Dementia patients’ struggle to adapt to changes explained by University of Cambridge scientists
Damage to highly-evolved areas of the brain that support general intelligence is responsible for the difficulty dementia patients have with adapting to changes in their environment, say University of Cambridge researchers.
The struggle to adapt to unexpected situations is a symptom common to the many different types of dementia, which include Alzheimer’s disease to frontotemporal dementia (FTD).
Characterised by the build-up of toxic proteins in the brain, dementia symptoms can variously include problems with memory, speech, behaviour or vision.
But 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.”
Dr Cope and colleagues analysed data from 75 patients affected by one of four types of dementia affecting different areas of the brain to explore why this happens.
They, and 48 healthy control volunteers, listened to changing sounds while being monitored on a magnetoencephalography machine – a device to measure tiny magnetic fields produced by electrical currents in the brain. The machines are able to record very precisely the timing of what is happening in the brain.
The volunteers watched David Attenborough’s Planet Earth documentary, but without its soundtrack, while listening to a series of beeps at a steady pattern. Occasionally, the beep would be altered by putting it at a higher pitch or different volume, for example.
The team, who reported their results on Tuesday (March 8) in the Journal of Neuroscience, found the unusual beep triggered an immediate response followed by a second response around 200 milliseconds – or a fifth of a second – later. The initial response was from the basic auditory system, which recognised that it had heard a beep, and was the same in the patients and healthy volunteers.
The second response, recognising that the beep was unusual, was much smaller among those with dementia, demonstrating that the brains of the healthy volunteers were better at recognising that something had changed.
Examining which brain areas had been activated during the task and how they were connected up, the researchers combined their data with that from MRI scans that show the structure of the brain.
This showed damage to ‘multiple demand networks’ in the brain was associated with the reduction in the later response.
“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,” said Dr Cope.
“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.”
Multiple demand networks are found both at the front and rear of the brain. They do not have a specific task but are involved in general intelligence, such as problem-solving.
Highly evolved, such networks are found only in humans, primates and more intelligent animals, enabling us to be flexible in our environment.
The auditory system in healthy volunteers relayed the information to the multiple demand network to be processed and interpreted.
The researchers say the network then ‘reported back’ to the auditory system, instructing it on whether to carry on its work or to attend to the sound.
Dr Cope, a fellow of Murray Edwards College, said the research, while not pointing to any treatments that can alleviate symptoms, does reinforce advice given to dementia patients and their families.
“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.”
The findings could also help explain similar phenomena experienced by those living with other conditions where brain networks can become disrupted, such as schizophrenia, although this was not examined in the study.
The research was funded by the Medical Research Council and National Institute for Health Research, with support from Wellcome, the Biotechnology and Biological Sciences Research Council and the James S McDonnell Foundation.
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