When it Comes to Striatal Dopamine: Nature or Nurture?
Researchers have found that genetics and environmental experience affect dopaminergic function in different parts of the human striatum.
-- by Nina Lincoff
Nature or nurture is a common question in all forms of science, including neuroscience. Striatal dopamine is an important neurochemical that affects behavior and neuropsychiatric disorders. In healthy populations, dopaminergic function is associated with personality traits, social status, and cognitive function. For less healthy individuals, it can correspond with disorders like schizophrenia and addiction. Human striatum are affected by striatal dopamine and consist of three areas: the limbic striatum, which is associated with reward and motivation, the associative striatum, which affects memory and executive function, and the sensorimotor striatum, which is associated with movement. With psychiatric disorders like schizophrenia and addiction, nature and nurture associations of dopamine are key for understanding the root of the disease.
In a recent study published by the American College of Neuropsychopharmacology, researchers found that inherited striatal dopamine characteristics are strongest in the sensorimotor striatum, while individual environmental factors show greatest effect in the limbic striatum. The results of the study suggest that dopaminergic function is, indeed, subject to "nurture."
The Expert Take
“One of the most surprising aspects of our study was that the effect of genes and environment on dopamine function could be so different depending on which part of a relatively small but important area of the brain, called the striatum, that you looked at,” said study author Paul Stokes, M.B., Ch.C, B.Sc.
Previous studies have shown that the limbic area of the striatum is important for addictions and reward, and that the sensorimotor part for habit formation. “Our study confirms that individual environmental effects—such as everyday experiences in adolescence and adulthood—have a strong influence over limbic dopamine function and that genetic inheritance strongly influences sensorimotor dopamine function,” said Stokes.While one might expect that shared experiences for twins also affect dopaminergic function, Stokes said that is not the case.
“These results help us to better understand how everyday experiences and genetics can influence dopamine function, which is key to disorders such as addictions and schizophrenia,” said Stokes.
Source and Method
Monozygotic (MZ) twins are genetically identical, and provided the best population for study of environmental factors on the biological dopamine system. Dizygotic (DZ) twins were also observed, but only share about 50 percent of genetic material. Nine MZ and 10 DZ same sex twin pairs were observed in the study. Each twin underwent one [18F]- DOPA PET scan, and those results revealed that a combination of individual-specific environmental factors account for 56 percent of striatal dopamine function. This implies that "nurture" can affect dopaminergic function.
Different parts of the human striatum, a very important part of the behavioral brain, react to different dopaminergic functions. Genetic striatal dopamine affects the sensorimotor striatum, while individual environmental factors affect the limbic striatum. Brain moderation of movement is therefore more likely to be affected by hereditary striatal dopamine, while reward and motivation neurological structures are more likely affected by individual environmental experiences.
“There have only been two twin studies looking at the effects of genes and environment on human brain chemical systems – one for the serotonin system and ours,” said Stokes. “We would suggest that it is important for further twin studies to be done looking at how genes and environment effect dopamine release in the brain.”
A previous study on striatal dopamine found that it affects specific reversal learning.