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Study reveals deficiencies in social signals in frontotemporal dementia

UCL researchers have found shrinkage of regions in the brain causes loss of emotional awareness in frontotemporal dementia patients.

When patients with frontotemporal dementia were shown videos of emotional facial expressions, they were unable to identify the emotion being displayed. The study shows that the loss of this awareness is caused by shrinkage of several regions of the brain. It also explains why patients often develop a ‘poker face’ that makes other people uneasy in social situations.

Healthy individuals automatically imitate the facial expressions of those they interact with, which helps us to work out what other people are feeling. The mimicry is done both involuntarily and unconsciously, but these subtle facial movements create a ‘social resonance’ that helps us to bond with other people.

The study was conducted by playing videos of emotional facial expressions to people with frontotemporal dementia, and to participants without dementia. Electrical activity in the muscles of their face were measured, as they watched the videos, to measure how much they were imitating the expression. After each video they had to say what they thought the emotion was (e.g. anger, fear, disgust, happiness, surprise). They then had a detailed MRI brain scan, which researchers could use to work out which areas of the brain which had shrunk more in those who imitated the emotions less.

Dr Charles Marshall, lead author on the paper, said: “We found that patients with frontotemporal dementia had loss of the normal automatic imitation of facial expressions. We also showed that some people with frontotemporal dementia had problems using the movement of their face to identify which emotion they were seeing. Using brain scans, we were able to show that this is caused by shrinkage of several brain regions, including those responsible for processing the facial movements of others and for moving our own faces”.

Dr Marshall suggested that the study shows an entirely new mechanism for the loss of emotional awareness and difficulties with social interaction that are such a major problem in frontotemporal dementia.

The results from the study will allow for better diagnosis and tracking of the disease in patients. It also means that the responses to possible treatments can be measured.

To read the full paper see Scientific Reports.