The Mesocortical Dopamine Projection to Anterior Cingulate Cortex Plays No Role in Guiding Effort-Related Decisions.

Both mesolimbic dopamine (DA) and the anterior cingulate cortex (ACC) have been implicated in enabling animals to expend effort to obtain greater reward. To investigate the role of the DA pathway to ACC in working for reward, the authors tested rats on a cost-benefit T-maze paradigm in which they could either climb a barrier to obtain large reward in 1 arm (high reward [HR]) or select the low-effort alternative containing less reward (low reward [LR]). Surprisingly, ACC DA depletions had no effect on choice performance. Manipulations of barrier and reward sizes demonstrated that lesioned rats were as sensitive to the costs and benefits of the alternatives as controls. These results imply that the DA projection to ACC is not involved in guiding effort-related decisions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Involvement of catecholamine neurotransmission in the rat anterior cingulate in effort-related decision making.

This study examined whether catecholamine-mediated signals in the anterior cingulate cortex (ACC) contribute to effort-based decision making. Rats were tested after 6-hydroxydopamine or vehicle infusions into the ACC in a T maze cost-benefit task in which the rats could choose either to climb a barrier to obtain a high reward in one arm or run into the other arm without a barrier to obtain a low reward. Results demonstrate that infusions of 6-hydroxydopamine induced a near total loss of tyrosine hydroxylase-positive fibers in the ACC. Unlike sham-lesioned rats, 6-hydroxydopamine-lesioned rats exhibited a reduced preference for the high-cost-high-reward response option when given the choice of obtaining a low reward with little effort. Thus, catecholamine-mediated signals in the ACC could play a role in effort-based decision making. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orbitofrontal cortex and basolateral amygdala lesions result in suboptimal and dissociable reward choices on cue-guided effort in rats.

The orbitofrontal cortex (OFC) and basolateral nucleus of the amygdala (BLA) are important neural regions in responding adaptively to changes in the incentive value of reward. Recent evidence suggests these structures may be differentially engaged in effort and cue-guided choice behavior. In 2 T-maze experiments, we examined the effects of bilateral lesions of either BLA or OFC on (1) effortful choices in which rats could climb a barrier for a high reward or select a low reward with no effort and (2) effortful choices when a visual cue signaled changes in reward magnitude. In both experiments, BLA rats displayed transient work aversion, choosing the effortless low reward option. OFC rats were work averse only in the no cue conditions, displaying a pattern of attenuated recovery from the cue conditions signaling reward unavailability in the effortful arm. Control measures rule out an inability to discriminate the cue in either lesion group. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Dopamine modulates effort-based decision making in rats.

Previous research has implicated dopamine as a modulating factor in choice behavior based on effort. The purpose of the present study was to determine the individual contribution of different dopamine receptors to effort-based decision making in rats. Rats were trained in a T-maze to choose a large-reward arm that contained 8 pellets of food over a small-reward arm that contained 2 pellets of food. The rats then were trained to climb progressively higher barriers to obtain the food from the large-reward arm. Using a discounting procedure on each test day, it was found that rats were more likely to choose the small-reward arm after treatment with the D1 antagonist, SCH-23390, or the D2 antagonist, haloperidol. The dopamine agonist, D-amphetamine, biased the rats toward choosing the large-reward arm and blunted the effects of SCH-23390 or haloperidol. Treatment with the D3 receptor antagonist, U99194, or the D3 receptor agonist, 7-OH-DPAT, did not alter choice behavior. These data indicate that D1 and D2 receptors are required for decisions based on effort. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A role for dorsal and ventral hippocampus in inter-temporal choice cost-benefit decision making.

Previous studies suggest a preferential role for dorsal hippocampus (dHPC) in spatial memory tasks, whereas ventral hippocampus (vHPC) has been implicated in aspects of fear and/or anxiety. In this study, we tested the hypothesis that vHPC may be a critical subregion for performance on a delay-based, cost-benefit decision making task. Rats chose between the two goal arms of a T maze, one containing an immediately available small reward, the other containing a larger reward that was only accessible after a delay. dHPC, vHPC, and complete hippocampal (cHPC) lesions all reduced choice of the delayed high reward (HR) in favor of the immediately available low reward (LR). The deficits were not due to a complete inability to remember which reward size was associated with which arm of the maze. When an equivalent 10-s delay was introduced in both goal arms, all rats chose the HR arm on nearly all trials. The deficit was, however, reinstated when the inequality was reintroduced. Our results suggest an important role for both dHPC and vHPC in the extended neural circuitry that underlies intertemporal choice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correlation between head direction cell activity and spatial behavior on a radial arm maze.

