Effects of subcallosal cingulate deep brain stimulation on negative self-bias in patients with treatment-resistant depression

Abstract

Background: The cognitive neuropsychological model states that antidepressant treatment alters emotional biases early in treatment, and after this initial change in emotional processing, environmental and social interactions allow for long-term/sustained changes in mood and behavior.

Objective: Changes in negative self-bias after chronic subcallosal cingulate (SCC) deep brain stimulation (DBS) were investigated with the hypothesis that treatment would lead to changes in emotional biases followed by changes in symptom severity.

Methods: Patients (N = 7) with treatment-resistant depression were assessed at three time points: pre-treatment; after one month stimulation; and after six months stimulation. The P1, P2, P3, and LPP (late positive potential) components of the event-related potential elicited by positive and negative trait adjectives were recorded in both a self-referential task and a general emotion recognition task.

Results: Results indicate that DBS reduced automatic attentional bias toward negative words early in treatment, as indexed by the P1 component, and controlled processing of negative words later in treatment, as indexed by the P3 component. Reduction in negative words endorsed as self-descriptive after six months DBS was associated with reduced depression severity after six months DBS. Change in emotional processing may be restricted to the self-referential task.

Conclusions: Together, these results suggest that the cognitive neuropsychological model, developed to explain the time-course of monoamine antidepressant treatment, may also be used as a framework to interpret the antidepressant effects of SCC DBS.

Keywords: Brodmann area 25; Electrical stimulation; Electroencephalography; Event-related potentials; Mood disorders; Subgenual cingulate.

Figure 1

Behavioral results from the self-referential task as a function of word valence (positive vs. negative) and time point (baseline vs. one month DBS vs. six months DBS). (A) The proportion of words endorsed as self-descriptive. (B) Reaction time to endorse words as self-descriptive. * denotes statistically significant changes relative to baseline at α = .05.

Figure 2

Event-related potentials elicited by positive and negative words at the three time points (baseline – black lines, one month DBS – red lines, and six months DBS – blue lines) in the self-referential task and general emotion recognition task at electrode Pz. * denotes statistically significant changes in ERP component amplitude relative to baseline at α = .05.

Figure 3

Relationship between percent change in proportion of negative words endorsed as self-descriptive and percent change in depression severity. (A) After one month DBS, the relationship between change in negative self-bias and depression severity was not statistically significant. (B) After six months DBS, there was a strong positive correlation between reduction in negative self-bias and reduced depression severity.