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PubMed2005

Neural coding of distinct statistical properties of reward information in humans.

Brain processing of reward information is essential for complex functions such as learning and motivation. Recent primate electrophysiological studies using concepts from information, economic and learning theories indicate that the midbrain may code two statistical parameters of reward information: a transient reward error prediction signal that varies linearly with reward probability and a sustained signal that varies highly non-linearly with reward probability and that is highest with maximal reward uncertainty (reward probability = 0.5). Here, using event-related functional magnetic resonance imaging, we disentangled these two signals in humans using a novel paradigm that systematically varied monetary reward probability, magnitude and expected reward value. The midbrain was activated both transiently with the error prediction signal and in a sustained fashion with reward uncertainty. Moreover, distinct activity dynamics were observed in post-synaptic midbrain projection sites: the prefrontal cortex responded to the transient error prediction signal while the ventral striatum covaried with the sustained reward uncertainty signal. These data suggest that the prefrontal cortex may generate the reward prediction while the ventral striatum may be involved in motivational processes that are useful when an organism needs to obtain more information about its environment. Our results indicate that distinct functional brain networks code different aspects of the statistical properties of reward information in humans.

Adult↗

PubMed2002

Influence of reward expectation on visuospatial processing in macaque lateral prefrontal cortex.

The lateral prefrontal cortex (LPFC) has been implicated in visuospatial processing, especially when it is required to hold spatial information during a delay period. It has also been reported that the LPFC receives information about expected reward outcome. However, the interaction between visuospatial processing and reward processing is still unclear because the two types of processing could not be dissociated in conventional delayed response tasks. To examine this, we used a memory-guided saccade task with an asymmetric reward schedule and recorded 228 LPFC neurons. The position of the target cue indicated the spatial location for the following saccade and the color of the target cue indicated the reward outcome for a correct saccade. Activity of LPFC was classified into three main types: S-type activity carried only spatial signals, R-type activity carried only reward signals, and SR-type activity carried both. Therefore only SR-type cells were potentially involved in both visuospatial processing and reward processing. SR-type activity was enhanced (SR+) or depressed (SR-) by the reward expectation. The spatial discriminability as expressed by the transmitted information was improved by reward expectation in SR+ type. In contrast, when reward information was coded by an increase of activity in the reward-absent condition (SR- type), it did not improve the spatial representation. This activity appeared to be involved in gaze fixation. These results extend previous findings suggesting that the LPFC exerts dual influences based on predicted reward outcome: improvement of memory-guided saccades (when reward is expected) and suppression of inappropriate behavior (when reward is not expected).

Animals↗

PubMed2005

Reward-spatial view representations and learning in the primate hippocampus.

The primate anterior hippocampus (which corresponds to the rodent ventral hippocampus) receives inputs from brain regions involved in reward processing, such as the amygdala and orbitofrontal cortex. To investigate how this affective input may be incorporated into primate hippocampal function, we recorded neuronal activity while rhesus macaques performed a reward-place association task in which each spatial scene shown on a video monitor had one location that, if touched, yielded a preferred fruit juice reward and a second location that yielded a less-preferred juice reward. Each scene had different locations for the different rewards. Of 312 neurons analyzed in the hippocampus, 18% responded more to the location of the preferred reward in different scenes, and 5% responded to the location of the less-preferred reward. When the locations of the preferred rewards in the scenes were reversed, 60% of 44 hippocampal neurons tested reversed the location to which they responded, showing that the reward-place associations could be altered by new learning in a few trials. The majority (82%) of these 44 hippocampal neurons tested did not respond to reward associations in a visual discrimination, object-reward association task. Thus, the primate hippocampus contains a representation of the reward associations of places "out there" being viewed. By associating places with the rewards available, the concept that the primate hippocampus is involved in object-place event memory is now extended to remembering goals available at different spatial locations. This is an important type of association memory.

Animals↗

PubMed1999

Operant ethanol reward in C57BL/6 mice: influence of gender and procedural variables.

