First, I apologize for the tardiness of last week’s Neury Thursday, but I was too busy enjoying the long patriotic weekend doing this: Slip N Slide!!! It was like time travel back to 2nd grade before helicopter parents and neighborhood lawsuits.

Speaking of related tardiness, last week’s Journal of Neuroscience featured an article illustrating dopaminergic and amygdalar influences on impulsivity assessed through differences in the subjective value of sooner-smaller or later-larger monetary rewards between dopaminergically-medicated and unmedicated subjects. Using mathematical modeling, fMRI, dopamine agonists (L-dopa) and antagonists (haloperidol), and a complex, yet compelling experimental design, British neuroscientists revealed that highly upregulated dopaminergic states, induced through L-dopa,increased impulsivity and subsequently decreased amygdalar activity (I want that money now to buy an iPad and not six months from now when I will have more money and knowing that iPads will be 1/2 off because a newer generation will have been birthed by them, and therefore, I can buy two iPads!!!) . It’s almost as if attenuated activation of the amygdala concomitant with impulsivity serves as a protective mechanism against emotional irritability, preventing the opportunity to over-think and realize that the later-larger monetary reward was the better bargain. Very counterintuitive, indeed.

Here is a vibrant schematic (side note: I was disappointed to not see error bars on the graphs given the nuanced experimental design) and a few fMRI images from the paper. Descriptions of the graphs are viewable by dragging the mouse over the picture (which I hope that many of you have figured out by now!)

The broader implication of this research, aside from elucidating neural mechanisms of impulsivity which is a hallmark symptom of many psychiatric disorders, such as ADHD and schizophrenia, and L-dopa-treated Parkinsonian patients, is illustrating the adverse effects of dopamine on decision-making in addition to its pathological contributions to addiction, grandiose delusions, and motor discoordination of restless legs syndrome and Parkinson’s; drug addict researchers know that impulsivity is increasingly common in drug addicts–overlooking monetary, health, and environmental risks to obtain the drug of choice–and that the administration of dopamine pharmacological agents to patients with restless legs syndrome can cause them ResearchBlogging.orgto engage in addicting behaviors like gambling and online-shopping, drive, and even rape in their sleep (!!!; see previous post). This research, moreover, illustrates the need to reconsider the adverse side effects of many popular pharmacological treatments such as L-dopa, which does alleviate Parkinsonian tremors and generates huge payout for its shareholders, because it may be that dopamine, given the increasing diagnosis of Parkinson’s and subsequent filling of L-dopa prescriptions, has a greater contribution to the economic recession than previously believed….or even considered…….and certainly can facilitate a vicious spiral of economic malaise for the L-dopa-treated Parkinsonian patient.

Pine A, Shiner T, Seymour B, & Dolan RJ (2010). Dopamine, time, and impulsivity in humans. The Journal of neuroscience : the official journal of the Society for Neuroscience, 30 (26), 8888-96 PMID: 20592211