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At least 19 recordsLinked to original sources
PubMed2003

Reward value invariant place responses and reward site associated activity in hippocampal neurons of behaving rats.

To investigate the involvement of the hippocampal-accumbens system in goal-oriented displacement behaviors, hippocampal neuronal activity was recorded in rats learning and recalling new distributions of different volumes of liquid reward among the arms of a plus maze. Each arm had a reward box containing a water trough and identical visual cues that could be illuminated independently. As the water-restricted rat successively visited the respective boxes, it received 7, 5, and 3 drops of water, and then 1 drop, provided at 1-s intervals. (Reward distributions were reassigned daily and mid-session.) In the training phase, reward boxes were lit individually. In the recall phase, the lamps on all arms were lit and then turned off as the rat visited the boxes in order of descending value. Neuronal firing rates were analyzed for changes related to reward value or to shifts between learning and recall phases. The principal finding is that place responses remained unchanged after these manipulations and that these neurons showed no evidence of explicit coding of reward value. In addition, two other types of responses appeared while the rat was stationary at the reward boxes awaiting multiple rewards. These were observed primarily in neurons within the dentate gyrus, but also in CA1. Position-selective reward site responses were regular at 20-60 impulses per second, while position-independent discharges bursted irregularly at about 5 impulses per second. Such responses could explain controversial reports of reward dependence in hippocampal neurons. The higher incidence of the latter responses in the temporal ("ventral") hippocampus is consistent with the distinctive anatomical and functional properties of this subregion.

Action Potentials↗
PubMed1999

Psychopharmacology of conditioned reward: evidence for a rewarding signal at D1-like dopamine receptors.

A neutral stimulus can acquire conditioned rewarding properties through association with an intrinsically rewarding stimulus. The acquisition of responding for conditioned rewards requires that environmental stimuli and reward processes interact in a highly specific manner; analyses of this phenomenon may provide valuable insight into the processes that underlie reward-related learning. The effects of dopaminergic agents with different mechanisms of action in this paradigm have revealed several interesting dissociations suggesting that a rewarding signal at dopamine D1-like receptors may mediate both the acquisition of rewarding properties by neutral stimuli and their ability to control behavior. Dopamine-induced changes in responding for conditioned reward are susceptible to modulation by other neurotransmitter systems. In many cases, the molecular and cellular bases of these interactions support the notion that signaling through D1-like receptors is critical for a conditioned reward to direct responding. The model outlined in this paper reflects a comprehensive integration of the existing literature in the field, and has several implications that are readily testable by future research. Moreover, given the known biochemical coupling of D1-like receptors, this model may help in characterizing the sequence of intracellular events, from signal transduction to possible transcriptional and/or translational regulation, that give rise to the acquisition of rewarding properties by neutral stimuli.

Animals↗
PubMed1989

Electrical stimulation of the medial prefrontal cortex supports both 'pure reward' and 'reward-escape' behavior in rats.

In female Sprague-Dawley rats, 8 of 12 medial prefrontal cortex (MPFC) sites that yielded criterion self-stimulation behavior supported only self-stimulation, i.e. were 'pure reward' in type. The remaining 4 sites supported behavior to escape from experimenter-administered stimulation of the same parameters as well, i.e. were 'reward-escape' in type. 'Pure reward' and 'reward-escape' sites in the MPFC were distinguished by both the magnitude and temporal form of the escape response functions generated, and by the prevalence of 'pounce-back', a vigorous and repetitive barpressing during the 3-s MPFC stimulation-escape interval produced by an effective barpress. The finding that both 'pure reward' and 'reward-escape' patterns of behavior can be elicited by stimulation of the MPFC provides a basis for further assessment of similarities and differences in medial prefrontal cortical and lateral hypothalamic (LH) 'reward' systems. It is suggested that 'reward-escape' in the MPFC may be mediated by the activity of 'reward' neurons which respond to stimulus offset, rather than by a secondary aversive process as is proposed to underlie 'reward-escape' in the LH.

