Increased Delta as a Compensatory Strategy During Working Memory in High-Performing Patients with Schizophrenia

Working memory (WM) impairment is a core cognitive deficit in schizophrenia and has been linked to dysfunction in the gamma, alpha, and theta bands. However, successful WM performance in high-performing patients is less well characterized. This study aims to investigate modulation of the EEG signal during successful WM performance in schizophrenia and to examine how that modulation differs from controls. Patients with schizophrenia (n=7) and controls (n=9) had scalp EEG recorded during a modified Sternberg WM task with two difficulty levels. The task was subdivided into four stages (pre-trial baseline, encoding, retention, and probe). Task-induced amplitudes were computed for the gamma, beta, alpha, theta, and delta frequency bands for three midline electrodes (Fz, Cz, Oz). Averaged amplitudes were then computed in 14, one-second steps across the task for each participant. Repeated measures ANOVAs were conducted for each frequency band. Diagnosis did not predict WM performance. Additionally, patients and controls showed similar patterns of modulation in all frequency bands except delta (F(2.34, 32.78) = 3.26, p = .004). In delta, patients showed greater power during the encoding stage of the task the occipital location. No other group differences were found. This study indicates that greater power in the delta frequency band at occipital locations may be a potential compensatory strategy in high-performing patients who perform at the level of controls. Delta may play a role in long-range communication and may be involved in recruitment of other areas