Fixation Task: A Simple Eye Movement Task Reveals an Impairment in Schizophrenia

Area of Science:

• Neuroscience
• Ophthalmology
• Psychiatry

Background:

• Fixation stability (FS) is crucial for visuomotor processing and can be assessed via eye-tracking.
• FS evaluation with and without distractors may identify endophenotype markers for schizophrenia (SCZ).

Purpose of the Study:

• To investigate fixation stability (FS) in antipsychotic-naïve/free SCZ, their first-degree relatives (FDRs), and healthy controls (HC).
• To assess the impact of distractors on FS in these groups.
• To explore FS as a potential endophenotype marker for SCZ.

Main Methods:

• High-frequency monocular eye tracking was used during a fixation stability task.
• Participants included 69 SCZ, 49 FDRs, and 76 HC.
• Data analyzed using ANCOVA and RMANCOVA to assess group differences and distractor effects.

Main Results:

• SCZ exhibited significantly poorer FS (higher fixation frequency, saccade amplitude, scanpath length) than controls, even without distractors.
• Distractors further degraded FS performance in SCZ.
• FDRs showed impaired median fixation duration.
• A rightward bias in distractor effect was observed in SCZ and FDRs.

Conclusions:

• FS is impaired in SCZ and is exacerbated by distractors.
• Observed laterality effects suggest a potential link between visual functional asymmetry and SCZ vulnerability.
• FS warrants further investigation as an illness marker across different clinical stages of SCZ.