Decision making: effects of methylphenidate on temporal discounting in nonhuman primates

Abstract

Decisions are often made based on which option will result in the largest reward. When given a choice between a smaller but immediate reward and a larger delayed reward, however, humans and animals often choose the smaller, an effect known as temporal discounting. Dopamine (DA) neurotransmission is central to reward processing and encodes delayed reward value. Impulsivity, the tendency to act without forethought, is associated with excessive discounting of rewards, which has been documented in patients with attention deficit hyperactivity disorder (ADHD). Both impulsivity and temporal discounting are linked to the dopaminergic system. Methylphenidate (MPH), which blocks the DA transporter and increases extracellular levels of DA in the basal ganglia and prefrontal cortex, is a primary treatment for ADHD and, at low doses, ameliorates impulsivity in both humans and animals. This study tested the hypothesis that low doses of MPH would decrease the discounting rate of rhesus monkeys performing an intertemporal choice task, suggesting a reduction in impulsivity. The results support this hypothesis and provide further evidence for the role of DA in temporal discounting and impulsive behavior.

Ventral striatum supports Methylphenidate therapeutic effects on impulsive choices expressed in temporal discounting task

“…Consistent with the literature [9][10][11][12][13][14] , therapeutic effects on impulsive choices were observed at the low dose. Notably, the MPH effect depended on the animals' initial impulsive state 49,50 .…”

Dopamine Modulation of Intertemporal Decision-making: Evidence from Parkinson Disease

“…Our results are consistent with findings in many pharmacological studies that increasing dopamine levels leads to more patient choices, whereas decreasing dopamine levels leads to decreases in choice of delayed rewards or willingness to exert effort for larger rewards (Kayser et al, 2012;Salamone & Correa, 2012;Floresco, Tse, & Ghods-Sharifi, 2008;Bizot et al, 2007;Salamone, Correa, Farrar, & Mingote, 2007;van Gaalen, van Koten, Schoffelmeer, & Vanderschuren, 2006;Pietras, Cherek, Lane, Tcheremissine, & Steinberg, 2003;de Wit, Enggasser, & Richards, 2002;Cardinal, Robbins, & Everitt, 2000;Wade, de Wit, & Richards, 2000;Richards, Sabol, & de Wit, 1999). In particular, a recent study showed that administration of methylphenidate, which increases extracellular levels of dopamine in the BG and pFC, decreased temporal discounting in nonhuman primates (Rajala, Jenison, & Populin, 2015). However, other studies have found that increases in dopamine lead to decreases in patient choices (Pine et al, 2010;Evenden & Ryan, 1996;Logue et al, 1992) or to no differences (Acheson & de Wit, 2008;Hamidovic, Kang, & de Wit, 2008).…”

Linking ADHD to the Neural Circuitry of Attention

“…One study [69] proposes that different sub-populations with ADHD exist, with distinguishable symptoms, cognitive and physiological profiles, which are caused by deficits in either the modulation of cortical control centers or reward circuits. Recent studies in nonhuman primates 1) identified the orbitofrontal cortex as a region that processes reward but not working memory-related information [70], 2) demonstrated reward signals integrate with action signals in at least one region of the prefrontal cortex (dorsal anterior cingulate cortex) [71] and 3) showed that administration of methylphenidate affected the temporal discounting of rewards [72]. …”