Early-Onset Dementia Associated With Loss of Pleasure, Mental Health Issues As 'Hedonic Spots' Fades Away

Dementia takes people's memories away, while some other forms rob patients of their inhibition and happiness. It is often mistaken for depression but a new study suggests otherwise.

The study, entitled "Uncovering the prevalence and neural substrates of anhedonia in frontotemporal dementia" published in the journal Brain, found that some forms of early-onset dementia are associated with loss of pleasure that is linked to the hedonic spots that control reward-seeking behavior.

The Australian study discovered the cause of this inability to feel pleasure in people with early-onset dementia, EurekAlert! reported. Researchers said that it is related to marked degeneration or atrophy in frontal and striatal areas of the brain that are linked to diminished reward-seeking in frontotemporal dementia (FTD) patients.

They noted that this is the first study to demonstrate profound anhedonia, the clinical term for the loss of ability to experience pleasure.

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Early Onset of Dementia Associated With Loss of Pleasure As 'Hedonic Spots' Fades Away

Anhedonia in Patients With Dementia

Anhedonia is a common symptom of mental health conditions, like depression and obsessive-compulsive disorder (OCD). Unlike most people, those suffering from anhedonia do not experience satisfaction after being rewarded or feel the excitement and bliss when achieving a goal or when with a loved one.

Since it is most often mistaken as depression, researchers from the University of Sydney and the University of New South Wales in Australia conducted a study on how anhedonia is linked to some types of dementia, ScienceAlert reported.

Muireann Irish, a neuroscientist from the University of Sydney, said that most of the human experience is motivated by the drive to experience pleasure although most people take it for granted. But losing the ability to seek and feel pleasure implies that a person is affected by neurodegenerative disorders.

The study had 121 participants wherein 87 of them has one of three forms of frontotemporal dementia FTD, early-onset dementia, with symptoms starting between ages 40-65.

The first type of FTD messes up the frontal lobe that controls the personality and emotional responses, while the second type strikes the temporal lobe that controls reading and comprehension. The third variant presents itself as a form of aphasia wherein patients would have reduced capacity in communicating through speech.

Comparing the data they gathered versus those gathered using similar evaluations with 34 Alzheimer's patients, the researchers found that those with the first variant of FTD are less likely to feel pleasure. The findings suggest that these patients feel less joy than before being diagnosed with FTD compared to those with the third variant or Alzheimer's disease.

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Brain's Pleasure and Reward System

The brain's pleasure and reward system is a "well-developed mesocorticolimbic circuitry, and serves adaptive functions," according to NCBI.

In the study's case, researchers were able to map the tissue densities of the participants and found loss of neurons in the orbitofrontal and prefrontal cortices, insular cortex, and putamen, brain regions that are linked to the pleasure and reward system.

Notably, the atrophy linked to anhedonia was distinct from the changes in people with depression or apathy. Researchers believe that their findings could help doctors better diagnose patients and could someday aid in the treatment of disease.

Irish added that their study also reflects the workings of complex neural networks that could be essential for future studies in addressing anhedonia on everyday activities, and to improve interventions on improving quality of life to patients and their families.