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Dementia patients struggle with change because of damage to general intelligence brain networks

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Published: 18 March 2022

People with dementia struggle to cope with changes in their environment because of damage to areas of the brain known as ‘multiple demand networks’, highly-evolved areas of the brain that support general intelligence, a NIHR-supported study has revealed.

There are many different types of dementia, such as Alzheimer’s disease and frontotemporal dementia (FTD), which are characterised by the build-up of different toxic proteins in different parts of the brain.

This means symptoms of dementia vary, and can include problems with memory, speech, behaviour or vision. But one symptom seen across every type of dementia is a difficulty in responding to unexpected situations.

Dr Thomas Cope from the MRC Cognition and Brain Science Unit and Department of Clinical Neurosciences at the University of Cambridge said: “At the heart of all dementias is one core symptom, which is that when things change or go unexpectedly, people find it very difficult.”

To understand why this happens, researchers supported by the NIHR Cambridge Biomedical Research Centre analysed data from 75 patients with one of four types of dementia that affect different areas of the brain.

The patients, together with 48 healthy volunteers, listened to changing sounds while their brain activity was recorded by a machine which measures tiny magnetic fields produced by electrical currents in the brain. Unlike traditional MRI scanners, these machines allow very precise timing of what is happening in the brain and when.

During the scan, volunteers watched David Attenborough’s Planet Earth, but without its soundtrack – while listening to a series of beeps. The beeps occurred at a steady pattern, but occasionally a beep would be different, for example a higher pitch or different volume.

The team found that the unusual beep triggered two responses in the brain: an immediate response followed by a second response, around a fifth of a second later.

The initial response came from the basic auditory system, recognising that it had heard a beep. This response was the same in the patients and healthy volunteers.

The second response, however, recognised that the beep was unusual. This response was much smaller among the people with dementia than among the healthy volunteers. Put simply, in the healthy volunteers, the brain was better at recognising something had changed.

Researchers looked at which brain areas activated during the task and how they were connected up, and combined their data with that from MRI scans, which show the structure of the brain. They showed that damage to areas of the brain known as ‘multiple demand networks’ was associated with a reduction in the later response.

Multiple demand networks, which are found both at the front and rear of the brain, are areas of the brain that do not have a specific task, but instead are involved in general intelligence – for example problems solving. They are highly evolved, found only in humans, primates and more intelligent animals. It is these networks that allow us to be flexible in our environment.

While the research does not point to any treatments that may alleviate the symptom, it reinforces advice given to dementia patients and their families.

Dr Cope adds: “The advice I give in my clinics is that you can help people who are affected by dementia by taking a lot more time to signpost changes, flagging to them that you’re going to start talking about something different or you’re going to do something different. And then repeat yourself more when there's a change, and understand why it’s important to be patient as the brain recognises the new situation.”

Although their study only looked at patients with dementia, the findings may explain similar phenomena experienced by people living with conditions such as schizophrenia, where brain networks can become disrupted.

Professor John O'Brien, NIHR National Specialty Lead for Dementias, said:

“The ability to cope with change is a difficult aspect of dementia which impacts both those with the condition but those in caring roles too. 

“The team at Cambridge have helped identify very important and intriguing results within dementia research. We are excited to see how the findings from the trial translate across not only dementia but wider mental health research in general.”

The results of their experiment have been published in the Journal of Neuroscience.

The NIHR runs the Join Dementia Research service in partnership with Alzheimer’s Research UK, Alzheimer Scotland and Alzheimer’s Society. Join Dementia Research enables anyone over 18 with or without a diagnosis to register to take part in a range of studies. Many researchers across the UK recruit very well to their studies through Join Dementia Research.

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