This study assessed the activity of head direction (HD) cells during performance of a spatial reference memory task on a radial arm maze. Rats were trained to select a maze arm located in a constant position in relation to a salient extramaze visual landmark. HD cell discharge properties remained relatively stable across task acquisition in most rats. Following acquisition, rotation of the landmark by 90° or 180° usually led to a corresponding shift in the maze arm selected and the HD cell's preferred firing direction. When the cell's preferred direction did not shift, rats usually selected the wrong arm. HD cell activity was not influenced by the rat's approach to the goal, reward consumption, or exit from the reward area. This demonstration of landmark control over behavior and the cell's preferred direction supports the hypothesis that HD cells contribute to an absolute representation of the environment that can be used to guide spatial behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nucleus accumbens dopamine depletions alter relative response allocation in a T-maze cost/benefit task

This experiment was conducted to study the role of nucleus accumbens dopamine in the performance of a novel T-maze cost/benefit procedure. Rats were trained on a T-maze task for food reinforcement. Under one of the test conditions, one arm of the maze contained a high reinforcement density (4 x 45 mg Bioserve pellets) and the other arm contained a low reinforcement density (2 x 45 mg pellets). A large vertical barrier (44 cm) was placed in the arm that contained the high density of food reinforcement. In the second test condition, a separate group of rats was trained in the same T-maze, in which there were 4 food pellets in the arm that was obstructed by the barrier, yet there were no food pellets in the unobstructed arm. After training rats received intra-accumbens of injections 6-hydroxydopamine or ascorbate vehicle. Nucleus accumbens dopamine depletions substantially decreased the number of selections of the obstructed arm with the high reinforcement density when the unobstructed arm also contained 2 food pellets. Dopamine-depleted rats in this condition showed increased selection of the no-barrier arm as well as decreased entry into the arm that contained the barrier. These effects persisted throughout the 3 weeks of post-surgical testing. Nevertheless, when the unobstructed arm contained no food pellets, and the only way to obtain food was to climb the barrier, rats with nucleus accumbens dopamine depletions showed only a modest effect on selections of the obstructed arm, which recovered by the second week of testing. Dopamine-depleted rats that were tested with food in the unobstructed arm showed significantly fewer barrier crossings than dopamine-depleted rats that were tested with no food in the unobstructed arm. Thus, the present findings are not consistent with the notion that nucleus accumbens dopamine depletion rendered the animals unable to climb the barrier, or set an absolute ceiling on the number of barrier crossings the animals could perform. Instead, the present results indicate that nucleus accumbens dopamine depletions affected the relative allocation of barrier climbing responses if alternative food sources were available.     

Dopamine Antagonists Do Not Block Conditioned Place Preference Induced by Paced Mating Behavior in Female Rats.

The authors assessed the behavioral effects of dopamine (DA) receptor antagonists, Cis (Z) flupentixol and S(+)-raclopride L-tartrate, on conditioned place preference (CPP) induced by paced mating behavior. Ovariectomized female rats of the Wistar strain were used. The administration of amphetamine (1 ior. mg/kg) induced a clear CPP that was completely blocked by the DA antagonists flupentixol (0.25 mg/kg) or raclopride (0.125 mg/kg). These doses had no effect on motor coordination. Female rats that mated in a pacing chamber developed a clear CPP. Neither flupentixol nor raclopride blocked the reward state induced by paced mating behavior. These results indicate that DA is not involved in the reward state induced by paced mating behavior in female rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Item and order information in spatial memory.

14 male Holtzman albino rats were taught to perform order and item discriminations in an 8-arm radial maze. In Exp I, 2 groups of Ss learned different order discriminations with reward contingent on repeating or avoiding the most recently visited of 2 locations. Each trial began with a random order of 8 forced choices and ended with a choice between the 1st and 7th arms. Rate of learning depended on the compatibility of reward contingencies and preexperimental response biases. In Exp II, each trial began with a list of 7 forced choices and ended in a choice between either the 1st or 6th arm and the arm not presented; accuracy of performing these item discriminations depended on both serial position and the response tendencies acquired in Exp I. In Exp III, a 1-hr postlist delay impaired the order discrimination more than the item discrimination, and the effects of intertrial interval depended on previously acquired response biases. Results are discussed in terms of a 2-stage model that segregates a single memory process from decision/response processes. Item and order discriminations do not appear to be based on separate sources of information and do not appear to require fundamentally different memory processes. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of Pavlovian and instrumental incentive learning under dopamine antagonists.

