Electroencephalogram Gamma Band Power Correlates with Anhedonia in a Community Sample

Major depression (MD) is a condition characterised by persistent sadness and apathy, sometimes accompanied by changes in sleep, appetite, and energy levels. It is highly heterogeneous, and depressive subtypes exhibit differing symptom profiles and patterns of brain activity. Background/Objectives: Currently, there are no physiological diagnostic means to detect depression or depressive subtypes. An emerging biomarker may be the electroencephalogram (EEG) band, gamma, due to the role of this frequency in reward processing and cognition. The aim of this work was to complete an exploratory study to investigate the interaction between gamma band power, depression, and four depressive subtypes. Methods: A correlative study between resting-state gamma band power and individual scores on the Zung Self-rating Depression Scale (SDS) was completed using exact standardised low-resolution electromagnetic tomography (eLORETA) using EEG data from a community sample of 100 participants, including not depressed and depressed participants, and four depressive subtypes (anhedonia-, cognitive- and somatic-depression and depressed mood). Results: There was no significant positive correlation between gamma band power and overall depression score. However, there was a significant positive correlation between anhedonia and gamma band power, predominantly in the left anterior cingulate cortex, which may be consistent with dysfunctional reward processing, a characteristic of anhedonia. Additional areas of significance included the posterior cingulate cortex and left middle and superior frontal cortex. Conclusions: These results provide preliminary support for neurophysiological indicators of depressive subtypes and may help inform diagnosis and treatment guidance for depression and depressive subtypes in the future.