Dementia symptoms vary, but they can include issues with memory, speech, behavior, or vision. However, one characteristic common to all types of dementia is a problem reacting to unexpected situations.

In people with dementia, damage to brain areas known as “multiple demand networks,” highly developed parts of the brain that promote general intelligence, makes it difficult for them to adjust to changes in their environment. This is according to Cambridge University experts.

Different kinds of dementia, like Alzheimer’s disease and frontotemporal dementia (FTD), cause toxic proteins to build up in different parts of the brain. This can make it hard for people to remember things or do things that used to be easy. This means that dementia symptoms vary and may include difficulties with memory, speech, behavior, or vision. However, one symptom common to all types of dementia is a problem reacting to unexpected situations.

“At the heart of all dementias is one core symptom, which is,” according to Dr. Thomas Cope, “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 looked at data from 75 individuals who all had one of four varieties of dementia that impacted distinct parts of the brain to figure out why this occurred. The patients, along with 48 healthy controls, listened to various noises while a magnetoencephalography machine measured the tiny magnetic fields produced by electrical currents in the brain. These technologies, unlike typical MRI scanners, provide for extremely exact timing of what is happening in the brain and when it is happening.

During the scan, the participants listened to a series of beeps while watching a silent film – David Attenborough’s Planet Earth. The beeps followed a consistent pattern, but every now and then one would be different, for example, with a higher pitch or volume.

The researchers discovered that the odd beep elicited two responses in the brain: an instant response and a second response 200 milliseconds later (a fifth of a second).

The fundamental auditory system was the first to respond, recognizing that it had heard a beep. Both patients and healthy participants had the same reaction.

The second answer, on the other hand, recognized that the beep was out of the ordinary. This response was significantly lower in dementia patients than in healthy participants. In other words, the brains of healthy people were better at recognizing when something had changed.

The researchers looked at which brain areas were stimulated and how they were connected during the task, then merged their findings with data from MRI scans, which depict the brain’s structure. They discovered that damage to the brain’s ‘multiple demand networks’ was linked to a decrease in the later response.

Multiple demand networks, which can be located in both the front and back of the brain, are parts of the brain that are engaged in general intelligence, such as problem solving. They are highly evolved and can only be found in humans, primates, and higher-level creatures. These networks enable us to be adaptable in our surroundings.

The auditory system in healthy individuals picks up sound, which is relayed to the multiple demand network to be processed and interpreted. The network then’reports back’ to the auditory system, telling it whether or not to continue listening or to pay attention to the sound.

“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,” adds 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.”

While the study does not suggest any treatments to ease the discomfort, Dr. Cope believes it validates recommendations provided 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.”

Despite the fact that their study only looked at dementia patients, the findings may explain comparable phenomena seen in people with schizophrenia, where brain networks can become disturbed.

Source: 10.1523/JNEUROSCI.1622-21.2022

Image Credit: Getty

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