What Hallucinations in Dementia Really Reveal About the Brain
Hallucinations in dementia can be puzzling and sometimes frightening, both for the person experiencing them and for their loved ones. But these experiences are more than just random glitches—they actually offer important clues about what’s happening inside the brain.
When someone with dementia sees or hears things that aren’t there, it’s often because parts of their brain responsible for processing sensory information are not working as they should. The brain is made up of many specialized areas, each handling different tasks like memory, vision, or judgment. In dementia, damage to these areas disrupts how messages travel between them.
One reason hallucinations happen is that the balance between what we expect to see (top-down processing) and what our eyes actually detect (bottom-up processing) gets thrown off. Normally, our brains combine both types of information to make sense of the world. But when certain regions are damaged—especially those involved in vision or memory—the brain might fill in gaps with images or sounds that aren’t real.
Another factor is something called “deafferentation.” This means that when parts of the visual system stop receiving normal signals from the eyes due to disease or aging, other areas become overactive as they try to compensate. This overactivity can create vivid hallucinations.
Different types of dementia affect different parts of the brain and lead to different kinds of hallucinations. For example, people with Lewy body dementia often have very detailed visual hallucinations because this type specifically affects regions involved in perception and alertness.
Understanding why hallucinations occur helps us see them not just as symptoms but as windows into how a person’s brain is changing. They remind us that even though someone may seem confused or disconnected from reality on the outside, complex processes are still at work inside their mind—processes shaped by both biology and experience.
By paying attention to these experiences instead of dismissing them outright, caregivers can better support those living with dementia and help make sense out of moments when reality seems uncertain.
