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Examining the brain under threat

27.09.2017

In a nutshell: We are more likely to be surprised when we feel anxious. This is reflected in increased brain activity and disrupted connections within the brain.

View Paper Abstract
Examining the brain under threat

Novel or uncertain situations can make us a little anxious and more alert to potential danger. This state of hypervigilance is helpful in the case of real threats, but when it becomes persistent – such as in post-traumatic stress disorder (PTSD) – it can be incapacitating.

Encountering unexpected stimuli, like a change in a repetitive sequence of sounds, elicits a response in the brain called ‘prediction error’. This prediction error is increased in people with PTSD, and even in psychiatrically healthy people when they are made to feel anxious.

In most cases, when there is a mismatch between what we predict will happen and what actually happens, the brain has a process for adjusting and improving its prediction through connections between the front and the sides of the brain. This process and connections are disrupted during anxious hypervigilance, as discovered in a recent study by Brain Function CoE Chief Investigator Marta Garrido and colleagues.

The team presented a group of participants with a series of sounds designed to elicit surprise. Occasionally the participants heard a voice recording that alerted them to an impending electrical shock to the wrist (the threatening condition) or notified them that no shock would occur (the safe condition).

Compared to the safe condition, the threatening condition generated larger prediction errors in the brain, and led to an imbalance in the process of adjusting and improving predictions. Both processes were restored when the participants were given alprazolam, an anti-anxiety medication.

As well as revealing more detail about how the brain behaves during anxious hypervigilance, these findings offer a possible target for developing more selective drugs to treat conditions like PTSD.

Next steps:
The team will investigate whether the brain’s process for adjusting predictions is disrupted in people with anxiety disorders and, if so, gauge the extent of those disruptions in the brain’s connections.


Reference:
Cornwell, B. R., Garrido, M. I., Overstreet, C., Pine, D. S., & Grillon, C. (2017). The unpredictive brain under threat: A neurocomputational account of anxious hypervigilance. Biological Psychiatry, 82, 447–454.


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