Dementia is a thief who pockets a lot. In some ways, it requires our memories. Other forms rob us of inhibition. Sometimes it even takes away happiness.
A new study has shown for the first time how some forms of dementia that start early are associated with a huge loss of pleasure associated with wasting ‘hedonic hotspots’ – brain regions associated with reward.
An absence of pleasure is known as anhedonia, and it is a common symptom in mental health conditions such as depression and obsessive-compulsive disorder. Where most of us are rewarded with a sense of contentment, excitement and happiness when we reach a goal or associate with loved ones, those who experience anhedonia may not.
Interestingly, early dementia is often confused with depression, and that a decrease in motivation can be used as a criterion for diagnosis. Therefore, researchers from the University of Sydney and the University of New South Wales in Australia have decided to formally investigate the link between anhedonia and types of dementia, according to them for the first time.
“Much of the human experience is motivated by the pursuit of pleasure, but we often take this ability for granted,” says neuroscientist Muireann Irish of the University of Sydney.
“But think about what it might look like to lose the ability to enjoy the simple pleasures of life – it has strong implications for the well – being of people affected by these neurodegenerative disorders.”
In the study, the researchers assessed 121 patients diagnosed with different forms of dementia to determine who was more likely to suffer from the clinical symptom of anhedonia.
Of the group, 87 patients had 1 of 3 different types of frontotemporal dementia (FTD). FTD is a dementia that occurs earlier, with symptoms that usually start between the ages of 40-65.
One FTD variant affects the frontal lobe, confused with the personality and emotional responses of an individual. A second variant hits the temporal lobe and reduces the person’s reading and comprehension. The rarest of the three is a form of aphasia that reduces their ability to communicate through speech.
The team used several assessment tools to measure the prevalence of anhedonia in each subset of FTD as a single symptom and as a hallmark of depression and a general lack of motivation.
The results were compared with the results compared with similar evaluations done on 34 volunteers with Alzheimer’s and 51 otherwise healthy older participants.
They found that those with frontal and temporal forms of FTD – clinically referred to as behavioral variant FTD and semantic dementia – were much less likely to experience joy than before their diagnosis, compared with those with the rarer aphasia variant or Alzheimer’s. disease.
This finding was reflected in a mapping of the tissue density of the patients across their entire brain, which repeatedly revealed a loss of cells in areas such as the orbitofrontal and prefrontal cortical, insular cortex as well as the putamen. These regions are linked to the brain’s pleasure systems.
What was important was that the atrophy associated with anhedonia was different from the changes associated with apathy or depression.
Regions circled in green are associated with pleasure and reward. (University of Sydney)
The discovery may seem bleak, but it may help doctors better diagnose the disease and eventually treat it.
“Our findings also reflect the functioning of a complex network of regions in the brain, suggesting potential treatments,” says Irish.
“Future studies are essential to address the impact of anhedonia on everyday activities, and to inform the development of targeted interventions to improve the quality of life in patients and their families,” says Irish.
This research was published in Brain.