Hyperactivation of left inferior parietal lobule and left temporal gyri shortens resting EEG microstate in schizophrenia.

Objective: The momentary spatial configuration of the brain electric field at the scalp reflects quasi-stable "functional microstates" caused by activity of different intracranial generators. There is paucity in literature on the intracranial generators of resting state EEG microstate alterations in stable patients with schizophrenia. The present study aimed to investigate resting state microstate alterations and their neural generators in patients with schizophrenia and their first-degree relatives as compared to healthy controls in an attempt to establish state and trait marker.

Method: Thirty-four patients with schizophrenia (DSM-5 criteria), 29 first-degree relatives and 25 matched healthy controls participated in the study. Brain activity during eyes closed condition was recorded using 128 channel electroencephalography. Microstates were clustered into 5 maps across groups according to their topography. Microstate map parameters and their cortical sources were compared among groups.

Results: Map 5 mean duration (χ(2) = 7.617, p = 0.022) was significantly lower in patients compared to controls (U = 256, p = 0.010). Maximum activation was seen in left inferior parietal lobule (MNI coordinates: -65, -35, 25, Log-F = 0.748). Suprathreshold cortical voxels with increased activations were found localized at left temporal gyri.

Conclusion: Hyperactivation in left inferior parietal lobule and temporal gyri might have shortened Map 5 duration at rest in patients with schizophrenia. This could imply microstate alterations as the potential state marker of schizophrenia.