The brain controls everything we do. Every thought, movement, decision, conversation and action depends on different parts of the brain working together — and working reliably.
When dementia causes changes within the brain, the abilities that the brain supports begin to change too. But those changes don’t always happen in the way people expect.
Why Abilities Come and Go
One of the most confusing aspects of dementia is that abilities don’t disappear in a straight line.
A person may complete a familiar task independently one day and need support the next. They may follow a conversation for twenty minutes and then suddenly lose track. They may know a family member’s name on Monday and struggle to find it on Tuesday.
To those around them, this can look inconsistent — even deliberate. But these fluctuations are usually a direct result of what is physically happening inside the brain.
To understand why, it helps to think about two things: where information is stored, and how it gets from one place to another.
Storage: Where Information Lives
Different areas of the brain are responsible for holding different kinds of information and ability — memories, language, familiar skills, recognition, and much more.
In dementia, these storage areas can become damaged. Over time, some become destroyed.
When that happens, the information held there becomes harder to reach — and eventually, it may no longer be there at all. This is why some abilities decline gradually and why, in the later stages of dementia, certain things that were once possible are no longer available.
Transport: How Information Travels
Storage is only part of the picture. The brain also relies on a complex network of connections and chemical messengers to carry information between different areas.
Think of it like a postal system. A letter might be sitting ready to send, but if the delivery network isn’t working properly, it may arrive late, arrive incomplete, or not arrive at all.
In dementia, these chemical messengers — the brain’s delivery system — can become less effective. Connections between brain cells become damaged. The network that carries information becomes unreliable.
This is why a person can sometimes access an ability and sometimes can’t — even when the information itself hasn’t been lost. The storage may still be there. The difficulty is in the delivery.
Sometimes They Can, Sometimes They Can’t
This distinction matters, because it changes how we make sense of what we see.
When a person struggles with something today that they managed yesterday, it doesn’t always mean that ability has gone. It may mean that the brain couldn’t reliably access it in that moment. The connection wasn’t made. The message didn’t get through.
Thinking about abilities as available or unavailable — rather than present or absent — is a more accurate and more useful way of understanding what’s happening.
An unavailable ability isn’t necessarily a lost one. The person may still have the skill, knowledge or experience. Reaching it has simply become more difficult, and less predictable.
What This Means in Practice
Understanding the difference between storage and transport helps explain something important: the same person can appear quite capable at one moment and genuinely struggle the next — and neither reflects effort, motivation, or choice.
It also means that assuming someone can’t do something, just because they struggled earlier, may not be accurate. The ability might simply have been unavailable at that moment.
Rather than focusing solely on what has been lost, we can stay curious about what remains — and recognise that access to skills and information is affected as well as the skills and information themselves.
This awareness doesn’t change the condition. But it does change how we understand the person living with it, and how we choose to offer support.
A Final Thought
Dementia is a condition of brain change — and that change affects both where information is held and how reliably it can be reached.
When we understand that, the fluctuations make more sense. The person isn’t being inconsistent. Their brain is doing its best with a system that is gradually becoming less reliable.
That’s a very different thing — and it’s worth holding onto.