Food-deprived C57BL/6 (C57) mice of either sex responded for oral ethanol rewards delivered on ratio schedules of reinforcement, thus extending to female C57 mice effects previously reported only for male members of the strain. Lever responding for ethanol reward was influenced by thirst motivation (post- vs. preprandial tests), time of access to ethanol reward, ethanol concentration, and reinforcement schedule. A particularly high response output for 12% ethanol delivered on a PR2 schedule (e.g., approximately 1400/15 min test session) indicates its efficacy as a reinforcer for C57 mice. Estimated consumption of ethanol differed from lever responding when reward access time was relatively long (10 s) and response demand of the reinforcement schedule was low, but paralleled lever responding when reward access time was restricted (3 s) and response demands were greater. Gender influenced lever responding for ethanol reward and its consumption, the difference depending upon reward access time and reinforcement schedule. When the response demands were low and the reward access time long, females tended to respond more than males for ethanol reward; with greater response demands and shorter reward access time, males tended to respond more. In conjunction with our companion report, the present study helps define the behavioral conditions under which ethanol is rewarding for C57 mice and establish the conditions under which ethanol reward differs for male and female mice.

Animals↗

PubMed2004

Synaptic and spiking dynamics underlying reward reversal in the orbitofrontal cortex.

Cognitive and emotional flexibility involve a coordinated interaction between working memory, attention, reward expectations, and the evaluation of rewards and punishers so that behaviour can be changed if necessary. We describe a model at the integrate-and-fire neuronal level of the synaptic and spiking mechanisms which can hold an expectation of a reward rule in working memory, and can reverse the reward rule if expected rewards are not obtained. An example of a reward rule is that stimulus 1 is currently associated with reward, and stimulus 2 with punishment. The attractor-based reward rule working memory incorporates a spike-frequency synaptic adaptation mechanism which supports the neural switching between rules by being shut down by a general inhibitory input produced by punishment, so that when the attractor starts up again is in the opposite state. The mechanism can implement one-trial reward reversal, which is a property of orbitofrontal cortex neurons. We show how this reward rule input can operate in a biased competition way to influence which one of two stimuli is currently associated with reward and which with punishment, and to map the stimuli correctly to the reward or punishment representations, providing a basis for action selection required to obtain the reinforcer.

Action Potentials↗

PubMed2004

Reward sensitivity in impulsivity.

Impulsive individuals choose immediate small over delayed larger rewards, suggesting reward hypersensitivity. Single-unit studies have shown increased ventral tegmental activity to rewards and reward predictors and decreased activity when predicted rewards are withheld. The orbitofrontal ventral tegmental cortical target also responds to reward and expectation in single-unit and neuroimaging studies. The anterior P2a event-related potential component is a proposed index of reward-related orbitofrontal activity. In this reward prediction study in high and low impulsive subjects, the P2a localized to orbitofrontal cortex and was largest to non-predicted rewards and smallest in the absence of predicted rewards in subjects higher on self-reported impulsiveness, consistent with a P2a index of orbitofrontal reward processing and with reward hypersensitivity in impulsivity.

Adolescent↗

PubMedDate not supplied

Involvement of the rat anterior cingulate cortex in control of instrumental responses guided by reward expectancy.

The anterior cingulate cortex (ACC) plays a critical role in stimulus-reinforcement learning and reward-guided selection of actions. Here we conducted a series of experiments to further elucidate the role of the ACC in instrumental behavior involving effort-based decision-making and instrumental learning guided by reward-predictive stimuli. In Experiment 1, rats were trained on a cost-benefit T-maze task in which they could either choose to climb a barrier to obtain a high reward (four pellets) in one arm or a low reward (two pellets) in the other with no barrier present. In line with previous studies, our data reveal that rats with quinolinic acid lesions of the ACC selected the response involving less work and smaller reward. Experiment 2 demonstrates that breaking points of instrumental performance under a progressive ratio schedule were similar in sham-lesioned and ACC-lesioned rats. Thus, lesions of the ACC did not interfere with the effort a rat is willing to expend to obtain a specific reward in this test. In a subsequent task, we examined effort-based decision-making in a lever-press task where rats had the choice between pressing a lever to receive preferred food pellets under a progressive ratio schedule, or free feeding on a less preferred food, i.e. lab chow. Results show that sham- and ACC-lesioned animals had similar breaking points and ingested comparable amounts of less-preferred food. Together, the results of Experiment 1 and 2 suggest that the ACC plays a role in evaluating how much effort to expend for reward; however, the ACC is not necessary in all situations requiring an assessment of costs and benefits. In Experiment 3 we investigated learning and reversal learning of instrumental responses guided by reward predictive stimuli. A reaction time (RT) task demanding conditioned lever release was used in which the upcoming reward magnitude (five vs. one food pellet) was signalled in advance by discriminative visual stimuli. Results revealed that rats with ACC lesions were able to discriminate reward magnitude-predictive stimuli and to adapt instrumental behavior to reversed stimulus-reward magnitude contingencies. Thus, in a simple discrimination task as used here, the ACC appears not to be required to discriminate reward magnitude-predictive stimuli and to use the learned significance of the stimuli to guide instrumental behavior.

