A new study from the University of Birmingham has found a connection between the neurotransmitter dopamine and the mentalising abilities of healthy individuals.
Mentalising describes the act of attributing and understanding the mental states — or thoughts and feelings — of oneself, as well as others.
The results, published in PLOS Biology, indicate that a change in dopamine levels can significantly affect the mentalising abilities of healthy adults.
The study
In the double blind, placebo-controlled study, 33 healthy volunteers were given haloperidol, a drug which blocks dopamine receptors in the brain.
The participants took part in the same set of experiments on two separate days, though on one of those days, they were given a placebo.
Participants were asked to complete an animations task, where they were shown videos of triangles 'interacting' with each other. They were then asked to assess the videos and select a label that best described the scene.
The researchers also investigated how successfully participants could judge emotions depicted by whole-body point light displays.
The results
After taking haloperidol, participants were significantly less able to detect mental states. This was due to the effects of the drug on emotional recognition.
The role of dopamine in the body
Dopamine is a chemical messenger present in the brain that plays a role in pleasure, motivation and learning.
It's also known that low dopamine levels in the regions of the brain that influence movement underpin many of the symptoms associated with Parkinson's disease.
A dopamine imbalance also affects individuals’ socio-cognitive abilities
As well as issues with movement, Parkinson's is associated with socio-cognitive problems, such as difficulties with emotion recognition or mentalising. However, no definitive link has been made between these problems and dopamine imbalances.
More commonly, in fact, theory of mind difficulties have been associated with psychosocial changes such as isolation and social withdrawal that are a common feature of dopamine-related disorders.
The lead author, Dr Bianca Schuster said: “While the mentalising abilities of people who are struggling with Parkinson’s may not be the main focus of treatment, it nonetheless has a huge impact on people with the disease. Gaining a better understanding of how dopamine imbalances may affect mentalising processes in the brain could therefore be really significant for individuals, as well as gaining a better understanding of the secondary effects of the drugs prescribed for Parkinson’s and other disorders.”
“The main implication of our work is that in disorders with dopamine dysfunctions, in addition to producing the primary symptoms associated with these disorders (such as motor symptoms in Parkinson’s disease), the dopamine imbalance also affects individuals’ socio-cognitive abilities” added Dr Schuster. “This work could have implications for the way in which we treat Parkinson’s in the future, but also the way in which we use any drugs which affect the action of dopamine in the brain.”