Does monocular viewing improve target detection in hemispatial neglect?

Area of Science:

• Neuroscience
• Cognitive Psychology
• Ophthalmology

Background:

• Large posterior-cortical lesions can cause unilateral spatial neglect (USN), mimicking human syndromes.
• Recovery from USN in animals involves superior colliculus modulation, known as the Sprague effect.
• The Sprague effect suggests monocular occlusion might alleviate hemineglect by reducing contralesional collicular activity.

Purpose of the Study:

• To investigate the efficacy of monocular viewing in ameliorating left hemineglect in right-hemisphere damaged patients.
• To explore whether the observed improvements align with the Sprague effect model.
• To identify potential underlying mechanisms beyond the Sprague effect in visual attention recovery.

Main Methods:

• Twenty-six patients with right-hemisphere damage and USN performed a cancellation task.
• Performance was assessed under binocular, left-monocular, and right-monocular viewing conditions.
• Improvements in left hemineglect were compared across different viewing conditions.

Main Results:

• Thirteen patients (50%) showed reduced left hemineglect with left-monocular viewing compared to binocular viewing.
• Two patients improved with right-monocular viewing, while eleven showed no significant change.
• The results suggest the Sprague effect is not the sole explanation for monocular viewing benefits.

Conclusions:

• Left-monocular viewing can ameliorate hemineglect in a subset of patients with right-hemisphere damage.
• The Sprague effect may contribute but does not fully account for the observed improvements.
• Interocular differences in target detection and other neural structures likely play a role in visual attention recovery.