Animals↗
PubMed1998

What is the role of dopamine in reward: hedonic impact, reward learning, or incentive salience?

What roles do mesolimbic and neostriatal dopamine systems play in reward? Do they mediate the hedonic impact of rewarding stimuli? Do they mediate hedonic reward learning and associative prediction? Our review of the literature, together with results of a new study of residual reward capacity after dopamine depletion, indicates the answer to both questions is 'no'. Rather, dopamine systems may mediate the incentive salience of rewards, modulating their motivational value in a manner separable from hedonia and reward learning. In a study of the consequences of dopamine loss, rats were depleted of dopamine in the nucleus accumbens and neostriatum by up to 99% using 6-hydroxydopamine. In a series of experiments, we applied the 'taste reactivity' measure of affective reactions (gapes, etc.) to assess the capacity of dopamine-depleted rats for: 1) normal affect (hedonic and aversive reactions), 2) modulation of hedonic affect by associative learning (taste aversion conditioning), and 3) hedonic enhancement of affect by non-dopaminergic pharmacological manipulation of palatability (benzodiazepine administration). We found normal hedonic reaction patterns to sucrose vs. quinine, normal learning of new hedonic stimulus values (a change in palatability based on predictive relations), and normal pharmacological hedonic enhancement of palatability. We discuss these results in the context of hypotheses and data concerning the role of dopamine in reward. We review neurochemical, electrophysiological, and other behavioral evidence. We conclude that dopamine systems are not needed either to mediate the hedonic pleasure of reinforcers or to mediate predictive associations involved in hedonic reward learning. We conclude instead that dopamine may be more important to incentive salience attributions to the neural representations of reward-related stimuli. Incentive salience, we suggest, is a distinct component of motivation and reward. In other words, dopamine systems are necessary for 'wanting' incentives, but not for 'liking' them or for learning new 'likes' and 'dislikes'.

Animals↗
PubMed2003

Anticipation of reward in a nonaversive differential conditioning paradigm and the brain reward system: an event-related fMRI study.

Findings from animal as well as human neuroimaging studies suggest that reward delivery is associated with the activation of subcortical limbic and prefrontal brain regions, including the thalamus, the striatum, the anterior cingulate and the prefrontal cortex. The aim of the present study was to explore if these reward-sensitive regions are also activated during the anticipation of reinforcers that vary with regard to their motivational value. A differential conditioning paradigm was performed, with the presentation of a rewarded reaction time task serving as the unconditioned stimulus (US). Depending on their reaction time, subjects were given (or not given) a monetary reward, or were presented with a verbal feedback consisting of being fast or slow. In a third control condition no task needed to be executed. Each of the three conditions was introduced by a different visual cue (CS). Brain activation of 27 subjects was recorded using event-related functional magnetic resonance imaging. The results showed significant activation of the substantia nigra, thalamic, striatal, and orbitofrontal brain regions as well as of the insula and the anterior cingulate during the presentation of a CS signalling a rewarded task. The anticipation of a monetary reward produced stronger activation in these regions than the anticipation of positive verbal feedback. The results are interpreted as reflecting the motivation-dependent reactivity of the brain reward system with highly motivating stimuli (monetary reward) leading to a stronger activation than those less motivating ones (verbal reward).

Adult↗
PubMed1989

Preference for unpredictable food rewards occurs with high proportion of reinforced trials or alcohol if rewards are not delayed.

