Beyond memory loss: Rare dementia steals our ability to care

SOLNA, Sweden — When we witness someone in pain – a child skinning their knee, a friend burning their hand on a hot pan – our brains automatically respond with patterns of activity that help us understand and share their experience. This ability to feel what others feel is fundamental to human connection. But for people with behavioral variant frontotemporal dementia (bvFTD), this basic neural response gradually disappears, fundamentally changing how they relate to others’ emotions.

Now, new research explains exactly how this happens in the brain. Scientists at the Karolinska Institutet and Lund University have mapped the neural disruption that occurs in people with bvFTD by observing their brain activity during a carefully designed empathy task. The study, published in JAMA Network Open, marks the first detailed look at the biological basis of empathy loss in these patients.

To understand how the researchers tracked empathy in the brain, imagine watching someone accidentally touch a hot stove. Your instinctive wince is driven by specific neural networks that process others’ pain. These networks involve multiple brain regions working together, much like musicians in an orchestra creating a complex symphony of emotional understanding. The researchers wanted to see what happens when this neural orchestra loses some of its key players.

Using functional magnetic resonance imaging (fMRI) – a technology that tracks brain activity by measuring blood flow changes – the research team studied 28 patients with bvFTD and 28 healthy individuals of similar age and education. They showed participants two types of images: hands being touched harmlessly by a Q-tip and hands being pricked by a needle. This simple but elegant experiment allowed them to isolate and observe the specific brain networks that activate when we witness others in pain.

The results revealed a dramatic difference between the two groups. In healthy participants, viewing the painful images activated 12 different brain regions, creating a complex network of empathetic responses. These regions showed increased blood oxygen levels – essentially requiring more energy as they worked to process the emotional experience. However, in bvFTD patients, only two regions showed increased activity, suggesting a fundamental disruption in how their brains process others’ pain.

“What is particularly interesting is that we have been able to relate this measure of brain activity in patients to how carers rate their lack of empathy,” says lead researcher Olof Lindberg in a statement. “There turned out to be a strong correlation, and that’s important. It shows that what happens in the brain is connected to the people’s behavior.”

This finding helps explain one of bvFTD’s most distinctive features. Unlike typical dementia, which primarily affects memory, bvFTD targets the frontal and temporal lobes – regions crucial for personality, behavior, and emotional processing. This makes diagnosis particularly challenging because early symptoms can resemble other conditions where empathy is impaired, such as certain psychiatric disorders.

“This captures a key symptom in patients, and with a lack of empathy, it naturally becomes more difficult to act socially. So, it can affect the judgment of whether to be cared for at home, for example,” Lindberg explains.

The research revealed an important nuance: while emotional empathy – our automatic feeling response – was significantly reduced in bvFTD patients, their cognitive empathy remained relatively preserved. In other words, patients might still understand intellectually that someone is in pain, even if they don’t experience the usual emotional response to witnessing it.

In Sweden, where this research was conducted through a collaboration between three major hospitals, bvFTD affects approximately 3% of new dementia cases annually. While this percentage might seem small, its impact on patients and families is profound. When someone loses the ability to emotionally connect with others’ experiences, it changes the fundamental nature of their relationships.

For families and healthcare providers, understanding the biological basis of these changes offers valuable insights. Knowing that empathy loss stems from measurable changes in brain function helps explain behaviors that might otherwise seem puzzling or hurtful. This understanding could lead to better diagnostic tools and more effective strategies for managing the social and emotional aspects of the condition.