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Updated: Jul 8, 2026
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Functional Magnetic Resonance Imaging (fMRI) of the Visual Cortex with Wide-View Retinotopic Stimulation
Published on: December 8, 2023
Neurophysiological Evidence of Visual Cortical Alterations in Mild Primary Glaucoma: A Resting-State EEG Microstate
Rupesh Samanchi1, Simran Kaur1, Tanuj Dada2
1Stress and Cognitive Electroimaging Laboratory, Department of Physiology, All India Institute of Medical Sciences, New Delhi, India.
Brain Topography
|July 6, 2026
Summary
Glaucoma, a neurodegenerative disorder, shows early cortical dysfunction. This study found reduced frontal brain activity in both primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) patients, with PACG also showing increased visual cortex activity.
Area of Science:
- Neuroscience
- Ophthalmology
- Neurodegenerative Disorders
Background:
- Glaucoma is increasingly recognized as a neurodegenerative disorder affecting the brain, not just the eye.
- Cortical activity alterations are observed in glaucoma patients.
- Understanding early central nervous system involvement is crucial for glaucoma management.
Purpose of the Study:
- To investigate resting-state electroencephalography (EEG) microstates and their intracranial sources in early-stage glaucoma.
- To assess cortical dysfunction in primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) subtypes.
- To differentiate early neurodegenerative changes in glaucoma subtypes.
Main Methods:
- High-density 128-channel EEG recordings were performed on 37 POAG, 34 PACG, and 32 healthy controls.
- EEG data were analyzed under eyes-closed (EC) and eyes-open (EO) conditions.
- Microstate analysis (CARTOOL) and source localization (sLORETA) were employed to identify cortical activity.
Main Results:
- Microstate parameters were similar across groups, but intracranial source activity differed significantly.
- PACG patients showed increased visual cortical activation (Map 4, EC), suggesting excitotoxicity.
- Both PACG and POAG groups exhibited reduced frontal activation (Maps 1-3, EO), indicating cognitive control network dysfunction.
Conclusions:
- Early-stage glaucoma involves subtype-specific cortical alterations.
- Hypoactivation in attention and executive networks is present in both POAG and PACG.
- PACG may involve early functional reorganization in visual processing networks, alongside central nervous system involvement.
