Neurophysiological Evidence of Visual Cortical Alterations in Mild Primary Glaucoma: A Resting-State EEG Microstate Study.

Functional neuroimaging studies have identified glaucoma as a neurodegenerative disorder marked by cortical activity alterations. This study explored resting-state EEG microstates and their intracranial sources to assess cortical dysfunction in early-stage glaucoma. High-density 128-channel EEG recordings were obtained from subjects with mild primary open-angle glaucoma (POAG; n = 37), mild primary angle-closure glaucoma (PACG; n = 34), and healthy controls (n = 32) under eyes-closed (EC) and eyes-open (EO) conditions. Microstate topographies were analyzed using CARTOOL, and their cortical sources were localized using sLORETA. Microstate parameters were comparable across groups; however, significant differences were observed in intracranial source activity. In PACG, Map 4 during eyes-closed (EC) condition showed increased activation in visual cortical regions, including the middle occipital gyrus, lingual gyrus, and cuneus, suggesting excitotoxic overactivation. Under eyes-open (EO) conditions, both PACG and POAG groups demonstrated reduced activation in the anterior cingulate and frontal regions across Maps 1, 2, and 3, indicating dysfunction in cognitive control and executive networks. These findings indicate early cortical hypoactivation in attention, memory, and executive networks in both PACG and POAG, with additional increased visual cortical activity during eyes-closed conditions in PACG. This may reflect early functional reorganization within visual processing networks. Overall, EEG microstate source analysis demonstrates subtype-specific cortical alterations in glaucoma, supporting early central involvement in the disease process.