Animals↗

PubMed2006

Reward-related decision-making in pediatric major depressive disorder: an fMRI study.

BACKGROUND: Although reward processing is considered an important part of affective functioning, few studies have investigated reward-related decisions or responses in young people with affective disorders. Depression is postulated to involve decreased activity in reward-related affective systems. METHODS: Using functional magnetic resonance imaging (fMRI), we examined behavioral and neural responses to reward in young people with depressive disorders using a reward decision-making task. The task involved choices about possible rewards involving varying magnitude and probability of reward. The study design allowed the separation of decision/anticipation and outcome phases of reward processing. Participants were 9-17 years old and had diagnoses of major depressive disorder (MDD), anxiety disorders, or no history of psychiatric disorder. RESULTS: Participants with MDD exhibited less neural response than control participants in reward-related brain areas during both phases of the task. Group differences did not appear to be a function of anxiety. Depressive and anxiety symptoms were associated with activation in reward-related brain areas. CONCLUSIONS: Results suggest that depression involves altered reward processing and underscore the need for further investigation of relations among development, affective disorders, and reward processing.

Adolescent↗

PubMed2000

Reward-related neuronal activity during go-nogo task performance in primate orbitofrontal cortex.

The orbitofrontal cortex appears to be involved in the control of voluntary, goal-directed behavior by motivational outcomes. This study investigated how orbitofrontal neurons process information about rewards in a task that depends on intact orbitofrontal functions. In a delayed go-nogo task, animals executed or withheld a reaching movement and obtained liquid or a conditioned sound as reinforcement. An initial instruction picture indicated the behavioral reaction to be performed (movement vs. nonmovement) and the reinforcer to be obtained (liquid vs. sound) after a subsequent trigger stimulus. We found task-related activations in 188 of 505 neurons in rostral orbitofrontal area 13, entire area 11, and lateral area 14. The principal task-related activations consisted of responses to instructions, activations preceding reinforcers, or responses to reinforcers. Most activations reflected the reinforcing event rather than other task components. Instruction responses occurred either in liquid- or sound-reinforced trials but rarely distinguished between movement and nonmovement reactions. These instruction responses reflected the predicted motivational outcome rather than the behavioral reaction necessary for obtaining that outcome. Activations preceding the reinforcer began slowly and terminated immediately after the reinforcer, even when the reinforcer occurred earlier or later than usually. These activations preceded usually the liquid reward but rarely the conditioned auditory reinforcer. The activations also preceded expected drops of liquid delivered outside the task, suggesting a primary appetitive rather than a task-reinforcing relationship that apparently was related to the expectation of reward. Responses after the reinforcer occurred in liquid- but rarely in sound-reinforced trials. Reward-preceding activations and reward responses were unrelated temporally to licking movements. Several neurons showed reward responses outside the task but instruction responses during the task, indicating a response transfer from primary reward to the reward-predicting instruction, possibly reflecting the temporal unpredictability of reward. In conclusion, orbitofrontal neurons report stimuli associated with reinforcers are concerned with the expectation of reward and detect reward delivery at trial end. These activities may contribute to the processing of reward information for the motivational control of goal-directed behavior.

Animals↗

PubMed2002

Role of primate substantia nigra pars reticulata in reward-oriented saccadic eye movement.

