Parkinson’s Disease is a progressive neurological disorder affecting 1 in every 500 people in the UK. The most noticeable symptoms of the disease involve problems with movement, such as impaired balance, slowness and stiffness of movements, or tremors. However, Parkinson's is more than just a movement disorder. There is a body of work describing non-motor symptoms, which often cannot be treated with Parkinson's medication. These include, for instance, problems with mood, such as depression and anxiety, sleep disorders or problems with concentration.
People with Parkinson’s also frequently report having difficulties with their social interaction. In the SPiEs study we aimed to investigate whether people with Parkinson’s have difficulty in recognising the emotional expressions of others and whether this difficulty is linked to the progression of the disease.
We invited 20 participants aged 50 or older with Parkinson's to take part in the study. To measure whether difficulties with recognising emotional expressions can be attributed to normal ageing or to Parkinson's disease, we also invited 20 participants of a similar age, gender and education level, who do not have the disease, to act as ‘control’ participants. Some of our control participants were spouses or friends of participants with Parkinson's, and some were members of Voice North. We are extremely grateful to the Voice North members for their help and commitment to the study!
All participants went through rigorous and lengthy testing, where we first assessed their memory, attention and mood. Next, we measured how good each participant was at recognising subtle facial expressions of anger, disgust, fear, happiness, sadness and surprise, in an specially designed computer-based experiment. In the emotion recognition task, photographs of faces showing emotional expressions, sometimes very subtle and other times more obvious, were flashed on a computer monitor very briefly. Participants were asked to rely on their first impression when deciding whether the face showed the emotion or not. We ran multiple repetitions of this task for all participants to get a robust and stable measure of their performance. Next, we made the task even more difficult by inverting the face photographs and testing whether participants could still recognise emotions from the upside-down expressions. In the final challenge, participants were recognising emotions from split faces, also known as chimeric faces. Chimeric faces are artificially created faces where one half of the face shows a neutral expression and the other shows an emotional expression. They are often used by psychologists to test brain lateralization – whether one of the brain hemispheres (left or right) is better at recognising emotions. You can see an example of face photographs showing different intensities of happiness in full (top) and split (bottom) faces in the image above.
To date we have tested 19 people with Parkinson’s (6 women and 13 men) with an average age of 59, an additional 5 people with Parkinson’s who also experience memory problems (all men) with an average age of 73, and 19 people without Parkinson’s (13 women and 6 men) with an average age of 65.
We found that all participants were able to recognise all of the emotions, but some found it more difficult than others. On average, participants with Parkinson’s found it more difficult to recognise emotions of happiness, sadness and surprise than control participants. Participants with Parkinson’s who also experience memory problems found the task even more challenging and showed difficulty in recognising all 6 emotions. Additionally, participants with Parkinson’s found it more difficult to recognise emotions from upside-down faces. We think this might be because people with Parkinson’s often experience difficulties in other visual tasks such as judging distances3.
There are still a few months of work on the SPiEs study ahead of us. We are hoping to test more people with Parkinson’s who experience memory problems to get a better understanding of how the ability to recognise the emotions of others is related to cognitive decline. The contribution and help of all our participants to date has been exceptional. It has allowed us to understand how important it is to take into account individual differences when measuring ones ability to recognise emotions. This is what distinguishes the SPiEs study from other similar studies and makes it so timely. We would like to once again thank all our volunteers for their dedication and we hope to share the final results of the study soon.