Having depression makes the effects of some optical illusions less pronounced, a new study suggests.
Finnish researchers tested the visual perception of people with and without depression, using small squares of the same color on different backgrounds.
The depressed patients experienced the visual illusion presented on a computer screen as significantly weaker.
Visual perception is likely related to the processing of information in the cerebral cortex – the outermost layer of the brain involved in sensation, perception, memory, and conscious thoughts.
The scientists say there is altered cortical processing of visual contrast during a depressive episode.
This change is likely to be present with multiple types of depression and will partially recover as patients get better, they add.
The middle squares of A and B are the same; the middle squares of C and D are the same. Compared to people without depression, patients with depression did not feel as much of a contrast in the middle squares – hence, they generally had weaker visual perception
“What came as a surprise was that depressed patients perceived the contrast of the displayed images differently than non-depressed persons,” says Academy Research Fellow Viljami Salmela at the University of Helsinki.
For the study, researchers recruited 111 patients with unipolar depression, bipolar disorder, and borderline personality disorder who had major depressive episodes.
An additional 29 people without depression were recruited to act as controls for comparison.
The brightness of the small squares A and B is exactly the same, but they are perceived differently due to the difference in the backgrounds. A dark background improves brightness; a bright background reduces the brightness
Participants completed two visual perception tests in which they compared the brightness and contrast of simple patterns, as shown below.
The first test, ‘contrast induction’, consists of two squares, labeled A and B, each of which contains smaller squares.
While the larger squares are a different color, the smaller squares on the inside are the same color.
So the brightness of A and B are exactly the same, but B is usually perceived by the human brain as darker due to a lighter surrounding background.
DEPRESSION AFFECTS ONE IN TEN ON ONE POINT
While it is normal to feel down from time to time, people with depression can feel persistent unhappiness for weeks or months.
Depression can affect anyone at any age and is quite common – about one in ten people is likely to experience it at some point in their lifetime.
Depression is a real health condition that people cannot just ignore or ‘get out’.
Symptoms and effects vary, but may include feeling constantly upset or hopeless, or losing interest in things you used to enjoy.
It can also cause physical symptoms such as sleep problems, fatigue, a low appetite or sex drive, and even physical pain.
In extreme cases, it can lead to thoughts of suicide.
Traumatic events can cause it, and people with a family history may be more at risk.
It is important to see a doctor if you think you or someone you know is suffering from depression as it can be managed with lifestyle changes, therapy or medication.
Source: NHS Choices
The perceptual difference between the middle squares A and B was similar for both groups, the researchers found.
For the second test, ‘contrast suppression’, participants were presented with two more squares, which also contained smaller squares, labeled C and D.
Again, the center squares of C and D are identical, consisting of vertical black and white lines.
But the larger squares are different – C has vertical lines like the center square, while D has horizontal squares.
The center square of D is generally perceived as bolder than the center square of C, due to C’s collinear background – meaning the lines are aligned.
The contrasts of the backgrounds are identical and only the orientation relative to the center grid is different
Perception of this illusion was markedly weaker in the depressed patients than in the controls, the researchers found.
“Because contrast suppression is orientation specific and depends on cortical processing, our results suggest that people experiencing a depressive episode have normal retinal processing but altered cortical contrast normalization,” they say in their paper.
In addition, contrast suppression was similarly reduced in patients with unipolar MDD [major depressive disorder], bipolar disorder and borderline personality disorder. ‘
Identifying the changes in brain function that underlie mental disorders is important to increase understanding of how mental disorders develop and how effective therapies can be developed, the experts believe.
They have called for further research into altered brain processing of visual information caused by depression.
“It would be helpful to assess and further develop the usefulness of perception tests, both as research methods and potential ways to identify information processing disruptions in patients,” Salmela said.
For example, perception testing can serve as an additional tool in assessing the effect of different therapies as treatment progresses.
However, “depression cannot be diagnosed by testing visual perception as the observed differences are small and manifest specifically when comparing groups,” Salmela said.
The study is published in the Journal of Psychiatry and Neuroscience
Optical illusion of squares appearing to be moving leaves the internet baffled
A bizarre optical illusion makes still images appear to move.
The static image, with a gray square made of smaller gray squares, appears to move with every mouse movement.
To some, it also seems to move slightly, as if it vibrates nervously even without scrolling.
In reality, however, the image still remains with the sense of movement, just a devil trick of the brain.
The static image, an aberrant illusion of motion, appears to move with every mouse movement, when in fact it is static
The image was shared on Reddit, where users disagreed on how the image appears to move.
The image was captioned, “This is not GIF,” some users got sick of, with one comment, “I don’t feel so good.”
Another user shared what they believed was the reason behind the confusing illusion.
They noted, ‘I had to zoom in all the way to figure it out – the center square has the same pattern as the outer area, but rotated 90 degrees.
“For some reason, the shadow pattern that is rotated makes the brain pop.”
Another came to the same conclusion: ‘It seems that the way the center piece is cut before turning it makes your brain try to put it back together.
“The cutting angle + 90 degrees of rotation = brain confusion.”
Meanwhile, another user suggested a color theory behind the illusion.
They wrote, ‘For everyone who cares, the color contrast between dark and light creates the optical illusion, also known as abnormal movement illusion
They added that they believed Japanese psychology expert “Akiyoshi Hitaoka was involved in its creation.”
A creative user asked, “Can this image have the same effect as a tattoo?”