Organisms typically prefer situations where reward and nonreward are predictable rather than unpredictable. Although many theories can account for this result (e.g., information theory and delay-reduction theory), a recently developed mathematical model (DMOD) also predicts that subjects prefer the unpredictable reward situation under conditions that substantially decrease aversiveness of unpredictable nonreward (Daly & Daly, 1982). Because a high proportion of reinforced trials (lenient schedule) and alcohol injections decrease aversive conditioning, these variables were tested with rats in five E-maze experiments. A choice to one side of the maze resulted in a stimulus uncorrelated with reward outcome (unpredictable situation). A choice to the other side resulted in stimuli correlated with reward and nonreward (predictable situation). The stimuli were not visible until after the choice was made. A lenient reinforcement schedule resulted in preference for the unpredictable reward situation if rewards were not delayed. Alcohol resulted in preference for the unpredictable reward situation if a medium five-pellet reward was given. A lenient reinforcement schedule combined with an alcohol injection resulted in faster acquisition of the preference for the unpredictable reward situation than did a lenient schedule combined with a saline control injection. These results pose a major challenge to most theories, yet were predicted by DMOD.

Animals↗
PubMed2000

Lesions of the medial shell of the nucleus accumbens impair rats in finding larger rewards, but spare reward-seeking behavior.

The goal of this study was to help better understand the importance of the nucleus accumbens (Nacc) in the processing of position and reward value information for goal-directed orientation behaviors. Sixteen male Long-Evans rats, under partial water deprivation, were trained in a plus-maze to find water rewards in the respective arms which were lit in pseudo-random sequence (training trials). Each day one reward arm was selected to deliver six drops of water (at 1 s intervals) the others provided only one drop per visit. After 32 visits, probe trials were intermittently presented among training trials. Here, all four arms were lit and offered the previously assigned reward. The rats rapidly learned to go to the highly rewarded arm. Six trained rats were given bilateral electrolytic lesions in the Nacc shell, two others had unilateral lesions and eight had sham operations (with approved protocols). Field potentials evoked by fornix stimulation were recorded in lesion electrodes to guide placements. Only the lesioned rats showed significant impairments (P<0.05) in selecting the greater reward on probe trials. However on training trials, lesioned (and sham-operated) rats made only rare errors. While the motivation to drink and the capacity for cue-guided goal-directed orientation behavior was spared, lesioned rats were impaired in learning the location of the larger reward. The accumbens lesions apparently impaired integration of position and reward value information, consistent with anatomical and electrophysiological data showing the convergence of hippocampal, amygdalar, ventral tegmental area (VTA) and prefrontal cortical inputs there.

Amygdala↗
PubMed1998

Self-stimulating rats combine subjective reward magnitude and subjective reward rate multiplicatively.

For rats that bar pressed for intracranial electrical stimulation in a 2-lever matching paradigm with concurrent variable interval schedules of reward, the authors found that the time allocation ratio is based on a multiplicative combination of the ratio of subjective reward magnitudes and the ratio of the rates of reward. Multiplicative combining was observed in a range covering approximately 2 orders of magnitude in the ratio of the rates of reward from about 1:10 to 10:1) and an order of magnitude change in the size of rewards. After determining the relation between the pulse frequency of stimulation and subjective reward magnitude, the authors were able to predict from knowledge of the subjective magnitudes of the rewards and the obtained relative rates of reward the subject's time allocation ratio over a range in which it varied by more than 3 orders of magnitude.

Action Potentials↗
PubMed1977

Reward versus performance in self-stimulation: electrode-specific effects of alpha-methyl-p-tyrosine on reward in the rat.

The hypothesis that alpha-methyl-p-tyrosine (AMPT), an inhibitor of catecholamine synthesis, reduces brain stimulation reward was tested, using a measure of reward previously shown to be relatively unaffected by variables that alter performance but not reward. The rewarding effectiveness of stimulation was determined by the location of the sharp rise in the function relating running speed in an alley to the number of pulses received as a reward. For some electrodes, AMPT depressed self-stimulation performance (speed of running) without producing any sizable effect on the measure of reward (location of rise). For other electrodes, the rewarding effectiveness of the stimulation was greatly reduced by AMPT and restored by L-dopa. These opposing results could be repeatedly demonstrated on different electrodes in the same rat. The electrode-specific differential sensitivity to AMPT suggests neurochemically disparate substrates for reward.

