Inside the Brain’s Theme Park: How Huntington’s Disease Disrupts the Emotion Coaster

Welcome to Brainland, the bustling, 24/7 theme park in your head. There’s Memory Maze, Logic Log Flume, and of course, the Emotion Coaster, where your brain races through tracks themed around happiness, sadness, and anger. However, for some people who carry the gene for Huntington’s disease (HD), some of these rides start acting up long before the big attractions like Movement Mountain or Memory Maze show signs of trouble. Strangely, even when everything else seems fine, the Emotion Coaster may begin to stall, especially on the tracks of anger, sadness, and fear. 

This isn’t a theme park glitch; it’s real science, explored by Dr. Shahin Nasr and his team at Massachusetts General Hospital and Harvard Medical School. 

When the Emotion Coaster Goes Off Track

Most of us don’t think twice about reading someone’s face. A smile reflects happiness. A furrowed brow? Maybe anger. It’s automatic, like muscle memory because our brains are wired to pick up on emotional signals. But what happens when the brain can’t understand how others feel?

Reading facial expressions is crucial because it helps us navigate daily social life. It helps us understand how others feel, respond with empathy, and avoid misunderstandings. Whether it’s noticing a friend’s sadness behind a smile, picking up on a colleague’s confusion in a meeting, or sensing when to give someone space, facial cues guide how we connect, communicate, and make social decisions every single day. 

When this ability fades, as it can in HD, relationships can suffer. This is not because people with HD don’t care, but because they may struggle to understand emotional expressions in other people, a skill which many take for granted.

Buckle Up for the Emotion Tracks

Dr. Shahin Nasr and his team ran an important study on emotion recognition in people with pre-manifest HD. ‘Pre-manifest’ HD refers to people who have tested positive for the gene that causes HD (CAG number is 40 or more), but they do not yet display any recognisable symptoms (equivalent to HD Integrated Staging System (HD-ISS) Stage 0). 21 people with pre-manifest HD and 16 people who did not have HD were recruited in this study. 

Each participant was shown 70 different photographs of people. These photographs displayed different facial expressions reflecting different emotions, including happiness, anger, sadness, fear, surprise, disgust, and ‘neutral’ faces. Participants were provided with name cards for each emotion. The task was simple, choose one name card that best identifies the emotion being shown in the photograph.

Interestingly, the participants with pre-manifest HD were less accurate at recognising anger, sadness, and fear from facial expressions displayed in the photographs compared to the control group. These early struggles to recognise particular emotions from other people’s faces suggests that even during the pre-manifest stage of HD, the inner ability to read negative emotions (anger, sadness, and fear) may already be decreasing.

Under the Hood of the Emotion Coaster

To dig deeper, a smaller sub-group of participants had their brains scanned using functional MRI (fMRI) while they looked at images of faces showing different emotions (neutral, happy, and angry). 

Think of the brain scans like a theme park map that shows which rides are busiest. But instead of tracking people, it shows which parts of the brain are most active, based on where the blood flows. Dr. Nasr and his team wanted to see what was happening in the brain while participants looked at faces reflecting different emotions. Specifically, how busy the Emotion Coaster was in people with pre-manifest HD (meaning the brain area that helps us understand facial expressions in other people).

When this ability fades, as it can in HD, relationships can suffer. This is not because people with HD don’t care, but because they may struggle to understand emotional expressions in other people, a skill which many take for granted.

Interestingly, there is one particular region of the brain that helps us to understand what someone is feeling or thinking by looking at their face, body, or tone of voice. However, in people with pre-manifest HD, this area of the brain showed reduced activity. This wasn’t just about having difficulty seeing faces clearly or understanding faces in general. It was more like the Emotion Coaster wasn’t working properly, making it harder for people with pre-manifest HD to understand emotions through facial expressions in other people.

Fixing the Emotion Coaster Before It Breaks Down

These findings are important because they show that small changes in the brain can happen early, even before movement symptoms begin. This can affect how people with pre-manifest HD understand emotions through facial expressions in other people.

However, this isn’t just something interesting to note. If people with pre-manifest HD have trouble reading emotions, it can cause big problems in relationships, work, and mental health. They might not react the right way in tense situations, which can lead to fights, feeling alone, or more stress.

This research gives us hope. By spotting early warning signs, such as changes in brain activity, we may be able to better support emotional and cognitive health, in people with pre-manifest HD before other symptoms appear.

End of the Ride

HD doesn’t just appear overnight, it starts gradually, with little changes that may be easy to miss. This study highlights that one of the earlier signs of HD might be in how we understand facial expressions in other people. For example, spotting a frown, a worried look, or a hint of anger.

Dr. Nasr and his team confirmed that a specific part of the brain which is important in understanding emotions by looking at facial expressions, was not as active in people with pre-manifest HD. This is equivalent to spotting a problem on the Emotion Coaster, before it fully breaks down.

It is important to remember that this study is more than just science, it’s a step towards changing lives for people with HD. By spotting very early brain changes linked to emotion recognition, this is not just identifying a faulty ride, it is uncovering a potential early warning sign of HD. The earlier we see the signs, the sooner we can act. It also provides us with a chance to support the daily interactions for people with pre-manifest HD, protect their relationships and even their quality of life.

TL;DR

• Emotion Coaster Starts to Wobble Early – Even before classic HD symptoms like movement or memory issues appear, people with the gene may struggle to recognise facial expressions showing anger, sadness, or fear.
• Study in Pre-manifest HD Shows Reduced Accuracy – In a study by Dr. Shahin Nasr, participants with pre-manifest HD were less accurate at identifying negative emotions in photos of facial expressions, suggesting early emotional processing changes.
• Brain Scans Reveal Decreased Activity – fMRI scans showed that brain regions involved in recognising others’ emotions are less active in people with pre-manifest HD, even though they had no visible symptoms.
• Real-Life Impact – This difficulty reading emotions can affect relationships, cause misunderstandings, and increase stress, not due to a lack of empathy, but reduced ability to interpret social cues.
• Early Detection = Early Support – Spotting these changes could help clinicians intervene earlier to support emotional wellbeing, social functioning, and quality of life before HD symptoms fully develop.
• Hope on the Horizon – This research adds to our understanding of HD progression and offers a potential early marker for future interventions targeting emotional and cognitive health.

Learn More

Original research article, “Are you angry? Neural basis of impaired facial expression recognition in pre-manifest Huntington’s” (open access)