When our senses receive insufficient information about an object, the brain "fills in" its image based on previous experience. American scientists have studied in detail how this process unfolds.

Recent research in neurobiology and medicine has enabled scientists to describe the mechanisms underlying various cognitive processes, such as planning for the future in dreams, simultaneously remembering several things, and mentally creating maps of the environment.

Experiment with Mice

Experts from the Allen Institute (USA) conducted an experiment with mice to find out how illusions are formed in the brain. The results of their work were published in the journal Nature Neuroscience.

During the study, the researchers analyzed the neural activity in the brains of male and female mice at least six weeks old. The animals were shown two types of stimuli: complete images (such as lines or geometric shapes) and illusory contours of these images.

Discovery of Specialized Neurons

During the experiment, scientists discovered specialized neurons in the primary visual cortex that responded to illusory contours but not to individual parts of a complete image. When researchers stimulated these neurons with a laser, the mice perceived the image of an illusory contour even without any visual stimulus.

The Mechanism of Illusion Formation

The scientists concluded that neurons encoding sensory output (that is, what the mouse sees in response to a stimulus or its absence) are responsible for receiving and locally transmitting information from higher cortical areas to lower ones. These circuits in the lower regions can amplify the activity of neurons corresponding to previously formed expectations. As a result, an illusion arises—the brain "completes" the perceived visual stimulus based on past experience.