Imagination relies on our capacity to differentiate between what is real and what is not. Recent scientific findings are uncovering the brain mechanisms behind this crucial distinction, which is particularly relevant in conditions like schizophrenia and can significantly shape individuals’ perceptions of reality.
An article published in the journal on June 5th Neurons explored these mechanisms. Researchers have pinpointed specific brain regions from earlier studies, such as the spindle gyrus, a prominent ridge traversing two lobes of the brain, which activates when one experiences reality versus when one imagines something, noted lead researcher Nadine Dijkstra, a neuroscientist at University College London.
“What we discovered is that the activity level in this region could predict whether a perception was real or imagined,” she explained.
The fusiform gyrus plays a critical role in advanced visual processing, including the identification of objects and facial recognition. According to the study, the signal strength diminishes during imaginative experiences compared to actual perceptions. This disparity enables the brain to differentiate between the two; when neural activity surpasses a certain threshold, it is interpreted as reality.
To arrive at this conclusion, researchers employed functional magnetic resonance imaging (fMRI), a method that observes blood flow as an indirect indicator of brain activity. In a series of trials, 26 participants were tasked with identifying diagonal lines on a screen amidst dynamic noise, such as TV static, confirming the lines’ presence. In half of the instances, the lines were actually on display; in the other half, they were not.
Simultaneously, participants were instructed to visualize a line that either matched the displayed line or ran vertically, depending on the trial. They also reported the clarity of the images they perceived.
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“The key was that participants occasionally visualized the same line that they saw on-screen, and sometimes they envisioned different lines,” Dijkstra explained.
Essentially, when you imagine the anticipated visual, you can trick your brain into perceiving it as present.
fMRI scans assisted researchers in tracking activity patterns in particular brain regions tied to perception and imagination. The fusiform gyrus was active whether the lines were seen or merely imagined. However, once activity surpassed a certain threshold, participants concluded that it was real, Dijkstra stated.
“Generally, the activation from imagination alone is insufficient to exceed this threshold,” she added.
As the fusiform gyrus’s activity increased, there was a corresponding rise in activity in the Maejima brain region. The prefrontal cortex is significantly involved in cognitive functions like decision-making and problem-solving and appears to interpret real signals from the fusiform gyrus, but the precise mechanism of interaction between these two brain areas remains unclear.
One limitation acknowledged in this study is that researchers utilized simple stimuli.
“We are in the process of developing a paradigm to incorporate more complex stimuli, such as objects, faces, or animals,” she said. “Another avenue to explore is whether individuals may mix up imagined visuals with perceived ones by stimulating the brain at opportune moments.”
Thomas Pace, a neuroscientist at Australia’s Sunshine Coast University who did not participate in the study, remarked that Dijkstra’s team’s findings provide an essential understanding of how reality is distinguished from mental imagery.
“Our perception of reality hinges on a judgment based on signal strength, and by design, this system can be swayed by the power of our minds,” he conveyed via email. This represents “a finding that could elucidate how reality monitoring might falter and paves the way for understanding complex experiences, such as hallucinations.”
Future inquiries, he emphasized, should examine more intricate stimuli, like faces, to ascertain how this threshold-based system operates across various visual processing types. Real-world experiences are often multi-sensory and align with anticipations of how events intricately unfold. Such nuances were absent in the study’s focused visual tasks.
“Most crucial is the investigation of this system within clinical populations where reality monitoring, such as in schizophrenia, is disrupted, as it may provide valuable insights into both the robustness of these mechanisms and their clinical implications,” he added.
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Source: www.livescience.com