Do you feel that your brain tends to predict the worst possible scenario? And then do you find yourself engaging in avoidance behavior? Now scientists from the University College London have found the responsible party — the habenula. This tiny part of the brain (half the size of a pea) tracks predictions regarding negative events and then essentially demotivates us.
Previous studies in animals have shown that habenula activity leads to avoidance because it suppresses dopamine, a brain chemical that typically increases feelings of motivation. In animals, habenula cells were found to activate when bad things happened or were expected.
In the current study, published in the journal Proceedings of the National Academy of Sciences, 23 healthy participants underwent brain scans that revealed how the habenula becomes activated in response to pictures associated with painful electric shocks. The opposite occurred when participants looked at pictures that predicted winning money.
“The habenula tracks our experiences, responding more the worse something is expected to be,” says senior author Dr. Jonathan Roiser of the University College London (UCL) Institute of Cognitive Neuroscience.
“For example, the habenula responds much more strongly when an electric shock is almost certain than when it is unlikely. In this study we showed that the habenula doesn’t just express whether something leads to negative events or not; it signals quite how much bad outcomes are expected.”
During the study, healthy participants were placed inside a functional magnetic resonance imaging (fMRI) scanner. Then they looked at a random sequence of pictures, each followed by a set chance of a good or bad outcome.
Volunteers occasionally had to press a button to show they were paying attention. By tracking habenula activity, researchers knew whether the participants were expecting good or bad scenarios.
“Fascinatingly, people were slower to press the button when the picture was associated with getting shocked, even though their response had no bearing on the outcome.” says lead author Dr. Rebecca Lawson, also at the UCL Institute of Cognitive Neuroscience.
“Furthermore, the slower people responded, the more reliably their habenula tracked associations with shocks. This demonstrates a crucial link between the habenula and motivated behavior, which may be the result of dopamine suppression.”
The habenula has also been associated with depression, and this study shows how it could trigger symptoms such as low motivation, pessimism, and a focus on negative experiences. A hyperactive habenula could lead to a high percentage of negative predictions.
“Other work shows that ketamine, which has profound and immediate benefits in patients who failed to respond to standard antidepressant medication, specifically dampens down habenula activity,” says Dr Roiser. “Therefore, understanding the habenula could help us to develop better treatments for treatment-resistant depression.”
Source: University College London