The adage “seeing is believing,” is cliché, but there may be more truth to it than people realize. A study from Michigan State University investigated how the brain makes decisions about conflicting visual information. They found that the visual cortex, the part of the brain responsible for processing what we see, is more powerful than previously believed. The results demonstrated that higher-order brain areas usually involved in decision making are not active when the brain tries to reconcile visual data, suggesting the visual cortex makes the decision itself. In a sense, seeing may really be believing.
For the study, participants looked at two adjacent dot patterns on a projection screen while the researchers monitored their brain activity using an MRI scanner. Although the participants did not know it, each eye saw a different dot pattern—an effect accomplished through prisms—which created an optical illusion. When the eyes see different things, the brain switches between each input in an attempt to make sense of the conflict. Past research has shown that, in these instances, the brain’s association cortex (responsible for decision making and other higher-order processes) directs the brain to switch between the two inputs. However, these studies focused on optical illusions that the participant was aware of, unlike the present study in which the participants did not know they were simultaneously viewing two patterns.
In contrast to previous research studies, the participants in the present study did not exhibit increased brain activity in the association cortex. This indicates that the visual cortex made the decision to switch between inputs on its own.
“That is one sense in which our study is counterintuitive and surprising. The part of the brain that is responsible for seeing, for the apparently ‘simple’ act of generating the picture in our minds eye, turns out to have the ability to do something akin to choosing, as it actively switches between different interpretations of the visual input without any help from traditional ‘higher level’ areas of the brain,” explained lead study investigator Jan Brascamp, MSU assistant professor of psychology.
This research is published in the journal Nature Neuroscience.
Previous news in sensory processing: