Tuesday July 29 2014
Fear may be unpleasant but it has its uses
"Pea-sized brain hub could shed light on depression," BBC News reports. UK scientists think they have identified part of the brain responsible for feelings of foreboding. This part of the brain, called the habenula, may also be associated with depression.
The headline is based on a small study that used brain scans to look at brain activity in volunteers subjected to a Pavlovian-style series of experiments.
These volunteers were shown a series of abstract images associated with a chance of receiving or losing £1, receiving no outcome, or receiving a painful electric shock. The researchers hoped the volunteers would soon learn which abstract image was associated with the painful electric shock and this would elicit feelings of fear, pessimism and dread – a so-called conditioning response.
The researchers found activity in the habenula region increased when the volunteers were exposed to the "painful" image, suggesting it plays a role in warning the body and the rest of the brain when something bad is likely to happen.
On one level, the habenula appears to fulfil an important function; a warning system may allow us to avoid a potential harm, or at least learn from our mistakes.
The researchers speculate an overactive habenula may be associated with depression and general anxiety disorder – making people feel constantly fearful and concerned about the future.
While interesting, this is still theoretical research. It is difficult to see what current practical implications it has.
Where did the story come from?
The study was carried out by researchers from University College London and the University of Cambridge in the UK, the Japanese National Institute for Information and Communications Technology, and the Université de Lausanne, Switzerland. It was funded by the Medical Research Council.
The study was published in the peer-reviewed journal PNAS and has been made available on an open access basis, so it is free to read online.
The news coverage concentrated on the potential of the habenula as a target for the treatment of depression.
The researchers concluded the data in the current study suggest the habenula contributes to the generation of a number of depressive symptoms, such as anhedonia (inability to experience pleasure from activities usually found enjoyable) and aberrant decision making.
However, the current study didn't actually investigate the role of the habenula in depression or similar disorders.
What kind of research was this?
This was an experimental study on people that aimed to determine whether activity in a region of the brain called the habenula changes as people associate images with painful electric shocks.
What did the research involve?
The researchers recruited 23 people to participate in this study. The participants were shown seven abstract images. After being shown each of the images, one of four outcomes occurred:
- they won £1
- they lost £1
- they received a painful electric shock
- no outcome
Each of the seven images was associated with either:
- a 75% chance of a £1 win, 25% chance of no outcome
- a 25% chance of a £1 win, 75% chance of no outcome
- a 75% chance of a £1 loss, 25% chance of no outcome
- a 25% chance of a £1 loss, 75% chance of no outcome
- a 75% chance of a shock, 25% chance of no outcome
- a 25% chance of shock, 75% chance of no outcome
- a 100% chance of no outcome
While the researchers showed the participants the abstract images, they looked at part of the brain called the habenula using a technique called high-resolution functional magnetic resonance imaging (fMRI). fMRI measures brain activity by looking at blood flow.
After this, participants were asked to choose between two abstract images. This confirmed whether participants had associated the images with an outcome.
What were the basic results?
As the participants were shown more and more images, activity in the habenula region of the brain increased when images associated with receiving an electric shock were shown.
Activity in the habenula was greatest when an image associated with a shock was shown, and activity was not significantly different to baseline when images associated with a £1 win or loss were shown.
The researchers also found activity in the habenula was significantly different when images associated with a high probability of receiving a shock were compared with images associated with a low probability of receiving a shock.
At the end of the experiment, when participants were asked to choose between abstract images, images associated with electric shocks were least preferred. This demonstrates participants associated these images with receiving a shock.
How did the researchers interpret the results?
The researchers concluded their results show that in people, "The habenula encodes the dynamically changing negative motivational value of stimuli that predict primary punishments."
This study has found activity in a region of the brain called the habenula changes as people associate images with negative outcomes, in this case electric shocks.
Further research will be conducted to see whether there are any differences in the activity in the habenula in people with depression. If so, this may lead to new avenues for research into new treatments, but this is a long way off.
If you do find your thoughts dominated by feelings of fear and dread about the future, you may require specialist advice. The free and confidential NHS Choices mood self-assessment tool can guide you on whether to seek advice about your mood.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.