To test the hypothesis that the basal ganglia are related to reward-oriented saccades, we examined activity of substantia nigra pars reticulata (SNr) neurons by using a one-direction-rewarded version of the memory-guided saccade task (1DR). Many SNr neurons changed (decreased or increased) their activity after and before a visual cue (post-cue and pre-cue activity). Post-cue decreases or increases tended to be larger to a contralateral cue. They were often modulated prospectively by the presence or absence of reward, either positively (enhanced in the rewarded condition) or negatively (enhanced in the nonrewarded condition). The positive reward modulation was more common among decreasing type neurons, whereas no such preference was observed among increasing type neurons. The reward-contingent decrease in SNr neuronal activity would facilitate rewarded saccades by inducing disinhibition in superior colliculus (SC) neurons. In contrast, the increase in SNr activity would suppress a saccade less selectively (rewarded or nonrewarded) by augmenting inhibition of SC neurons. The post-cue activity was often preceded by anticipatory pre-cue activity. Most typically, post-cue decrease was preceded by pre-cue decrease, selectively when the contralateral side was rewarded. This would reinforce the reward-oriented nature of SNr neuronal activity. The decreases and increases in SNr activity may be derived directly and indirectly, respectively, from the caudate (CD), where neurons show reward-contingent pre-cue and post-cue activity. These results suggest that the CD-SNr-SC mechanism would promote saccades oriented to reward.

Animals↗

PubMed1994

Importance of unpredictability for reward responses in primate dopamine neurons.

1. We used single neuron recording techniques in two behaving monkeys to investigate the conditions in which dopamine neurons respond to primary rewarding or potentially rewarding stimuli. Animals received drops of liquid either outside behavioral tasks or as rewards during learning or established performance of an auditory reaction time task. 2. Three quarters of dopamine neurons showed a short-latency, phasic response to liquid that was delivered outside the task without being predicted by phasic stimuli. The same neurons responded to liquid reward during learning but not when task performance was established, at which time the neuronal response occurred to the conditioned, reward-predicting, movement-triggering stimulus. 3. These data suggest that the responses of dopamine neurons to rewarding or potentially rewarding liquid are due to the temporally unpredicted stimulus occurrence. A known, reward-predicting, tonic context does not prevent dopamine neurons from responding to the rewarding liquid. The responses during learning apparently occur because reward is not yet reliably predicted by a conditioned phasic stimulus. Because the unpredicted occurrence of reward is of central importance for learning, these responses allow dopamine neurons to play an important role in reward-driven learning.

Animals↗

PubMed2026

The effect of monetary versus point-based rewards on effort-cost decision making in individuals at clinical high risk for psychosis.

OBJECTIVE: The dissemination of inexpensive computerized behavioral tasks indexing amotivation may enhance the assessment of clinical high risk (CHR) across settings. However, the impact of varying reward value in such tasks is unclear. If point-based rewards engage participants, this could improve the scalability of computerized assessments. We tested how point-based rewards versus money impacted effort-cost decision-making in CHR individuals. We further assessed how negative symptom severity and household income interacted with reward-type to impact behavior. METHODS: Participants completed the Effort Expenditure for Reward Task (EEfRT). Participants were randomly assigned to receive either money or points for their performance during the EEfRT. Data from a large sample of CHR (N = 233) individuals and healthy controls (HC; N = 157) were collected. RESULTS: Across diagnostic groups, we observed heightened effort expenditure when money was used as a reward (b = 0.13, p = 0.018). We did not find an interaction of CHR status (b = 0.07, p = 0.845) or negative symptoms (b = 0.01, p = 0.429) with reward-type. Within CHR individuals, heightened negative symptom severity was associated with reduced expended effort (b = -0.03, p = 0.016), regardless of reward type. In an exploratory analysis, we found that individuals in the money condition with relatively high household income expended less effort during high reward, high probability trials (b = -0.24, p = 0.046). CONCLUSIONS: Across CHR and HC individuals, individuals pursuing money expended greater effort. While we did not find a group by reward type interaction, CHR individuals with heightened negative symptom severity expended less effort across trials, replicating prior work. Present findings support further study of point-based rewards in tasks indexing amotivation.

Humans↗

PubMed1999

Serotonin and tolerance to delay of reward in rats.

