A new study examines how the fusiform gyrus helps us distinguish between reality and imagination. (Image credit: Jaroslav Kushta via Getty Images)
Imagination depends on the ability to separate reality from fiction – and now scientists have identified possible mechanisms in the brain that contribute to this distinction. They suggest that these mechanisms may play a significant role in conditions such as schizophrenia, which can distort the perception of reality.
A paper published June 5 in the journal Neuron explored these mechanisms. Scientists know from previous studies that a certain part of the brain — the fusiform gyrus, a large structure located between the two hemispheres of the brain — is active both when we perceive something in reality and when we imagine it, one of the study’s authors, Nadine Dijkstra, a neuroscientist at University College London, told Live Science.
“However, we found that activity levels in this area predict whether you think something is real or not, regardless of whether you see it or imagine it,” she added.
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The fusiform gyrus is involved in high-level visual processing, such as recognizing objects and faces based on their appearance. The study suggests that during imagination, the signal strength is lower compared to perception; this difference in signal strength allows the brain to differentiate between the two states. That is, if the activity exceeds a certain threshold, the brain interprets it as reality.
To reach their conclusions, the scientists used functional magnetic resonance imaging (fMRI), a technique that tracks blood flow as an indirect measure of brain activity. In a series of experiments, 26 participants were asked to look for diagonal lines on a screen with dynamic noise — such as television static — and report whether the lines were present. Half the time, the lines were indeed on the screen; the other half, they were not.
At the same time, participants were asked to imagine lines that either ran in the same direction as the real lines or ran perpendicularly, depending on the round. They also reported how vivid the images they perceived were.
“The idea was that sometimes participants imagined the same lines [they saw on the screen], and sometimes they imagined different lines,” Dijkstra said. “We noticed that when they imagined the same lines, they were more likely to say they were seeing real lines, even though there was nothing on the screen.”
In other words, by presenting an expected visual image, you can trick your brain into believing it is real.
The fMRI scans helped the researchers track patterns of activity in specific areas of the brain associated with perception and imagination. The fusiform gyrus was active both when the lines were imaginary and when they were real. However, when the activity exceeded a certain threshold, the study participants believed they were real, Dijkstra noted.
“In general, the activation during imagination [alone] is not intense enough to cross that threshold,” she added.
When activity in the fusiform gyrus increased, there was also an increase in activity in the anterior insula, an area
Sourse: www.livescience.com
