Brain-Memory5

Dementia is not just about losing your memory

“Dementia Friends” is an initiative from the Alzheimer’s Society and Public Health England. In this series of blogpost, I take an independent look at each of the five core messages of “Dementia Friends” and I try to explain why they are extremely important for raising public awareness of the dementias.

 

 

Dementia is a general term for a number of progressive diseases affecting over 800,000 people living in the UK, it is estimated.

The heart pumps blood around the circulation.

The liver is involved in making things and breaking down things in metabolism.

The functions of the brain are wide ranging.

There are about 100 billion nerve cells called neurones in the brain. Some of the connections between them indeed do nothing. It has been a conundrum of modern neuroscience to work out why so much intense connectivity is devoted to the brain in humans, compared to other animals.

For example, there’s a part of the brain involved in vision, near the back of the head, known as the ‘occipital cortex’. Horace Barlow, now Professor Emeritus in physiology at the University of Cambridge, who indeed supervised Prof Colin Blakemore, Professor Emeritus in physiology at the University of Oxford, in fact asked the very question which exemplifies one of the major problems with understanding our brain.

That is, why does the brain devote so many neurones in the occipital cortex to vision, when the functions such as colour and movement tracking are indeed in the eye of a fly.

The answer Barlow felt, and subsequently agreed to by many eminent people around the world, is that the brain is somehow involved in solving “the binding problem”. For example, when we perceive a bumble bee in front of us, we can somehow combine the colour, movement and shape (for example) of a moving bumble bee, together with it buzzing.

The brain combines these separate attributes into one giant perception, known as ‘gestalt’.

What an individual with dementia notices differently to before, on account of his or her dementia, will depend on the part of the brain which is affected. Indeed, cognitive neurologists are able to identify which part of the brain is likely to be affected from this constellation of symptoms, in much the same way cardiologists can identify the precise defect in the heart from hearing a murmur with a stethoscope.

In a dementia known as ‘posterior cortical atrophy’, the part of the brain involved with higher order visual processing can be affected, leading to real problems in perception. For example, that’s why the well known author has trouble in recognising coins from their shape from touching them in his pocket. This phenomenon is known as ‘agnosia’, meaning literally ‘lack of knowing’.

If a part of the brain which is deeply involved in personality and behaviour, it would not be a big surprise if that function is affected in a dementia which selectively goes for that part of the brain at first. That’s indeed what I showed and published in an international journal in 1999, for behavioural variant frontotemporal dementia, one of the young onset dementias.

If the circuits involved in encoding a new memory or learning, or retrieving short term memories are affected, a person living with dementia might have problems with these functions. That’s indeed what happens in the most common type of dementia in the world, the dementia of the Alzheimer Type. This arises in a part of the brain near the ear.

If the part of the brain in a dementia which is implicated in ‘semantic knowledge’, e.g. knowledge for categories such as animals or plants, you might get a semantic dementia. This also arises from a part of the brain near the ear, but slightly lower and slightly more laterally.

So it would therefore be a major mistake to think a person you encounter, with memory problems, must definitely be living with dementia.

And on top of this memory problems can be caused by ageing. It would be wrong to pathologise normal ageing in this way.

Severe memory problems can be caused by depression, particularly in the elderly.

In summary, dementia is not just about losing your memory.

Share This: