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We know depression is linked to variations in the way our brains are wired, but new research suggests that people who go through a depressive episode actually see the world around them differently.
And the team behind the study hopes that a better understanding of how visual information is processed in the brains of people with depression could help inform our treatment approaches in the future.
The researchers wanted to analyze how the cerebral cortex – responsible for receiving messages from the five senses – handled an optical illusion, testing it with 111 people who were experiencing major depressive episodes and 29 people who were not.
The optical test used in the study – patches A and B and patches C and D are the same. (Salmela et al, J. Psychiatry Neurosci., 2021)
The trick, which you can see above, places identical brightness and contrast patches on different backgrounds, and the variation in context is usually enough to trick the brain into believing that the middle sections themselves are different.
“What was surprising is that depressed patients perceived the contrast of the images shown differently from non-depressed individuals,” explains psychologist Viljami Salmela of the University of Helsinki in Finland.
The brains of people with depression were more likely to be absorbed into the contrasting part of the illusion, while there was little difference between groups in the brightness part of the trick.
It is possible that a weaker contrast signal is transmitted from the retina to the cortex in people with depression, although more research is needed to determine exactly what is happening – it is possible that changes are occurring in them. information returned from the eyes, or how it is processed in the brain, or both.
What makes optical illusion such a good test is that it challenges the eyes and the brain to make sense of what is seen and to balance brightness and contrast. It could also be telling that contrast testing involves rotation, unlike brightness.
“Because contrast suppression is orientation specific and relies on cortical processing, our results suggest that people with a major depressive episode have normal retinal processing but altered cortical contrast normalization,” the researchers write. in their article.
“In addition, contrast suppression was also reduced in patients with unipolar CT [major depressive disorder], bipolar disorder and borderline personality disorder. “
This is not the first time that researchers have discovered a curious link between depression and visual processing in the brain, although it does give experts better insight into the neural mechanisms of people with major depressive disorder.
There are a few limitations to the study: the team used participants’ self-report rather than brain scans to assess what they were seeing. It is also possible that medications for depression influence some of the changes in visual processing.
However, similar results have been seen in people with schizophrenia and bipolar disorder, suggesting that this type of change in the way the eyes and brain perceive the outside world may be common to several psychological disorders.
“It would be beneficial to assess and further develop the usability of perception tests, both as research methods and as potential means of identifying information processing disturbances in patients,” says Salmela.
The research was published in the Journal of Psychiatry and Neuroscience.
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