Scientists from Temple University and the University of Oregon have found that in people who experienced emotional abuse or neglect in childhood, difficulty anticipating joy may be linked to how the hippocampus works - a brain region responsible for memory and response to novelty. The study was published in The Journal of Neuroscience.
The subject is anhedonia - a reduced ability to experience pleasure or a lack of motivation for enjoyable activities. Psychologists divide it into two types: "consummatory" (a person feels no joy during an enjoyable activity) and "anticipatory" (a person does not expect pleasure and does not strive for it in the future).
The study involved 92 people aged 18 to 30 (average age about 21) who underwent resting-state brain scans, and 80 people who completed a task during scanning. Participants filled out questionnaires about childhood trauma (emotional abuse, emotional neglect, physical neglect before age 16) and about the ability to anticipate and experience pleasure.
The scientists measured activity in the anterior hippocampus and its connectivity with two key areas of the reward system - the ventral tegmental area (a cluster of dopamine-producing neurons) and the nucleus accumbens (a structure that processes reward and motivation). Participants also performed a task of finding a target image among familiar and novel landscapes, which allowed the hippocampus response to novelty to be assessed.
It turned out that in people with a higher level of childhood trauma (one standard deviation above the mean), weaker hippocampal connectivity with the nucleus accumbens at rest, as well as a reduced hippocampal response to new images and weak signal transmission from the hippocampus to the ventral tegmental area, were associated with more pronounced anticipatory anhedonia. In participants with low trauma levels, no such associations were observed. None of the brain measures was associated with "consummatory" anhedonia.
According to the authors, the results are consistent with animal data in which stress weakened hippocampal connections with the nucleus accumbens and reduced reward seeking. However, the study is cross-sectional (all data were collected at a single point in time), so it does not prove that trauma or brain changes directly cause anhedonia. It is possible that baseline differences in brain function make some people more vulnerable to the effects of stress. In addition, participants recalled their childhood from memory, and questions about physical and sexual abuse were excluded because of ethical restrictions. The sample was also drawn from a project studying psychosis risk, and 22 people met criteria for clinically high risk, so results may differ in the general population.
The scientists emphasize: early stress may increase vulnerability to anhedonia, but engagement of circuits linked to novelty and exploratory behavior may reduce this risk. The long-term goal is to understand how these mechanisms relate to subjective experiences and memories.