It has long been known that the hormone dopamine plays a key role in both addictive and learning behaviors. As with all neurotransmitters, “normal” functioning of these small molecules in the body depends on their receptors, of which there can be several types.
Two papers, published last year in the journal Science, both focus on particular dopamine receptor types, and behaviors associated with them. Work from Jeffrey Dalley’s lab1 uses PET to demonstrate that impulsive rats have significantly lower availability of two dopamine receptor types in a certain brain area, and further, that such impulsivity predicts how effective cocaine is in reinforcing behaviors thatt cause its administration. Meanwhile, experiments conducted by Tilmann Klein2 indicate that people with a certain allele of one type of dopamine receptor are significantly less able to learn a task via negative feedback.
The latter work, however, has implications beyond the nature of learning. This is the first example of a certain type of human behavioral trait about which one can make quantitative predictions through genomic analysis. This trait is one that has the potential to stratify people; categorize them before birth according their potential abilities.
This gene presents the possibility for exactly the sort of genetic profiling that many have predicted with dread. The former work mentioned above carries some of the same baggage, a PET scan based screening of individuals could potentially be done quite early, and it is not hard to imagine the development of genetic screens to forecast “dopamine receptor availability.” An interesting conclusion to the presentation of these ideas would be some exploration of the actual value of being able to learn from negative feedback. Are those less able to learn in this way simply more bold? Fearless? Risk-takers? More creative? Could there be some value in attempting to tailor one’s activities to one’s genetic disposition?
Just as the construction of the atomic bomb raised questions about the ethics of conducting certain types of research in the physical sciences, recent work such as that mentioned here does the same for neuroscience. As it gains widespread interest and makes increasingly strong predictions about human beings and their behaviors, the power of great neuroscientific research must be wielded as gingerly as any.
1. Dalley, JW et al, (2007) Nucleus Accumbens D2/3 Receptors Predict Trait Impulsivity and Cocaine Reinforcement, Science, Vol. 315:1267-1270 | DOI: 10.1126/science.1137073
2. Klein, TA et al, (2007) Genetically Determined Differences in Learning from Errors, Science, Vol. 318:1642-1645 | DOI: 10.1126/science.1145044