The administration of the dopamine antagonists, pimozide and α-flupenthixol, to rats reduced Pavlovian–instrumental transfer when a conditioned stimulus (CS) that had been paired with a noncontingent food reward was tested on instrumental performance. The administration of the antagonists during Pavlovian conditioning and/or testing abolished the enhancement of instrumental performance by the CS. The effect of both antagonists on instrumental incentive learning was then examined. After training in which the rats performed 2 responses for different food rewards, they consumed 1 type food under the antagonists and the other type under vehicle during reexposure. When instrumental responding was subsequently tested in extinction, performance was unaffected by whether the rats had been reexposed to the training reward under the antagonists. These results suggest that Pavlovian and instrumental incentive learning are not mediated by a common process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

D2 dopamine receptor antisense oligodeoxynucleotide inhibits the synthesis of a functional pool of D2 dopamine receptors

In vivo administration of an antisense oligonucleotide targeted toward the D2 dopamine (DA) receptor mRNA (D2 AS) markedly inhibited D2 receptor-mediated behaviors but produced only a relatively small reduction in the levels of D2 DA receptors in mouse striatum. This apparent dissociation between DA receptor-mediated behaviors and the levels of D2 DA receptors was addressed by inhibiting the total number of D2 DA receptors by intraperitoneal administration of the selective, irreversibly acting D2 DA receptor antagonist fluphenazine-N-mustard (FNM) and then determining the effects of D2 AS, administered intracerebroventricularly, on the rate of synthesis of D2 DA receptors and on the recovery of D2 receptor-mediated behaviors. FNM inactivated approximately 90% of D2 DA receptors within 4 hr of treatment, after which the receptors returned to normal levels by approximately 8 days. D2 AS treatment significantly inhibited the rate of recovery of D2 DA receptors in striatum of FNM-treated mice. FNM treatment also produced a number of behavioral alterations, including catalepsy, and the inhibition of stereotypic behavior induced by the D2/D3 DA receptor agonist quinpirole. Both of these behaviors returned to normal within 8 days after FNM treatment. D2 AS treatment delayed the restoration of these FNM-induced behaviors. Thus, it reduced the rate of disappearance of the cataleptic behavior induced by FNM and significantly delayed the restoration of the stereotypic behavior induced by quinpirole. The changes induced by D2 AS on D2 receptor-mediated behaviors were reversed on cessation of D2 AS treatment. A random oligomer given in the same amount and for the same length of time as that of the D2 AS had no significant effects on either D2 DA receptor synthesis or DA receptor-mediated behaviors. These studies demonstrate that in vivo administration of D2 AS decreased the rate of recovery of D2 DA receptors and inhibited the recovery of D2 DA receptor-mediated behaviors after irreversible receptor inactivation and suggest that D2 AS treatment inhibits the synthesis of a functional pool of D2 DA receptors.     

Retroactive interference effects of surprising reward omission on serial spatial memory.

Reward omission was used to produce retroactive interference in a serial delayed-alternation task. Rats were given forced choices in 3 T mazes presented in succession followed by free choices in which the alternate arm in each maze was rewarded. Nonreward during the delay between forced- and free-choice runs produced a decrement in performance (i.e., retroactive interference) in comparison to reward during the delay. Interference in retention of the first maze in a list occurred when the second maze contained surprising reward or omission (i.e., an outcome contrary to previous training in that maze) in comparison to expected reward or omission. In addition to producing retroactive interference, omission sometimes increased alternation in the maze in which it occurred. These results support a differential rehearsal hypothesis of spatial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The various perceptions of distance: An alternative view of how effort affects distance judgments.

