Behavioral changes in dementia: study follows evidence | Health

When most people think of dementia, particularly Alzheimer’s disease, the first thing they often think of is memory loss.

However, dementia changes a person’s behavior, be it making them restless or worried, melancholic, nervous or apathetic, or even changing their entire personality.

Over time, these behavioral changes can cause as much disruption in their lives as loss of their ability to think and remember effectively.

Now a team of researchers at the University of Michigan reports new clues about what might be happening in the brains of people who are already showing the first signs of behavioral changes associated with dementia.

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Using two types of advanced medical imaging, they examined the brains of 128 people in the early stages of dementia and showed links between one of the brain’s key communication networks, a protein called tau, and the level of a person’s behavioral symptoms.

This goes beyond the role of tau that scientists already knew about in people with advanced dementia: It causes tangled nerve fibers in brain regions involved in thinking and memory.

Results of the study:

The new study suggests that tau disrupts the integrity of the brain’s salience network. This pathway between specific brain regions is key to our ability to understand the things that happen around us and decide how to respond to them. It also helps us process our own thoughts and feelings.

The researchers showed that the more a person’s salience network was disrupted by the presence of tau, the more behavioral changes that person would experience. They report their findings in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

While the one-time imaging of these 128 research volunteers cannot show cause and effect, the strong connection between tau, disruption of the salience network and behavior change is intriguing, the team says.

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They call for further investigation of the potential connection in other populations and for research to assess changes over time, to examine what might be going on in the pathways of connected brain cells that make up the salience network, and to investigate how this is related to tau formation and behavioral changes over the years.

They also hope to test whether they can slow behavioral changes in people with early dementia by targeting the salience network with weak electric current or magnetic fields applied from outside the skull and controlled by precise imaging.

Researchers in the Research Program on Cognition and Neuromodulation Based Interventions (RP-CNBI) are led by Alexandru D. Iordan, Ph.D. and program director Benjamin M. Hampstead, Ph.D. Both are faculty members in the Department of Psychiatry at UM Medical School.

Iordan, a neuroscientist and lead author of the new study, says: “What we see is that presence-tau pathology is linked to behavioral symptoms that are not directly related, but rather arise from dysfunction of a specific network in the brain – the Salience.” The more this network is affected, the more severe the behavioral symptoms are.

He adds: “This is the first study to link an individual’s biomarker status to the dysfunction of this network and behavioral symptoms in people across the Alzheimer’s disease spectrum.”

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The team used functional magnetic resonance imaging (fMRI) to examine each volunteer’s brain and detect three different networks, each connecting distant areas of the brain. They used a measure called the network segregation index to measure how functionally independent each network was compared to other brain networks.

They combined the fMRI results with the results of a battery of neuropsychological tests and behavioral questionnaires that the volunteers took. They also examined results from positron emission tomography, or PET, scans, which showed whether the person’s brain contained excess tau protein as well as beta-amyloid, another protein linked to Alzheimer’s.

The salience network was the only one of the three networks whose level of integrity correlated with the presence of tau and the severity of dementia-related behavioral problems. The default mode network appears to be involved as a supporting actor. The third network examined, the so-called frontoparietal network, had no connection to behavioral symptoms.

The new study showed that, unlike tau, the presence of amyloid in the brains of some volunteers was not linked to problems in the salience network or the level of that person’s behavioral symptoms.

Iordan points out that the salience network is also known to play a role in some psychiatric disorders and in frontotemporal dementia, a type of early-onset, rapidly progressive dementia characterized primarily by behavioral and personality changes.

Iordan points out that PET scans for tau and amyloid are now being used clinically in the diagnosis of dementia and in treatment with new drugs aimed at reducing the formation of amyloid and thus slowing cognitive decline.

But blood tests that can also detect the presence of tau and amyloid and use them as biomarkers for the risk of dementia are now available. Because they are much less expensive than PET scans, they could also be useful for future studies of tau’s role in behavior change, he says.

Further research could also help explain and even predict differences in the onset of behavioral change in people with dementia and the pace of decline. It could also lead to ways to identify people whose behavioral changes are the earliest detectable sign of dementia risk, even before cognitive abilities change.

But the most exciting thing for Iordan and his colleagues?

“Our results provide us with a functional target for possible interventions,” he said. “Thanks to a larger study led by Dr. Hampstead, which studies the effects of different doses of weak electrical currents on the brain, we will soon be able to see whether brain stimulation changes these relationships.” This larger study is nearing completion and we are very excited to see what the results will show , so stay tuned!”

Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice. If you have any questions about a medical condition, always seek advice from your doctor.

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