Many people adjust their actions after negative experiences by trying to learn what caused those outcomes. Anxious individuals tend draw strong conclusions after single negative events and might generalize those to situations where threats are unlikely or far away, leading them to avoid situations even when they are objectively safe. This can maintain or worsen anxiety over time.
Two systems
The brain uses two complementary systems to learn from these experiences: a slow one (linked to the striatum) that updates beliefs gradually, and a fast one (linked to the amygdala) that reacts quickly to change and is mostly involved when threats come close and fast responding is necessary. When the balance between these systems is disrupted, as we think happens in anxiety, this can lead to excessive avoidance. In the long term, Bob Bramson aims to restore healthy learning in anxiety:
“The first step in this research is to show that in healthy individuals these systems are balanced to sometimes learn fast and sometimes learn more gradually. We will first measure how healthy individuals learn from threats and rewards in different situations. Then, we will interfere with these systems one-by-one, using ultrasound stimulation, and expect that the non-stimulated system becomes dominant, leading to predictable changes in learning.”
State of art measuring and stimulation
To test this, Bramson will use transcranial ultrasound stimulation (TUS) to modulate activity in deep brain areas, while monitoring brain responses with high-precision magnetoencephalography (MEG). These techniques have never been combined before, providing unprecedented insights into how information learned from earlier outcomes can contribute to current decisions.
In this experiment, participants will choose to approach or avoid targets offering money or mild electric shocks. By varying the proximity of the targets and the reliability of the outcomes, Bramson can test how those brain systems are involved differently when threats are close or far away, and more or less predictable. In one experiment, he will test whether anxious individuals have specific biases in learning that can be attributed to one of these learning systems. In a second experiment he will test whether those biases can potentially be changed with brain stimulation.
Together, these studies will set the stage for future exploration of novel treatments according to Bramson: “Changing the way we learn by using brain stimulation is promising for future treatments of anxiety. If we can show how anxious individuals learn differently by relying too much on one system, and also show that we can alter the balance between these systems the we have a promising starting point to for exploring actual treatment enhancement based on brain stimulation.”
