The Brain Tour

What It Does

The cerebrum is the big one, the deeply folded outer brain that gives it its walnut appearance, and by far the largest part.

Nearly everything you would call thinking happens here: attention, language, reasoning, memory and conscious awareness, along with sensation and deliberate movement.

Those folds are grey matter, where the nerve cells themselves sit. Running underneath is white matter, bundled fibres carrying signals between regions, rather like cabling between rooms.

How Dementia Affects It

Dementia with Lewy bodies takes hold here. Small round clumps of protein, called Lewy bodies, collect in the grey matter and damage the nerve cells around them.

Families often notice alertness that comes and goes markedly from one hour to the next, visual hallucinations, vivid disturbed sleep, and stiffness or slowness of movement.

The cerebrum is also where vascular dementia does its damage. When blood flow to the brain is restricted, often after a stroke, or a series of very small ones, cells starved of oxygen die. Vascular dementia tends to progress in noticeable steps rather than a smooth decline.

What It Does

The frontal lobe is the seat of judgement and self-restraint. It weighs one option against another, anticipates consequences, and holds back the things we think but should not say.

It plans, sequences and initiates actions. It carries a great deal of what people mean when they talk about someone's personality, and it helps regulate mood.

It also plays a part in laying down long-term memories.

How Dementia Affects It

Frontotemporal dementia begins here, and it often arrives earlier in life than Alzheimer's, commonly between 45 and 65.

Because the damage lands on personality and restraint rather than on memory, the first signs are usually behavioural: tactless or uncharacteristic remarks, a loss of empathy, impulsive spending, a flattening of motivation, or rigid new routines.

Memory can stay relatively intact early on. That is precisely why this type is so often mistaken for depression, stress or a midlife crisis long before anyone thinks of dementia.

What It Does

The parietal lobe puts things in the right order, letters into words, digits into a sum, steps into a sequence. It is what lets you follow a recipe or work out change at the till.

It also gives you your body sense: knowing where your hand is without having to look at it.

And it locates objects in three dimensions, so you can reach out and pick something up without thinking about it.

How Dementia Affects It

This region is affected by posterior cortical atrophy, an uncommon form of Alzheimer's disease. It is driven by the same protein damage, but it starts at the back of the brain rather than in the memory centres.

Because the region handles space and sequence, the early difficulties look like eyesight problems: misjudging distances, losing your place on a line of text, bumping into door frames, being unable to find one item on a cluttered surface.

People often visit an optometrist several times, and get new glasses more than once, before anyone thinks to look at the brain.

What It Does

The temporal lobe makes sense of what you see and hear. It recognises a face, a voice, a familiar street, a piece of music.

It handles language in both directions, finding the right word, and knowing what a word means.

Tucked inside it is the hippocampus, a small curved structure doing two jobs that matter enormously: forming new memories, and keeping track of where you are and how places connect.

How Dementia Affects It

The hippocampus is where Alzheimer's disease usually starts. Two proteins, amyloid and tau, accumulate and damage the nerve cells there before the disease spreads outward.

That explains the pattern families recognise immediately: recent events do not stick, while memories from decades ago stay vivid. The same question is asked several times in one conversation. A route driven for thirty years stops making sense.

Some forms of frontotemporal dementia also affect this lobe. There, the earliest losses are of language, names, words, and factual knowledge about the world.

What It Does

The occipital lobe is where sight is actually assembled. Your eyes gather light; this region turns it into shape, colour, depth and movement, into a scene you understand.

It stays busy while you sleep, and is involved in producing dreams.

How Dementia Affects It

Like the parietal lobe, this area is affected by posterior cortical atrophy, the rare form of Alzheimer's that begins at the back of the brain.

The eyes themselves are healthy. The difficulty is interpretation: recognising an object in plain view, telling where one surface ends and the next begins, reading, or making sense of a patterned carpet or a dark doorway.

This is worth knowing at home. A great deal of what looks like confusion, stubbornness or refusal is in fact a person who genuinely cannot make out what is in front of them.

What It Does

The cerebellum sits beneath and behind the rest of the brain, and keeps movement smooth.

It manages balance and posture and fine-tunes coordination, turning a rough intention into a controlled action.

It contributes to attention and language too, though it is best known for the physical work.

How Dementia Affects It

Most dementias are progressive, meaning the damage reaches more regions over time. The cerebellum is usually affected later rather than first, but the hallmark Alzheimer's proteins do eventually build up here.

When they do, the effects are physical: unsteadiness, a changed walk, more frequent falls, and difficulty with movements that used to be automatic.

This is often the point at which families find that safe, practical help with walking, washing and moving around the home becomes the daily priority.