Does Huntington's disease disrupt the amygdala before symptoms?
People carrying the Huntington's gene showed weaker coupling between the amygdala and the face-processing area of the brain while seeing angry faces, and this weakening was greater the closer they were to predicted disease onset.
Source
The role of the amygdala during emotional processing in Huntington's disease: from pre-manifest to late stage disease
Study at a glance
- Design
- Case-control — Two cross-sectional group comparisons: fMRI with amygdala PPI connectivity (gene carriers vs controls) and an eyes-based social cognition test across disease stages.
- N
- Study 1 (fMRI): 20 pre-manifest gene carriers and 23 controls. Study 2 (RMET): 29 pre-manifest carriers, 50 manifest patients and 26 separate controls; 11 people took part in both.
- Population
- Adults carrying the Huntington's disease gene (pre-manifest and manifest at all stages) and healthy controls from a UK clinic
- Outcome
- Amygdala functional connectivity during implicit angry-face processing; Reading the Mind in the Eyes Test score
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
In the first study, 20 pre-manifest gene carriers and 23 controls did a simple face-or-house button task in an MRI scanner while angry and neutral faces appeared without them being told about the emotions; the researchers measured how activity in the left amygdala co-varied with the rest of the brain for angry versus neutral faces. In the second study, 29 pre-manifest carriers, 50 patients at early, moderate or late stage, and 26 controls did the Reading the Mind in the Eyes Test, which asks people to judge mental states from photographs of eyes.
What they found
Carriers and controls did the scanner task equally fast and accurately, but carriers showed weaker amygdala-to-right-fusiform connectivity, and weaker connectivity went with being closer to estimated onset (r = 0.45). Eyes-test scores fell steadily with disease stage; pre-manifest carriers as a group did not differ from controls, but their scores dropped as predicted onset approached. In a small subgroup tested on both tasks within a year, connectivity and eyes-test performance were strongly correlated (r = 0.77).
The limits
What it doesn't show
The samples were small and the connectivity difference only survived a more lenient statistical threshold than the whole-brain analysis, as the authors admit. Both studies are cross-sectional, so they show stage-related differences rather than tracking decline within the same people. The link between connectivity and the eyes test rests on only a handful of people, after two were removed, and emotion recognition itself was never tested in the carriers; mood, executive function and age effects were not fully controlled.
Key terms
- Pre-manifest gene carrier
- Someone who has inherited the Huntington's mutation but does not yet show the motor signs needed for a clinical diagnosis.
- Psychophysiological interaction (PPI)
- An fMRI analysis that asks whether two brain regions become more or less coupled in one task condition compared with another.
- Fusiform face area
- A region on the underside of the temporal lobe that responds strongly to faces.
- Reading the Mind in the Eyes Test
- A theory-of-mind task in which people choose which word best describes the mental state shown by a pair of eyes.
- Implicit emotion processing
- Processing of emotional content when the task does not ask the person to attend to or judge the emotion.
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Quiz yourself
Which pair of regions showed reduced coupling in pre-manifest carriers during angry faces?
Common questions
Why ask people to judge face versus house rather than name the emotion?
An implicit task keeps performance equal across groups, so any difference in brain activity is less likely to reflect people simply doing the task worse.
Does this prove the amygdala causes social problems in Huntington's disease?
No. It shows correlations between reduced amygdala connectivity, poorer eyes-test performance and closeness to onset, but a causal role would need longitudinal or intervention evidence.
Why was the eyes test used at all?
The authors used it as a practical bedside stand-in for amygdala function, because people with amygdala lesions are known to perform poorly on it.
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