Animals↗
PubMed2000

Effects of reward anticipation, reward presentation, and spatial parameters on the firing of single neurons recorded in the subiculum and nucleus accumbens of freely moving rats.

The subiculum is the major output of the hippocampal formation (involved in spatial processing). Subicular afferents innervate the nucleus accumbens, which is thought to integrate limbic reward information with motor output. Rats were chronically implanted with extra-cellular recording electrodes aimed at both structures to investigate the functional relationship between them. Animals were then trained on a spatial task in which they searched for random locations where they would receive rewarding medial forebrain bundle stimulation. At random times a cue tone was sounded, indicating that the reward location was in the center of the environment. Rats quickly learned to run to the center upon hearing the tone in order to receive a reward. Simultaneously recorded groups of up to eight subicular and accumbens neurons were found to display alterations in firing rate after rewarding medial forebrain bundle stimulation. Moreover, neurons in both subiculum and accumbens displayed alterations in firing rate prior to arrival at the center during cued runs, i.e. they anticipated predictable rewards. Subicular and accumbens firing was also correlated with spatial location. However, neurons in accumbens were more likely to respond to task events, and these responses were more varied, than those seen in subiculum. Thus, while convergence of spatial and reward information occurs at the level of single cells in both subiculum and nucleus accumbens, these structures also display functional localization.

Acoustic Stimulation↗
PubMed2000

Reward-predicting and reward-detecting neuronal activity in the primate supplementary eye field.

In addition to cells specifically active with visual stimuli, saccades, or fixation, the supplementary eye field contains cells that fire in precise temporal relationship with the occurrence of reward. We studied reward-related activity in two monkeys performing a prosaccade/antisaccade task and in one monkey trained in memory prosaccades only. Two types of neurons were distinguished by their reciprocal firing pattern: reward-predicting (RP) and reward-detecting (RD). RP neurons linearly increased their firing as early as 150 ms before saccade onset until the occurrence of reward, at which time they abruptly ceased firing. In contrast, RD neurons fired in phase with reward delivery, even when its duration was varied and when it was repeated at different frequencies. RD discharges were little affected or unaffected by the position of a visual cue that briefly anchored the goal at the onset of reward. The complementary firing patterns of the RP and RD neurons could provide a feedback mechanism necessary for learning and performing the task.

Animals↗
PubMed1989

Effects of reward and familiarity of reward agent on spontaneous play in preschoolers: a field study.

A field experiment was conducted with preschool children to test the effect of rewards on a familiar, spontaneous play activity, in conditions as close as possible to the children's natural school context, and to examine the role of familiarity of the person who administered rewards. In three experimental conditions, children were rewarded either by their own teacher or by an unknown adult for playing with toys at the school playground and stayed with either the teacher or the unknown adult in the remaining part of reward sessions. Spontaneous play was significantly reduced by the reward relative to baseline levels and recovered after a 3-wk. interval. However, no difference due to familiarity/unfamiliarity of reward agent could be found. Results, discussed in terms of an incentive contrast hypothesis, attest to the generality and external validity of the undermining effects of rewards.

Child, Preschool↗
PubMed1997

[Expectation of others' reward allocation, and ingroup favoritism in reward allocation].

The purpose of this study was to investigate people's expectation of others' ingroup favoritism, and the effect of expecting others to take part in reward allocation decision on ingroup favoritism in reward allocation. Subjects were randomly assigned to two groups, and were asked to rate attractiveness of ingroup members, and to allocate reward to ingroup and outgroup under two conditions. In the unilateral condition, the subject alone was to make the decision, and in the multilateral condition, every subject was to. The results indicated that equally in all conditions, subjects rated ingroup members more attractive, and expected others to allocate more reward to own groups. Reward allocation that favored ingroup occurred only under the multilateral condition, where everyone participated in reward allocation, regardless of whether the subject's own reward was dependent on others' decisions or was a fixed amount. The findings suggest that ingroup favoritism was not a result of quasi-strategy of self-interest in an attempt to maximize own gains, but of psychological group formation.

