Brain’s Built-In Signal Threshold Helps Differentiate Imagination from Reality

A basic but inscrutable brain system may distinguish between reality and imagination. New research has found that there may be a “dial” in the fusiform that may influence whether we interpret something sensory as real or imagined. The research, published in the journal Neuron, also gives new understanding of conditions like schizophrenia, where perception and thought are not properly distinguished, leading the researchers to conclude that this threshold system is crucial to normal cognition and sensory decision-making.

Brain Distinguishes Reality from Imagination Using Signal Threshold in Visual Processing Region

As per a report in Live Science, researchers from University College London used functional MRI to examine brain activity in 26 volunteers as they viewed or imagined diagonal lines on a noisy screen. Half the time, the lines were real; the rest of the time, participants were asked to imagine lines, either matching or differing from the visual cues. When imagined visuals aligned with expected inputs, participants were more likely to report having “seen” something, even when nothing was displayed, indicating the brain's susceptibility to being tricked by strong internal signals.

The scans showed that both real and imagined stimuli activated the fusiform gyrus, but only when activity exceeded a specific intensity did the brain classify the input as “real”. This finding suggests that a threshold in this brain region helps determine reality perception. Notably, the anterior insula—a region linked to decision-making—also activated in tandem, potentially acting as a “reader” of the fusiform's signal strength.

Lead author Nadine Dijkstra noted that while imagination does stimulate the same region, the signal is usually too weak to convince the brain of external input. This technology is basic enough that it could aid us in understanding more about hallucinations and other mental health issues that alter the way we see.

Experts say the study paves the way for further research with more complex visual and real-world multimodal integration. The group seeks to investigate how people perceive faces, animals, and things. They're also curious if applying brain stimulation can be a route to enhancing imagined perception. Thomas Pace, a neuroscientist who wasn't involved with the research, said that the findings were a big step towards figuring out how reality monitoring works and how it could not work in cases like schizophrenia.