Every second, the brain is flooded with sights, sounds, smells, and signals from inside the body. Yet only a fraction of this information reaches our conscious awareness, thanks to neural systems that filter out what is familiar or unimportant.This filtering happens constantly in everyday life. After a while, we may stop noticing the hum of an air conditioner, the feel of clothing against our skin, or a familiar smell in the room. The signals are still there, but the brain pushes them into the background so we can focus on new or potentially important information.A new study published in Neuroscience Bulletin suggests that mescaline, a chemical found in certain cacti that can cause hallucinations, may alter how the brain responds to incoming sensory information.Mescaline has been used in spiritual and ceremonial practices for thousands of years. It produces its effects partly by activating some of the same receptors that normally respond to serotonin, a chemical messenger that helps brain cells communicate and plays a role in mood, sleep, and sensory perception.By engaging these receptors, mescaline can change how people perceive colors, shapes, time, their surroundings, and even themselves.The cerebellum has traditionally been associated with coordinating movement and balance. But growing evidence suggests it is also involved in attention, emotion, memory, and the processing of sensory information.