Objective:

To study qEEG microstates and their cortical sources during changing Visio-Spatial Working Memory (VSWM) load in patients with schizophrenia as compared to healthy subjects.

Background:

Spatio-temporal dynamics of the quasi-stable EEG “functional microstates” and their intracranial generators can potentially be a state and trait marker for different cognitive and diseased states. Working memory deficits, a stable aspect of schizophrenia, tested by computer administered VSWM task with simultaneous dense array EEG acquisition to assess large scale brain networks can broaden our understanding of the disease and contribute in improving diagnostic accuracy.

Design/Methods:

After taking informed consent, 30 patients diagnosed with schizophrenia (as per DSM-5 criteria) and 30 age-matched controls were administered questionnaires (Edinburgh Handedness Inventory, Hindi MMSE, SAPS, and SANS). Thereafter, 128 channel EEG, ECG, and GSR (Galvanic Skin Resistance) were recorded during eyes closed, eyes open, and VSWM task performance. Following which, EEG preprocessing, down sampling, average referencing and Independent Component Analysis were done. Epoch wise data from each experimental condition was extracted and subjected to microstate analysis. Further, cortical generators of each microstate map were found. Statistical analysis was done to compare temporal microstate parameters (Global explained variance, number of time frames, mean duration, time coverage, and segment count density) and cortical sources of each microstate map in and across the groups.

Results:

A novel topographical map whose Global Explained Variance, Time Coverage, and Segment Count Density was significantly reduced in patients with schizophrenia associated with hypoactivation at right superior and medial frontal gyrus during pre-encoding phase of VSWM task which could potentially be a trait marker for schizophrenia.

Conclusions:

Spatio-temporal parameters of EEG microstates could distinguish patients with schizophrenia from controls.