Amygdala Lateralization at Rest and during Viewing of Neutral Faces in Major Depressive Disorder Using Low-Resolution Brain Electromagnetic Tomography

Abstract

Neuroimaging experiments of amygdala activity during rest have shown abnormal amygdalar lateralization in Major Depressive Disorder (MDD). The current study is an exploratory investigation of the use of the neuroimaging technique Low Resolution Electromagnetic Tomography (LORETA) to measure current source density (CSD) in the amygdala. We examined seven adults with MDD and nine healthy control subjects at rest, and while they viewed images of emotionally neutral faces. The primary purpose was to compare the findings of LORETA with published findings using other neuroimaging techniques. Four frequency bands were examined: delta (1–3 Hz), theta (3–7 Hz), alpha (7–11 Hz), and beta (11–29 Hz).

Results showed that for both MDD and control groups, the right amygdala displayed higher overall activity (across frequencies) than the left, both at rest, and while viewing neutral faces. Results also showed that controls displayed significant differences between resting and viewing neutral images across all four bands in the right amygdala, with all four bands having higher CSD values in the right amygdala. There were no significant differences in CSD values between rest vs. viewing neutral images in the MDD group. Findings suggest a more pronounced lateralization effect in normal healthy controls than in MDD subjects when changing from a resting (eyes-closed) condition to viewing faces without emotional valence.