A brain structure that tracks negative events backfires in depression, a new study finds.
The habenula — a structure the size of a pea — reacts strangely to negative events, researchers have found.
It could help explain a common symptom of depression: dwelling on negative memories.
Professor Jonathan Roiser, one of the study’s authors, said:
“A prominent theory has suggested that a hyperactive habenula drives symptoms in people with depression: we set out to test that hypothesis.
Surprisingly, we saw the exact opposite of what we predicted.
In people with depression, habenula activity actually decreased when they thought they would get a shock.
This shows that in depressed people the habenula reacts in a fundamentally different way.
Although we still don’t know how or why this happens, it’s clear that the theory needs a rethink.”
The results come from comparing brain scans (fMRI) of 25 people with depression with those of 25 people who never experienced depression.
Dr. Rebecca Lawson, the study’s first author, said:
“The habenula’s role in depression is clearly much more complex than previously thought.
From this experimental fMRI study we can draw conclusions about the effects of anticipated shocks on habenula activation in depressed individuals compared with healthy volunteers.
We can only speculate as to how this deactivation is linked to symptoms, but it could be that this ancient part of the brain actually plays a protective role against depression.
Animal experiments have shown that stimulating the habenula leads to avoidance, and it is possible that this occurs for mental as well as physical negative events.
So one possible explanation is that the habenula may help us to avoid dwelling on unpleasant thoughts or memories, and when this is disrupted you get the excessive negative focus that is common in depression.”
The study was published in the journal Molecular Psychiatry (Lawson et al., 2016).
Brain image from Shutterstock