Innovative Laser Technique Unveils How the Brain Creates Visual Illusions

Scientists have advanced our understanding of visual perception by employing laser technology to examine how the brain perceives illusions. This groundbreaking research, conducted by the University of California, Berkeley in collaboration with the Allen Institute, reveals the neural circuits responsible for detecting edges and contours in visual stimuli, which are fundamental to how we interpret illusions. Central to their discovery are IC–encoder neurons, a specialized group of brain cells that facilitate the process of recurrent pattern completion—where the brain fills in missing information to perceive a coherent image.

The team used cutting-edge two-photon holographic optogenetics technology to stimulate these neurons and observe their activity patterns. Remarkably, they found that stimulating IC–encoder neurons in the absence of any actual illusion could evoke brain activity similar to that observed when illusions are present, such as the Kanizsa triangle or square. This indicates that these neurons play a crucial role in the brain's ability to generate perception based on neural feedback from higher visual areas.

The research also demonstrated that the brain actively constructs visual reality through feedback loops between higher and lower visual areas. When higher regions interpret an image as a shape or object, they send signals back to the primary visual cortex to reinforce that perception—even if the actual visual stimuli are incomplete or ambiguous. This process highlights perception as an active, constructive phenomenon rather than a passive receipt of information.

The use of Neuropixels probes in the study enabled the researchers to record detailed brain activity across different regions of mice brains with millisecond precision. Their findings challenge traditional views of vision as a straightforward process and suggest that our perception involves complex computations influenced by prior knowledge and neural feedback mechanisms. These insights could have significant implications for understanding neurological disorders like schizophrenia, where perception and object recognition are disrupted.

The study emphasizes the importance of specific neural cell types and circuits in visual perception and opens new avenues for research into how the brain constructs reality. It also underscores the potential to manipulate or influence perception through targeted neural stimulation, with possible applications in treating perceptual disorders.