive scores.
To evaluate diagnostic potential, researchers trained a straightforward K-nearest neighbors classifier using the one-minute fixation recordings. The model achieved 85% accuracy distinguishing patients from controls based solely on fixational saccade features, demonstrating the feasibility of an objective, eye-movement–based complementary diagnostic tool for schizophrenia.
Overall, the study supports fixational saccades as an accessible biomarker that captures both spatial and temporal abnormalities in eye movement behavior linked to cognitive deficits and positive symptoms in schizophrenia. Because recordings require only short, noninvasive fixation tasks, this approach could be scaled for clinical screening, longitudinal monitoring, or as an outcome measure in treatment studies targeting cognition and psychotic symptoms.
About this schizophrenia research news
Author: Press Office
Source: Chinese Academy of Science
Contact: Press Office – Chinese Academy of Science
Image: The image is credited to Neuroscience News
Original Research: Closed access. “Spatial and Temporal Abnormalities of Spontaneous Fixational Saccades and Their Correlates With Positive and Cognitive Symptoms in Schizophrenia” by Xu Liu et al., Schizophrenia Bulletin.
Abstract
Spatial and Temporal Abnormalities of Spontaneous Fixational Saccades and Their Correlates With Positive and Cognitive Symptoms in Schizophrenia
Background and Hypothesis
Visual fixation involves spontaneous microsaccades and macrosaccades that are sensitive to structural and functional integrity of cortical, subcortical, and cerebellar circuits. Given the role of these circuits in cognitive and behavioral dysfunction in schizophrenia, the authors hypothesized that patients would show abnormal fixational saccades and that these abnormalities would relate to clinical symptoms.
Study Design
Saccades were recorded from 140 drug-naïve, first-episode schizophrenia patients and 160 age-matched healthy controls during ten trials of six-second steady fixations. Symptom severity was rated with the Positive and Negative Syndrome Scale (PANSS). Cognitive performance was measured using the MCCB (Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus Cognitive Battery).
Study Results
Patients showed a higher proportion of vertically oriented fixational saccades and a greater vertical shift in saccades that were nominally horizontal. Horizontal saccades in patients had longer durations, higher peak velocities, and larger amplitudes. The vertical shift of horizontal saccades correlated with higher PANSS total and positive symptom scores, while longer horizontal saccade durations correlated with lower MCCB composite scores and poorer attention/vigilance and processing speed. Using these eye-movement features, a K-nearest neighbors model classified patients with 85% accuracy.
Conclusions:
These results identify spatial and temporal abnormalities of fixational saccades in schizophrenia and support the potential of fixational saccade measures as objective, easily obtained biomarkers for cognitive deficits, positive symptoms, and as complementary diagnostic indicators in schizophrenia.