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Brain’s “Habenula” Linked To Depression, Pessimism, Negative Thinking

People who expect bad things to happen may not actually be able to control a pessimistic outlook. Recently, British researchers discovered an area of the brain called the “habenula” warns us that something bad will happen. Although this tiny (smaller than a pea) sized region is useful for helping us learn from bad past experiences, if it is overactive, it can promote depressive thinking and pessimistic attitudes.

What the habenula does in the brain

The habenula is involved in many functions including: pain processing, reproductive behaviors, nutrition, sleep-wake cycles, stress, and learning. Lateral habenula function tends to have links to reward processing. It helps encode negative feedback or negative rewards. It is thought that the habenula may interact with the basal ganglia, and other neurotransmitter systems. The lateral habenula in particular is able to signal information-prediction errors and reward-prediction errors.

  • Activity: It becomes overactive when we have worse expectations for a particular scenario. The activity is thought to decrease in those with more optimistic outlooks.
  • Signaling: It tends to signal how much we expect negative outcomes. There is greater signaling when we expect significantly worse scenarios.
  • Tracking experiences: It is able to track our experiences and help us learn from past negative events.
  • Volume: The volume of the habenula tends to be reduced in those with depression. Neuron count has been shown to be decreased on the right side. Deep brain stimulation of the lateral habenula has been used in cases of treatment-resistant depression.

Research at the University College of London 2014

In one study conducted by Dr. Jonathan Roiser, it was discovered that an ancient part of the brain called the “habenula” responds more when we have bad expectations for a certain event or scenario. There tends to be a correlation between the degree to which the habenula responds and expectations of bad scenarios. A team of researchers at UCL (University College London) Institute of Cognitive Neuroscience scanned brain activity of 23 healthy women.

These women were shown random sets of pictures, some of which suggested powerful electric shocks being delivered to their left hands. All of the fMRI (functional magnetic resonance imaging) scans indicated that the electric-shock pictures lead to activation of the habenula. Not only did the habenula become active, but the response was significantly greater than the pictures without any shocks.

The research findings were published in the journal Proceedings Of The National Academy Of Sciences. Other research demonstrates that the illicit drug ketamine may have an fast-acting antidepressant effect as a result of its ability to reduce habenula activity. Read about ketamine nasal spray for depression if you aren’t familiar with the latest research.

What do these new findings from UCL suggest?

These findings suggest that targeting the habenula may be a promising new way to reduce depression. Additionally researchers may want to monitor habenula activity when testing an antidepressant to determine whether a new treatment option is effective. The author of the study, Dr. Roiser specifically discussed that it could help develop better treatments for “treatment resistant depression.”

The findings also suggest that people with an overactive habenula are much more likely to have negative outlooks, pessimistic thinking, and/or depression. Whether the habenula becomes overactive is thought to be largely influenced by genetics. This may prove to be yet another small, but helpful finding in better understanding depression and the way the brain works.

It is also important to keep in mind that the sample size of his study was relatively small (23 participants) and all were female. Further research is warranted to replicate results with a larger sample size and both male and female participants.  It is also important to understand that other regions of the brain interact with the habenula, and could influence activity.

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