RATIONALE: Tolerance to delay of gratification, taken to reflect impulsiveness, has been proposed to be under the preferential control of central serotonin (5-HT) processes. OBJECTIVE: The present study further examined the effects of drugs which directly or indirectly alter 5-HT transmission, on behaviour controlled by a delayed positive reinforcer. METHODS: Rats were given the choice in a T-maze between two magnitudes of reward: small (two food pellets) and immediate versus large (ten pellets) but delayed. When a 15-s waiting period was imposed in the arm leading to the large reward, rats selected this arm on 65-70% of the trials. This frequency was reduced to less than 40% when the large reward was delayed by 25 s. RESULTS: In rats whose ascending 5-HT pathways had been lesioned by infusion of 5,7-dihydroxytryptamine (5,7-DHT) into the dorsal raphe, the introduction of the 15-s delay contingency resulted in a transient larger reduction of the frequency of choice of the now-delayed reward, compared to sham operated controls. In contrast, choice behaviour of rats given 5,7-DHT into the substantia nigra did not differ from controls. para-Chlorophenylalanine (pCPA, 150 mg/kg IP, daily for 3 days), a 5-HT synthesis inhibitor, bretazenil (0.5-8 mg/kg IP), a benzodiazepine (BZD) receptor partial agonist, and muscimol (0.25-1 mg/kg IP), a GABA(A) receptor agonist, induced a shift toward immediate reward. In contrast to the other BZDs, alprazolam (1-2 mg/kg IP) enhanced the frequency of choice of the large-but-25 s-delayed reward. Similar increased preference for the large-but-delayed reward was induced by the selective 5-HT reuptake inhibitors, fluoxetine (4-8 mg/kg IP) and fluvoxamine (4 mg/kg IP). The full 5-HT(1A) receptor agonist, 8-OH-DPAT (0.015-0.5 mg/kg IP) enhanced the frequency of choice of the large reward delayed by 25 s, whereas the partial agonists, buspirone (1-4 mg/kg IP), ipsapirone (0.5-1 mg/kg IP) and MDL 73005EF (1-2 mg/kg SC), and the antagonist, WAY 100635 (4 mg/kg SC), reduced the number of choices of the large reward delayed by 15 s. Unexpectedly, WAY 100635 (2 mg/kg), which had no effect on choice whatever the delay, did not counteract the increased tolerance to delay induced by 8-OH-DPAT (0.06 mg/kg) and further reduced the frequency of choice of the large-but- 15 s-delayed reward induced by ipsapirone (0.5 mg/kg). CONCLUSIONS: These effects on tolerance to delay may be accounted for by a subtle balance between the opposing functional consequences of pre- versus post-synaptic 5-HT(1A) receptor activation or blockade. Overall, the present results provide further support to the idea that 5-HT processes participate in the control of impulsive-related behaviour, as assessed from tolerance to delay of reward in this particular T-maze procedure.

5,7-Dihydroxytryptamine↗

PubMed2002

Discounting of delayed rewards in substance abusers: relationship to antisocial personality disorder.

RATIONALE: Delay discounting is associated with impulsivity and drug abuse, and this study evaluated the relationship between discounting of delayed rewards and antisocial personality disorder (ASP). OBJECTIVES: To determine whether discounting is increased in substance abusers with ASP relative to those without; both groups were compared with non-substance-abusing controls. METHODS: Subjects ( n=166) chose between hypothetical monetary amounts available after various delays or immediately. Under one condition, a US $1000 reward was delayed at intervals ranging from 6 h to 25 years. At each delay interval, the immediately available rewards varied from US $1 to US $999 until choices reflected indifference between the smaller immediate and larger delayed rewards. Under a second condition, the delayed reward was US $100, and immediate rewards varied from US $0.10 to US $99.90. RESULTS: In all three groups, hyperbolic discounting functions provided a good fit of the data, and the smaller reward was discounted at a higher rate than the larger reward. Substance abusers discounted delayed rewards at significantly greater rates than controls, and substance abusers with ASP discounted delayed rewards at higher rates than their non-ASP substance-abusing counterparts. Discounting rates were correlated with impulsivity scores on a personality questionnaire. CONCLUSIONS: These results provide further evidence of more rapid discounting of delayed rewards in substance abusers, especially among substance abusers with a co-morbid diagnosis of ASP.

