Deep Brain Stimulation (DBS) Increases Self-Confidence

Patients with obsessive compulsive disorder (OCD) experience unwanted intrusive thoughts (‘obsessions’) expressive of their anxious mode of relating to the world. They feel strong urges to repeatedly perform ritual-like behaviours (‘compulsions’). Our group at the Amsterdam University Medical Center currently treats 80 treatment-refractory OCD patients with DBS, an innovative treatment method in which a ‘neurostimulator’ is surgically implanted, providing stimulation to areas deep in the brain. In our OCD patients, stimulation is applied to areas located in the ventral striatum, near the ventral anterior limb of the internal capsule (vALIC)/nucleus accumbens. In the first placebo-controlled clinical study published on striatal-DBS for OCD, our group demonstrated a 72% symptom reduction in responders [1]. In contrast to regular drug treatments, OCD patients responded to DBS immediately (sometimes within seconds to minutes) when adequate stimulation parameters were identified.

One of the most striking changes patients repeatedly describe, both in the clinic and in qualitative interviews we carried out [2], is an immediate and persisting increase in self-confidence. Simultaneously, patients report a reduction in anxiety-related obsessions, while improvement in compulsivity symptoms typically requires additional behavioural therapy. In this article, we propose that the primary effect of DBS may be to increase the patient’s self-confidence. Our hypothesis is based in part on clinical observation and qualitative interviews we conducted [2]. Furthermore, we have observed that when DBS stimulation parameters are set too high, the patient behaves more impulsively, a sign of excessive self-confidence [3]. Drawing on the active inference framework [4], we hypothesise that DBS-induced changes in precision expectations may provide a neurocognitive explanation of the rapid change in self-confidence that our patients report.

What is Self-Confidence?

People are self-confident when they trust their abilities and surroundings. Self-confidence allows them to be open to the various action possibilities that are relevant to them [2]. We will therefore understand self-confidence in terms of the person’s experience of their power to act in the world. Self-confidence can be given a neurocognitive description in terms of ‘active inference’, the process of action selection that minimises the ‘surprise’ expected as a consequence of acting [4]. Agents expect their future sensory states to match those they value or desire, and are surprised when such expectations are violated. In active inference terms, an agent can be said to act with self-confidence when they trust their actions will lead to the outcomes they expect, and thereby minimise surprise [5].

Self-confidence is reduced in OCD. The person’s power to act in the world is severely diminished by their illness. OCD patients anticipate dangers such as contamination, and threats such as causing harm to others, or performing actions they find morally repugnant [6]. The reduced self-confidence our patients report is the result of their actions being driven by their anticipation of threat and danger. We suggest that DBS increases self-confidence by allowing the patient to again be open to other possibilities for action and not only those that relate to their fear and anxiety.

The Active Inference Account of OCD

In work on active inference, neurotransmitters such as dopamine are hypothesized to weigh the precision of action policies, ensuring agents act on policies which they have high confidence will minimise future surprise [5]. The ventral striatum is well known for playing a role in dopaminergic function [8]. Thus there is good reason to think the ventral striatum, in communication with a wide range of other areas, plays a role in weighing the precision of action policies [5]. We previously found that vALIC-DBS reduces excessive functional connectivity between the ventral striatum and medial prefrontal cortex, which critically predicted decreases in OCD symptoms [9]. Finding the optimal level of DBS in the ventral striatum normalises communication between these brain areas. Recent work in healthy individuals suggests that the ventral striatum and ventromedial prefrontal cortex track choice-dependent and choice-independent subjective confidence, respectively [10]. This finding agrees with our hypothesis that the ventral striatum plays a key role in setting the precision on action policies.

Concluding Remarks and Future Directions

DBS may prove an effective treatment for OCD patients because it allows the patient to once again be open to the many possible actions the world offers, and thereby increases their self-confidence. The subsequent improvements in OCD symptoms may be contingent on their regaining the power to act in the world. To test our hypothesis, future studies are needed that examine the effect of vALIC-DBS on precision expectations using behavioural tasks. These should also examine the underlying neural changes, which likely include changes in communication between the ventral striatum and a wider network of connected regions, including the ventromedial prefrontal cortex.

More research is also needed to establish whether the effects on self-confidence can only be achieved through DBS of the vALIC. Stimulating the subthalamic nucleus (STN) has been shown to reduce compulsivity, but is less anxiolytic than vALIC-DBS [12]. How does stimulation of STN, compared with vALIC, impact the patients’ openness to action possibilities and self-confidence? Our prediction is that as long as anxiety-related anticipation is not reduced, the patient will remain at least partly closed off from the many possibilities they care about and their self-confidence will remain relatively low.

DBS changes the structure of a patient’s field of inviting affordances [2]. This is, we suggest, why the patient experiences more self-confidence. As long as precision is high for anxious anticipations, this will result in the person focusing only on the dominant affordance(s) relating to their anxious state of anticipation. When anxiety reduces, the person is once again open to dealing with the many other action possibilities the environment makes available. The result of this openness and readiness for the world is increased self-confidence.