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Patients with depression may have altered cortical processing of visual contrast during a major depressive episode.
University of Helsinki researchers confirmed in a recent study, published in the Journal of Psychiatry and Neuroscience, that individuals with depression process visual information differently, likely due to the processing of information in the cerebral cortex.1
The study utilized 2 visual tests to compare the processing of visual information by participants with depression compared with the control group, while assessing retinal and cortical processing. Test 1 was a brightness induction test that assessed retinal processing, in which participants compared the perceived luminance of uniform patches that were presented on a computer screen. Test 2 was a contrast suppression test assessing cortical processing, in which participants compared the perceived contrast of gratings that were presented with collinearly or orthogonally oriented backgrounds.
Participants with depression perceived the visual illusion presented in the patterns as weaker and the contrast as moderately stronger than those in the control group.
“What came as a surprise was that depressed patients perceived the contrast of the images shown differently from nondepressed individuals,” said Academy of Finland Research Fellow Viljami Salmela, PhD. “The contrast was suppressed by roughly 20% among nondepressed subjects, while the corresponding figure for depressed patients was roughly 5%.”2
The study authors concluded that the reduced contrast suppression may be caused by decreased retinal feedforward or cortical feedback signals.
“Because we observed intact brightness induction, our results suggest normal retinal but altered cortical processing of visual contrast during a major depressive episode. This alteration is likely to be present in multiple types of depression and to partially normalize upon remission,” the authors stated.1
The researchers believe these finding warrant further study to better understand how the brain’s processing is altered by depression.
“It would be beneficial to assess and further develop the usability of perception tests, as both research methods and potential ways of identifying disturbances of information processing in patients,” Salmela said. “However, depression cannot be identified by testing visual perception, since the observed differences are small and manifested specifically when comparing groups.”2
1. Salmela V, Socada L, Söderholm J, et al. Reduced visual contrast suppression during major depressive episodes. J Psychiatry Neurosci. 2021;46(2):E222-E231.
2. University of Helsinki. Depression affects visual perception. News release. March 29, 2021. https://www.newswise.com/articles/depression-affects-visual-perception?sc=dwhr&xy=5013482