People with dementia struggle to cope with change because of damage to areas of the brain that support general intelligence, new research suggests.
Because of the different types of dementia, including Alzheimer’s disease, symptoms vary and can include problems with memory, speech, behaviour and vision.
However, experts say one symptom seen across every type of dementia is a difficulty in responding to unexpected situations.
The new study found that damage to areas of the brain known as multiple demand networks – highly-evolved regions of the organ that support general intelligence and allow people to be flexible in their environment- are behind the difficulty in coping with change.
Experts previously thought these networks do their own thing and just take in information, but the new findings indicate they are essential to how people perceive the world.
While the research does not point to any treatments that may alleviate the symptom, the research reinforces advice given to dementia patients and their families.
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.
“If people are in their own environment and everything is going to plan, then they are OK.
“But as soon as the kettle’s broken or they go somewhere new, they can find it very hard to deal with.”
He added: “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.”
Researchers analysed data from 75 patients, all of whom are affected by one of four types of dementia that affect different areas of the brain.
Brain activity of the patients, together with 48 healthy people, was recorded while they listened to changing sounds.
During the scan, the volunteers watched a silent film – 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 one would be different, for example at a higher pitch or a different volume.
Researchers found that the unusual beep triggered two responses in the brain – an immediate one followed by a second response around 200 milliseconds – a fifth of a second – later.
While the initial response was the same in the patients and healthy volunteers, coming from the basic auditory system, the second response recognised the beep was unusual.
According to the study, this response was much smaller in those with dementia than among the healthy volunteers.
In other words, people without dementia were better at recognising that something had changed.
When the researchers looked at which areas of the brain were activated during the task, they saw damage to the multiple demand networks was associated with a reduction in the later response.
The networks, which are found both at the front and back of the brain, are areas that do not have a specific task but instead are involved in general intelligence, for example problem solving.
They are highly evolved, found only in humans, primates and more intelligent animals.
Dr Cope said: “There’s a lot of controversy about what exactly multiple demand networks do and how involved they are in our basic perception of the world.
“There’s been an assumption that these intelligence networks work ‘above’ everything else, doing their own thing and just taking in information.
“But what we’ve shown is no, they’re fundamental to how we perceive the world.
“That’s why we can look at a picture and immediately pick out the faces and immediately pick out the relevant information, whereas somebody with dementia will look at that scene a bit more randomly and won’t immediately pick out what’s important.”
Although the study, published in the Journal of Neuroscience, 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.
The research was funded by the Medical Research Council and National Institute for Health Research, with additional support from Wellcome, the Biotechnology and Biological Sciences Research Council and the James S McDonnell Foundation.
