Neurobiological Mechanisms of Metacognitive Therapy - An Experimental Paradigm

Abstract

Introduction: The neurobiological mechanisms underlying the clinical effects of psychotherapy are scarcely understood. In particular, the modifying effects of psychotherapy on neuronal activity are largely unknown. We here present data from an innovative experimental paradigm using the example of a patient with treatment resistant obsessive-compulsive disorder (trOCD) who underwent implantation of bilateral electrodes for deep brain stimulation (DBS). The aim of the paradigm was to examine the short term effect of metacognitive therapy (MCT) on neuronal local field potentials (LFP) before and after 5 MCT sessions.

Methods: DBS electrodes were implanted bilaterally with stereotactic guidance in the bed nucleus of the stria terminalis/ internal capsule (BNST/IC). The period between implantation of the electrodes and the pacemaker was used for the experimental paradigm. DBS electrodes were externalized via extension cables, yielding the opportunity to record LFP directly from the BNST/IC. The experimental paradigm was designed as follows: (a) baseline recording of LFP from the BNST/IC, (b) application of 5 MCT sessions over 3 days, (c) post-MCT recording from the BNST/IC. The Obsessive-Compulsive Disorder- scale (OCD-S) was used to evaluate OCD symptoms.

Results: OCD symptoms decreased after MCT. These reductions were accompanied by a decrease of the relative power of theta band activity, while alpha, beta, and gamma band activity was significantly increased after MCT. Further, analysis of BNST/IC LFP and frontal cortex EEG coherence showed that MCT decreased theta frequency band synchronization.

Discussion: Implantation of DBS electrodes for treating psychiatric disorders offers the opportunity to gather data from neuronal circuits, and to compare effects of therapeutic interventions. Here, we demonstrate direct effects of MCT on neuronal oscillatory behavior, which may give possible cues for the neurobiological changes associated with psychotherapy.

Keywords: BNST/IC; deep brain stimulation; local field potential; metacognitive therapy; treatment resistance.

FIGURE 1

Illustration shows the LFPs were recorded as bipolar configuration from DBS electrodes from contacts 0 and 1 before and after MCT for a total of 300 s (100 s epoch was preferentially used to fulfill the stationarity criteria) (A). Parallel EEG was recorded as unipolar configuration according to 10/20 system from cortical surface electrodes F3 and F4 (frontal cortical/motor planning area). F3 and F4 electrodes were linked together with left and right mastoid (M1 + M2) as reference (B).

FIGURE 2

Relative power of LFPs in the BNST from DBS electrodes: The bar plots represent the mean ± SEM percentage of relative power of theta (4–8 Hz) band (A), alpha (8–12 Hz) band (B), beta (12–30 Hz) band (C) and gamma (30–100 Hz) band (D) oscillatory activity of LFPs recorded in the BNST of left and right electrodes with bipolar reference from contacts 0 vs. 1. Statistical significant differences were determined by paired sample t-test and is shown by asterisks (^∗p < 0.05 and ^∗∗p < 0.01).

FIGURE 3

Coherence of frontal cortical EEG and BNST-LFPs of DBS electrodes: The bar plots show the mean ± SEM ratio-transformed coherence of the theta (A), alpha (B), beta (C), and gamma (D) frequency band coherence between BNST-LFPs (left and right electrodes, bipolar reference from contacts 0 vs. 1) and the frontal cortical area (EEG left and right frontal cortex). Statistical significance was determined using paired sample t-test and is shown by asterisk (^∗p < 0.05 and ^∗∗p < 0.01).