People often ask a very reasonable question: how do scientists actually know which part of the brain does what? In dementia care, we hear phrases like “the hippocampus is involved in memory” or “the frontal lobes help us plan and organise”. But how did anyone figure that out in the first place? And how do researchers know they’ve got it right?
This post takes you through the fascinating journey of how understanding of the brain has developed – from early medical observations to modern brain scans – and what it all means for dementia, daily life, and the people we support.
The Brain, in Simple Terms
The brain is the body’s control centre. It is made up of different regions, each with its own roles, but all working together like a team. Scientists call these regions “lobes” (large areas with broad responsibilities) and “structures” (smaller parts with specific functions).
When we say, for example, that the “hippocampus supports memory”, we are talking about a particular structure found deep inside the brain that helps us store and retrieve information. But this kind of knowledge did not appear overnight — it has been built carefully over centuries through a combination of observation, testing, imaging, and repeated, verifiable evidence.
To understand how we know what we know, we need to start with the earliest clues.
What Doctors Learned from Injuries and Strokes
Long before brain scans existed, doctors made connections by observing what happened when a particular part of the brain was damaged. This is often referred to as the lesion model — “lesion” simply means an area of damage.
The Famous Case of Phineas Gage
Perhaps the best-known historical example is a railway worker called Phineas Gage who survived an accident in 1848 when a metal rod passed through the front of his brain. He lived – remarkably – but his personality changed dramatically. He became impulsive, impatient, and struggled with decision-making.
This case gave researchers their first major clue that the frontal lobes are important for behaviour, planning, and self-control. Although Gage’s story has been exaggerated over time, the core learning still stands.
What We Learned from Strokes
In the 19th and early 20th centuries, neurologists began comparing the symptoms of people who had strokes — where a specific blood vessel failure affects a specific brain area — with what those areas looked like after death. Over thousands of cases, patterns emerged:
- Damage to the left temporal lobe often caused language and speech difficulties.
- Damage to the occipital lobe often affected sight.
- Damage to the hippocampus affected memory and learning.
This was slow, careful, painstaking work — but it laid the foundations for everything we understand today.
How Modern Science Maps the Brain
The next leap came with the invention of brain scanning technology. These tools allowed researchers to see inside the living brain, watch it in action, and track changes over time.
CT and MRI: Seeing the Structure
CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) give clear, detailed pictures of the brain’s structure. MRI can show shrinkage (atrophy) in conditions like Alzheimer’s disease or vascular dementia.
For example, NHS guidance notes that shrinkage of the hippocampus is often visible in the early stages of Alzheimer’s disease. Seeing this in thousands of people with the same symptoms strengthens the evidence about the hippocampus’ role in memory.
fMRI: Watching the Brain Work
fMRI (functional MRI) measures blood flow in the brain. When we use a particular skill — such as talking, remembering, or recognising faces — blood flow increases in the relevant area. This lets scientists observe which regions activate during different tasks.
For example:
- Trying to remember a past event increases activity in the hippocampus.
- Solving a problem lights up the frontal lobes.
- Looking at a face activates a region called the fusiform face area.
These findings have been repeated across hundreds of studies, with thousands of participants of all ages, backgrounds, and abilities — one of the strongest indicators that they are accurate.
PET and SPECT Scans: Tracking Chemical Changes
PET (Positron Emission Tomography) and SPECT (Single Photon Emission Computed Tomography) scans show how energy and chemicals move through the brain.
These scans helped researchers understand:
- Which areas lose access to fuel (glucose) early in dementia.
- Where blood flow reduces in vascular dementia.
- How Lewy body dementia (LBD) affects attention and movement regions.
PET scans also show the distribution of proteins like amyloid and tau in Alzheimer’s disease. This supports current diagnostic pathways used by the NHS and TEWV NHS Trust.
How Do Scientists Know They’ve Got It Right?
Understanding the brain is not based on one study or one technique — it is based on many different kinds of evidence reinforcing each other.
