Motivational states influence effort-based decision making in rats: The role of dopamine in the nucleus accumbens

Abstract

Decision-making policies are subject to modulation by changing motivational states. However, so far, little is known about the neurochemical mechanisms that bridge motivational states with decision making. Here we examined whether dopamine (DA) in the nucleus accumbens core (AcbC) modulates the effects of motivational states on effort-based decision making. Using a cost-benefit T-maze task in rats, we examined the effects of AcbC DA depletions on effort-based decision making, in particular on the sensitivity of effort-based decision making to a shift from a hungry to a sated state. The results demonstrated that, relative to sham controls, rats with AcbC DA depletion in a hungry as well as in a sated state had a reduced preference for effortful but large-reward action. This finding provides further support for the notion that AcbC DA regulates how much effort to invest for rewards. Importantly, our results further revealed that effort-based decision making in lesioned rats, as in sham controls, was still sensitive to a shift from a hungry to a sated state; that is, their preferences for effortful large-reward actions became lower after a shift from a restricted to a freefeeding regimen. These finding indicate that AcbC DA is not necessarily involved in mediating the effects of a shift in motivational state on decision-making policies.

Orbitofrontal or accumbens dopamine depletion does not affect risk-based decision making in rats

“…These findings are consistent with previous data demonstrating that intra-AcbS infusions of the same or lower doses of 6-OHDA clearly reduced the striatal DA innervation assessed by an analysis of DA transporter density (Boye, Grant, & Clarke, 2001) and DA tissue content (Nelson, Thur, Horsley, Spicer, Marsden, & Cassaday 2011;Sokolowski & Salamone, 1998). Likewise, intraAcbC infusions of 6-OHDA at a lower dose markedly decreased TH-immunoreactivity (Lex & Hauber, 2010b;Mai, Sommer, & Hauber, 2012). It should be noted that in most lesioned rats, THimmunoreactivity was also reduced in an area restricted to the most medial part of adjacent AcbC (Fig.…”

Neurobiological basis of motivational deficits in psychopathology

“…The behavioral procedures used include a T-maze task that provides an effort-related challenge by having a vertical barrier in the arm with the higher reward value (Salamone et al, 1994;Cousins et al, 1996), operant tasks that give a choice between lever pressing for the more preferred reward (high carbohydrate pellets) vs. approaching and consuming a less preferred food (chow) that is concurrently available in the chamber (Salamone et al, 1991;Randall et al, 2012), and effort discounting tasks (Floresco et al, 2008;Bardgett et al, 2009). Regardless of the particular task used, the overall pattern of results is the same; interfering with DA transmission by local or intraaccumbens administration of DA antagonists, as well as NAcc DA depletions, shifts choice behavior by decreasing selection of the high effort option and increasing selection of the low effort option (Salamone et al, 1991(Salamone et al, , 1994(Salamone et al, , 2007Nowend et al, 2001;Floresco et al, 2008;Pardo et al 2012;Farrar et al, 2010;Randall et al, 2012;Mai et al, 2012). These effects are not due to changes in appetite, food preference, discrimination of reinforcement magnitude, or reference memory for the food location (Salamone et al, 1991;Salamone and Correa, 2002;Sink et al, 2008;Pardo et al, 2012), and the effects of DA antagonism on effort discounting are dissociable from effects on delay discounting (Floresco et al, 2008).…”

Activation of cannabinoid system in anterior cingulate cortex and orbitofrontal cortex modulates cost-benefit decision making

“…Among neurotransmitter systems, the involvement of dopamine (DA) system in effort-based decision making has been well established, particularly for the mesolimbic dopaminergic projection system that innervates the NAc (Hauber and Sommer 2009;Mai et al 2012;Salamone et al 1994). The involvement of the mesocortical dopaminergic pathway projecting to the ACC in decision making is less clear and remains a subject of debate.…”