Perception and hallucinations

Vision and perception

Hallucinations are sometimes experienced by people living with dementia.

Understanding sight and perception problems and giving appropriate help, support and reassurance can help ensure feelings of safety. This is especially important at a time when the way they perceive the world around them may be changing.

What causes these problems?

The complicated process of seeing involves many different stages.

Information comes through our eyes to the brain. Here, it is interpreted in relation to our expectations (of what will be seen), other senses, thoughts and memories. We then become aware of what has been seen, or what is ‘perceived’.

Visuoperceptual difficulties

Problems that involve both vision and perception can be referred to as ‘visuoperceptual difficulties’. 

As there are many different stages involved in the seeing process, various different types and combinations of mistakes can occur. Common mistakes include:

Misperceptions

When a person sees one thing as something else, this is known as misperceptions. For example, mistaking a coat hanging up for a person, or a blue-coloured floor as water

Misidentifications 

Damage to specific parts of the brain can lead to problems identifying specific objects and people. For example, mistaking a son for a husband or brother.

Understanding mistakes

It is easy to see how these mistakes may lead to the person with dementia saying or doing things that do not make sense to others.

However, what they are experiencing is not a problem with thinking. In other words, it is not based on incorrect reasoning or ‘delusional thinking’. Instead, it is the result of damage to the visual system.