1. Repeating Findings Across Thousands of People
If brain scans, case studies, and clinical assessments all show the same pattern again and again, researchers can be confident in the conclusion.
2. Using Multiple Tools to Double-Check
For example, if a person with Alzheimer’s disease shows:
- Memory difficulties in daily life,
- Changes in cognitive testing,
- Hippocampal shrinkage on MRI,
- Reduced glucose use in the same region on PET,
…then each piece of evidence supports the others.
3. Side-by-Side Comparison
Researchers compare people with and without a condition. If a consistent difference appears — such as reduced blood flow in the parietal lobes in Alzheimer’s disease — it strengthens the link.
4. Improvement or Decline Tells Us More
If a skill improves with rehabilitation or declines with damage, it helps confirm which brain regions are involved. For example:
- If stroke rehabilitation strengthens movement, it shows the movement area is recovering.
- If frontal lobe damage causes difficulties with planning, structure, or self-control, those abilities are linked to that region.
5. Collaboration Across Countries
Findings are compared across universities, hospitals, and labs worldwide. When different countries replicate the same results, confidence increases further.
What This Means for Dementia
Dementia is not one condition — it describes a group of symptoms caused by different diseases. Each type affects particular brain regions in its own pattern.
Alzheimer’s Disease
One of the earliest and most consistent findings is shrinkage in the hippocampus. This helps explain why remembering new events becomes difficult early on.
Vascular Dementia
In vascular dementia, reduced blood flow affects pathways between brain regions. This can lead to slower thinking, difficulties with planning, and changes in attention.
Lewy Body Dementia (LBD)
In LBD, chemical changes affect the areas responsible for attention, movement, and visual processing. This helps explain fluctuations, movement difficulties, and visual hallucinations.
Frontotemporal Dementia (FTD)
In FTD, the frontal and temporal lobes are affected. This can lead to changes in behaviour, language, and emotional regulation.
These patterns are verified through MRI, PET, clinical observation, and assessment, giving clinicians and carers a clearer picture of what is happening and why.
How This Knowledge Helps Us Support People
Understanding which parts of the brain are affected helps carers take a more compassionate, person-centred approach. Here are some practical examples.
If memory is affected (hippocampus):
- Use visual cues, labels, and repetition.
- Encourage routines that offer predictability.
If the frontal lobes are affected:
- Expect difficulties with planning or decision-making.
- Offer structured choices rather than open-ended questions (this or this, this or something else).
If the temporal lobes are affected (language):
- Use clear, simple sentences.
- Slow down the pace of conversation.
If the occipital lobe is affected (vision):
- Ensure good lighting and high contrast.
- Avoid cluttered environments.
The Brain Is Not a Set of Boxes
Although we talk about brain regions as if they work independently, they actually operate together as a network. This is why two people with the same diagnosis can look very different.
For example:
- Two people with Alzheimer’s disease may experience memory changes at different speeds.
- In vascular dementia, symptoms may vary depending on where blood flow is reduced.
- In LBD, fluctuations mean symptoms come and go.
This does not mean our understanding is wrong — it means the brain is wonderfully complex and adaptable, and each person’s experience is unique.
Reflection
Many carers share that once they understand why the person they support behaves or responds in a certain way, they feel calmer and more confident. Knowledge brings reassurance. Understanding the brain helps us recognise that behaviour is not deliberate, personal, or chosen — it is a natural response to neurological change.
And importantly, it reminds us that there is always a person behind the symptoms, doing their best with the abilities they still have.
Summary
- Scientists first learned about the brain through injuries, strokes, and careful observation.
- Modern tools like MRI, fMRI, PET and SPECT allow us to see the brain’s structure and activity in real time.
- We know findings are accurate because they are repeatable, consistent, and verified across many studies.
- Different types of dementia affect different brain regions in distinct ways.
- Understanding these regions helps carers provide supportive, compassionate, and tailored care.
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