Adult↗
PubMed2025

Multi-Locus Pro-Dopaminergic Restoration of Reward Brain Circuitry in Reward Deficiency Rescinds Mono-Pharmaceutical Targeting.

Dopaminergic dysfunction in reward circuitry is well-documented as a contributor to addictive behaviors. Evidence indicates that changes in synchronous neural activity between brain regions mediating reward and cognitive functions may significantly contribute to substance-related disorders. In this commentary we highlight findings showing that the pro-dopaminergic nutraceutical (KB220) enhances functional connectivity between reward and cognitive brain areas in both animal and human studies. Animal studies demonstrate that KB220 activates important brain reward-related regions, including the nucleus accumbens, anterior cingulate gyrus, anterior thalamic nuclei, hippocampus, and prelimbic and infralimbic loci. Kb220 induced significant functional connectivity, enhanced neuroplasticity, and improved dopaminergic functionality within the brain reward circuitry with effects localized to these regions rather than broader distributed across the brain. In abstinent heroin-dependent individuals, acute KB220 administration significantly induced BOLD activation in caudate-accumbens dopaminergic pathways relative to placebo. Furthermore, data from 36 clinical trials and preclinical studies encompassing over 1,000 subjects, demonstrate that KB220 supports "dopamine homeostasis" across various reward deficiency behaviors. Clinical outcomes and quantitative electroencephalogy (qEEG) results underscore KB220's potential anti-craving/anti-relapse effects in addiction and other psychiatric disorders through direct or indirect dopaminergic modulation. Based on a review of the existing knowledge and further intensive investigation, we propose that instead of relying on mono-pharmaceutical approaches, the scientific community should endorse multi-loci dopaminergic restoration of reward brain circuitry as a fundamental paradigm for addressing mental illness.

Alcohol Use Disorder (AUD)↗
PubMed1983

Reward and aversive effects of lateral hypothalamic stimulation in rats measured by a modified runway and reward summation technique.

This report presents a refinement of the reward summation technique which has seen increasing use as a measure of the reward and performance factors associated with studies of the anatomical and neurochemical mechanisms of lateral hypothalamic stimulation. The technique involves determining the vigor of reward seeking behavior at a number of stimulation levels and making calculations upon this behavior/stimulation relationship. The refinement involves separating out the behavioral consequences of aversiveness which is often mixed with hypothalamic reward, particularly at high levels of stimulation. Specifically, it is shown that total running speed, the conventional measure of reward seeking behavior in a runway, is made of two components: running the runway and latency to press the reward lever. Furthermore, the latency-to-press the lever for any brain stimulation is positively correlated with latency to escape the same stimulation in an ON-OFF apparatus. Thus, latency-to-press likely is attributable to the aversiveness of the stimulation. Measuring only the first component is a more refined measure of the reward of brain stimulation.

Animals↗
PubMed1991

Measuring the subjective magnitude of brain stimulation reward by titration with rate of reward.

The magnitude of experienced reward as a function of the pulse frequency and current in trains of fixed duration delivered to the medial forebrain bundle of the rat was measured using a new psychophysical method in which the parameters of the brain stimulation reward on one lever are adjusted to offset the effect of changing the rate of reward on a competing lever. Subjective reward magnitude is a steep sigmoidal function of both pulse frequency and current. The growth of reward to its half-maximal level was approximated by a power function with an exponent that varied from 2 to 10. Within a subject, the exponent was the same for both current and pulse frequency, which supports the hypothesis that the magnitude of reward from a train of fixed duration is determined by the rate at which action potentials are generated in the population of reward-relevant axons (the counter hypothesis). This rate is proportional to Current x Pulse Frequency.

Animals↗