D. R. Proffitt and colleagues (e. g., D. R. Proffitt, J. Stefanucci, T. Banton, & W. Epstein, 2003) have suggested that objects appear farther away if more effort is required to act upon them (e.g., by having to throw a ball). The authors attempted to replicate several findings supporting this view but found no effort-related effects in a variety of conditions differing in environment, type of effort, and intention to act. Although they did find an effect of effort on verbal reports when participants were instructed to take into account nonvisual (cognitive) factors, no effort-related effect was found under apparent- and objective-distance instruction types. The authors’ interpretation is that in the paradigms tested, effort manipulations are prone to influencing response calibration because they encourage participants to take nonperceptual connotations of distance into account while leaving perceived distance itself unaffected. This in no way rules out the possibility that effort influences perception in other contexts, but it does focus attention on the role of response calibration in any verbal distance estimation task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine receptor-mediated mechanisms involved in the expression of learned activity of primate striatal neurons

To understand the mechanisms by which basal ganglia neurons express acquired activities during and after behavioral learning, selective dopamine (DA) receptor antagonists were applied while recording the activity of striatal neurons in monkeys performing behavioral tasks. In experiment 1, a monkey was trained to associate a click sound with a drop of reward water. DA receptor antagonists were administered by micropressure using a stainless steel injection cannula (300 microm ID) through which a Teflon-coated tungsten wire for recording neuronal activity had been threaded. Responses to sound by tonically active neurons (TANs), a class of neurons in the primate striatum, were recorded through a tungsten wire electrode during the application of either D1- or D2-class DA receptor antagonists (total volume <1 microl, at a rate of 1 microl/5-10 min). Application of the D2-class antagonist, (-)-sulpiride (20 micrograms/microl, 58 mM, pH 6.8), abolished the responses of four of five TANs examined. In another five TANs, neither the D2-class antagonist nor the D1-class antagonists, SCH23390 (10 micrograms/microl, 31 mM, pH 5.7) or cis-flupenthixol (30 micrograms/microl, 59 mM, pH 6.6) significantly suppressed responses. In experiment 2, four- or five-barreled glass microelectrodes were inserted into the striatum. The central barrel was used for extracellular recording of activity of TANs. Each DA receptor antagonist was iontophoretically applied through one of the surrounding barrels. SCH23390 (10 mM, pH 4.5) and (-)-sulpiride (10 mM, pH 4.5) were used. The effects of iontophoresis of both D1- and D2-class antagonists were examined in 40 TANs. Of 40 TANs from which recordings were made, responses were suppressed exclusively by the D2-class antagonist in 19 TANs, exclusively by the D1-class antagonist in 3 TANs, and by both D1- and D2-class antagonists in 7 TANs. When 0.9% NaCl, saline, was applied by pressure (<1 microl) or by iontophoresis (<30 nA) as a control, neither the background discharge rates nor the responses of TANs were significantly influenced. Background discharge rate of TANs was also not affected by D1- or D2-class antagonists applied by either micropressure injection or iontophoresis. It was concluded that the nigrostriatal DA system enables TANs to express learned activity primarily through D2-class and partly through D1-class receptor-mediated mechanisms in the striatum.     

Does Octopus vulgaris have preferred arms?

Previous behavioral studies in Octopus vulgaris revealed lateralization of eye use. In this study, the authors expanded the scope to investigate arm preferences. The octopus's generalist hunting lifestyle and the structure of their arms suggest that these animals have no need to designate specific arms for specific tasks. However, octopuses also show behaviors, like exploration, in which only single or small groups of arms are involved. Here the authors show that octopuses had a strong preference for anterior arm use to reach for and explore objects, which points toward a task division between anterior and posterior arms. Four out of 8 subjects also showed a lateral bias. In addition, octopuses had a preference for a specific arm to reach into a T maze to retrieve a food reward. These findings give evidence for limb-specialization in an animal whose 8 arms were believed to be equipotential. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive strategy selection in decision making.

The role of effort and accuracy in the adaptive use of decision processes is examined. A computer simulation using the concept of elementary information processes identified heuristic choice strategies that approximate the accuracy of normative procedures while saving substantial effort. However, no single heuristic did well across all task and context conditions. Of particular interest was the finding that under time constraints, several heuristics were more accurate than a truncated normative procedure. Using a process-tracing technique that monitors information acquisition behaviors, two experiments tested how closely the efficient processing patterns for a given decision problem identified by the simulation correspond to the actual processing behavior exhibited by subjects. People appear highly adaptive in responding to changes in the structure of the available alternatives and to the presence of time pressure. In general, actual behavior corresponded to the general patterns of efficient processing identified by the simulation. Finally, learning of effort and accuracy trade-offs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine receptor blockade and extinction differentially affect behavioral variability.

