Groundbreaking research by researchers at the University of Oxford and NIHR Oxford Health Biomedical Research Centre revealed how serotonin shapes human behavior in the context of negative information.
The researchers reported that under conditions of elevated serotonin, subjects showed attenuated sensitivity to punishing outcomes, such as the loss of money due to a particular response during a game, but their sensitivity to rewarding outcomes was relatively unaffected. The findings suggest a crucial role for serotonin in helping subjects adjust their behavior when exposed to negative stimuli.
These findings do shed new light on how serotonin shapes human behavior, particularly in negative environments,” said lead author Michael Colwell of Oxford’s Department of Psychiatry. Colwell feels that this is where this research could help in offering some valuable insights into the roots and treatment of depression.
In sharp contrast to conventional antidepressants, which are SSRIs, the researchers adopted a completely novel approach using a selective serotonin-releasing agent. The level of serotonin went up directly in the human brain under the effect of a drug already being used against an ultra-rare form of epilepsy known as Dravet Syndrome.
This new information is important, says Professor Catherine Harmer, Professor of Cognitive Neuroscience at the University of Oxford and OH BRC Theme Lead for Depression Therapeutics. “Despite nearly a century of research, our understanding of how serotonin influences human behavior has remained unclear and controversial.” If serotonin does have a role in altering behavior, then it may maybe more to do with processing negative experiences than about enhancing positive experiences, according to Harmer, contesting the popular view of serotonin as the “happy chemical.”
Associate Professor Susannah Murphy from the University of Oxford commented that the study also puts forward the idea from the earlier work that the role of serotonin is implicated in cognitive processes requiring effort, for example, controlling unwanted behaviors. This finding could at least partially explain why drugs changing levels of serotonin are effective treatments against a broad array of mental disorders, from major depression to anxiety and obsessive-compulsive disorder.
This study involved 26 subjects treated with the serotonin-enhancing drug, with a control group of 27 participants who performed implicit learning and behavioral control tasks, after which participant behavior was fitted using state-of-the-art models.
The paper, “Direct serotonin release in humans shapes aversive learning and inhibition,” published in Nature Communications, may give new insight into the brain reward system function through serotonin’s complex role in human behavior and mental health.
This work deepens our knowledge of the functions of serotonin but opens new perspectives in developing more effective treatments against mental health disorders.