A neuroimaging study found that men and individuals with psychiatric symptoms who experience more pronounced anhedonia tend to have increased functional connectivity between the paraventricular nucleus of the thalamus and the nucleus accumbens—two brain regions involved in reward processing. The paper was published in the Journal of Affective Disorders.
Anhedonia is the inability to experience pleasure or enjoyment from activities that were once found enjoyable, such as hobbies, social interactions, or food. It is a common symptom of mental health conditions like depression, schizophrenia, and posttraumatic stress disorder. People with anhedonia often feel emotionally numb, disconnected from others, and struggle with motivation. Anhedonia can be classified into two types: social anhedonia, which affects relationships, and physical anhedonia, which impacts sensory pleasures.
The condition is linked to dysfunctions in the brain’s reward system, primarily involving neurotransmitters such as dopamine and serotonin. One brain region particularly linked to anhedonia is the nucleus accumbens, which plays a critical role in experiencing pleasure and learning associations with pleasant stimuli. An interplay between neurons that use dopamine for signaling and specific opioids produced by the body (endogenous opioids) in the shell of this region appears to play a key role in the perception of pleasurable experiences.
Study author Bianca T. Leonard and her colleagues sought to explore the role of another brain region in anhedonia—the paraventricular nucleus of the thalamus. This region is functionally connected to the nucleus accumbens and other areas involved in processing emotions. The researchers conducted a neuroimaging study focusing on the functional connectivity of the paraventricular nucleus in individuals with varying levels of anhedonia.
The study included 63 adult participants, 47 of whom were experiencing psychiatric symptoms. Their mean age was 23–24 years, and 48 participants were women.
Participants underwent resting-state magnetic resonance imaging (MRI) of their brains. They also completed assessments for depression and anxiety using the Beck Depression Inventory and the Beck Anxiety Inventory. From these assessments, the researchers derived a measure of anhedonia using statistical analysis.
The results showed that functional connectivity between the paraventricular nucleus of the thalamus and the nucleus accumbens was positively associated with anhedonia in men with psychiatric symptoms. In other words, men with psychiatric symptoms who had greater functional connectivity between these two brain regions tended to have more severe anhedonia symptoms.
A similar but weaker finding was observed when the researchers analyzed individuals with psychiatric symptoms regardless of gender and when they examined men only. The association was of moderate strength in men. However, this association was not found in individuals without psychiatric symptoms, in the subgroup of women, or in the overall sample.
“The results of this study suggest that there is a pattern of functional connectivity between the PVT [paraventricular nucleus of the thalamus] and reward processing regions that is shared among males experiencing anhedonia. This pattern may reflect an important role that the PVT to NAc [nucleus accumbens] communication is playing in decision-making and behavioral changes in anhedonia,” the study authors concluded.
The study sheds light on the neural underpinnings of anhedonia. However, it should be noted that the study was conducted on a relatively small group of young people. Additionally, it did not use a dedicated measure of anhedonia but instead derived the assessment from measures of depression and anxiety.
The paper, “Anhedonia is associated with higher functional connectivity between the nucleus accumbens and paraventricular nucleus of thalamus,” was authored by Bianca T. Leonard, Sarah M. Kark, Steven J. Granger, Joren G. Adams, Liv McMillan, and Michael A. Yassa.