Dopamine (DA) neurons respond to unexpected food delivery and are inhibited during the omission of expected reward. DA receptor blockade mimics some, but not all, aspects of nonreward (extinction) conditions. It was therefore of interest to ask whether DA receptor blockade produces extinction-like increases in behavioral variability in addition to its well-known operant response-suppressing effects. In the current experiment, rats were trained drug-free on an operant task in which they pressed on a keyboard. Two of the keys led to food on a continuous reinforcement schedule. Both response rates and behavioral variability were measured. Test day administration of D? and D? antagonists SCH23390 and raclopride, like extinction, suppressed responding but, unlike extinction, did not lead to an increase in variability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial analysis of the effects of methimazole therapy on circulating B cell subsets in Graves'' disease

Acetylcholine (ACh) systems have been widely shown to be important for memory. In particular, ACh hippocampal neurons are critical for memory formation, though ACh innervation of other areas such as the nucleus accumbens may also be important. There has also been increasing interest in ACh and dopaminergic (DA) interactions with regard to short-term spatial memory. In a series of studies, we have found that ACh and DA agonists and antagonists given systemically interact to influence memory. The critical neural loci of these interactions are not currently known. In the present study, we used local infusion techniques to examine the role of ACh and DA transmitter systems in the nucleus accumbens and the ventral hippocampus on radial-arm maze (RAM) working memory performance. Into the nucleus accumbens of rats, we infused the nicotinic ACh agonist nicotine, the nicotinic ACh antagonist mecamylamine, the DA agonist apomorphine, or the DA antagonist haloperidol. Into the ventral hippocampus, we infused nicotine, mecamylamine, the muscarinic ACh agonist pilocarpine, or the muscarinic ACh antagonist, scopolamine. The nicotinic ACh and DA interaction was tested by a hippocampal infusion of mecamylamine alone or together with the DA D2 agonist quinpirole given via subcutaneous injection. The results confirmed that both nicotinic and muscarinic ACh receptors in the ventral hippocampus play a significant role in spatial working memory. Blockade of either nicotinic or muscarinic ACh receptors caused significant impairments in RAM choice accuracy. However, infusion of either nicotinic or muscarinic agonists failed to improve choice accuracy. The interaction of DA D2 systems in different with hippocampal nicotinic blockade than with general nicotinic blockade. Systemic administration of quinpirole potentiated the amnestic effect of mecamylamine infused into the ventral hippocampus, whereas it was previously found to reverse the amnestic effect of systemically administered mecamylamine. In contrast to the significant effects of mecamylamine in the hippocampus, no effects were found after infusion into the nucleus accumbens. Nicotine also was not found to have a significant effect on memory after intra-accumbens infusion. Neither the DA agonist apomorphine nor the DA antagonist haloperidol had a significant effect on memory after infusion into the nucleus accumbens. This study provides support for the involvement of nicotinic and muscarinic receptors in the ventral hippocampus in memory function. Ventral hippocampal nicotinic systems have significant interactions with D2 systems, but these differ from their systemic interactions. In contrast, nicotinic ACh and DA systems in the nucleus accumbens were not found in the current study to be important for working memory performance in the RAM.     

Early social deprivation disrupts attentional, but not affective, shifts in rats.

This study examined the effects of early social deprivation in rats in 2 dissociable forms of inhibitory control of behavior that operate at 2 different levels of response selection: reversing the assignment of stimulus–reward associations within perceptual dimensions (affective shifts) and switching selective attention from 1 perceptual dimension to another (attentional shifts). Isolated Ss (isolates) and social controls (socials) were individually trained to spatial and nonspatial visual discrimination criteria on a radial arm maze. Whereas isolates and socials differed in neither acquisition nor reversal of both versions of the task, isolates were selectively impaired in shifting from spatial to nonspatial discrimination and vice versa. These findings demonstrate that isolation rearing selectively disrupts inhibitory control in attentional selection but leaves inhibitory control in affective processing intact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fixed-ratio schedules increase generalized self-control: Preference for large rewards despite high effort or punishment.

Three experiments investigated the effects of FR reinforcement on generalized self-control involving high effort and punishment. In Experiment 1, rats received food in a runway for the completion of each round trip (continuous-reinforcement group) or every fifth round trip (FR group). Control rats received food at the same temporal intervals as these groups but without any instrumental requirement. When all rats were next given a series of choices between a large food reward requiring high lever force versus a small reward requiring low lever force, the FR rats showed the greatest self-control. In Experiments 2 and 3, rats were rewarded on a continuous or FR schedule followed by choice between a large food reward accompanied by intermittent shock vs a small or absent food reward without shock. The FR rats again showed the greatest self-control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)