Adult↗

PubMed1982

Action of drugs of abuse on brain reward systems: an update with specific attention to opiates.

In addressing the role that the substrate of brain stimulation reward might play in drug abuse, Wise [47] reviewed evidence relating brain stimulation and psychomotor stimulant reward to dopaminergic but not noradrenergic elements identified with brain reward circuitry. He then speculated that one possible mechanism of opiate, ethanol, barbiturate or benzodiazepine reward might involve a specified disinhibition of the dopaminergic element. He suggested that these drugs might have inhibitory actions on locus coeruleus, which in turn might send an inhibitory projection to the dopaminergic link in reward circuitry. This speculation is challenged with respect to ethanol in the companion article [1] and with respect to opiates in the present article. Recent evidence indicates that the rewarding action of opiates is mediated in the region of the dopaminergic cells of the ventral tegmentum and not in the region of the noradrenergic cells of locus coeruleus. Rewarding opiate injections appear to activate the same or a similar dopaminergic link in brain reward circuitry as that thought to be activated through its afferent inputs in the case of brain stimulation reward and activated at its synaptic terminals in the case of psychomotor stimulant reward. Whether other drugs of abuse activate links in brain reward circuitry which function in parallel or in series with the dopaminergic link identified with opiates and stimulants remains an open question.

Alcohol Drinking↗

PubMed1996

The amygdala modulates memory for changes in reward magnitude: involvement of the amygdaloid GABAergic system.

Rats with bilateral amygdala cannulae were trained to run a straight alley for a large or small food reward. Muscimol (MUS), a GABAA agonist, or bicuculline methiodide (BMI), a GABAA antagonist, were infused into the amygdala immediately after a reward shift. In Experiment 1, rats in the large-reward group were shifted to the small reward and immediately after received an infusion of vehicle or MUS bilaterally into the amygdala. The runway latencies of the shifted vehicle animals were increased in comparison with those of the unshifted controls. In contrast, the shifted MUS (0.0001 nM, but not 0.01 nM) animals displayed latencies that were comparable to those of unshifted animals by the second postshift day. These findings suggest that muscimol dose-dependently attenuated the memory of the reward reduction. In Experiment 2 rats were trained as before except they received bilateral infusions of BMI into the amygdala immediately after reward reduction. The shifted BMI (0.1 nM, but not 0.3 nM) animals displayed increased runway latencies, in comparison with those of shifted vehicle animals, by the second postshift day. These findings suggest that BMI dose-dependently enhanced memory of the reward reduction. In Experiment 3, animals were trained as before except they first experienced a reward increase before receiving post-training injections of vehicle, MUS (0.001 nM) or BMI (0.1 nM). On the next day the reward was reduced. Despite reward reduction, shifted BMI animals persisted displaying low latencies for more trials than did shifted MUS animals. These findings suggest that BMI enhanced memory for the reward increase. More generally, the findings suggest that the amygdala and its GABAergic system is involved in memory consolidation for both positive and negative affective experiences.

Amygdala↗

PubMed2005

Announced rewards counteract the impairment of anticipatory behaviour in socially stressed rats.

It is known that stress can influence the sensitivity to rewarding stimuli. Previous observations revealed that socially stressed rats do not display an appetitive behavioural response in anticipation of a reward. A previous study showed that this insensitivity to rewards (anhedonia) could be restored by chronic administration of an antidepressant. Several lines of evidence exist for the role of dopamine in the mechanism of action of antidepressant treatments concerning their therapeutic effect on anhedonia. Therefore, it was hypothesized that regular activation of the reward system, that involves mesolimbic dopaminergic systems, could counteract the effect of social stress on reward-sensitivity. For this, it was investigated whether a treatment of regular reward announcements could prevent the development of anhedonia. This was confirmed by the result that socially stressed rats that received this treatment were able to display anticipatory behaviour which is characterized by increased activity after presentation of a stimulus that was previously associated with a sucrose reward. Surprisingly, a non-treated socially stressed group, that did not show an anticipatory response for sucrose, did display anticipatory behaviour for another type of reward (enriched cage). It seems that, although one might assume the existence of an anhedonic state based upon the absence of anticipatory activity towards a sucrose reward, this assumption cannot be generalised to other types of reward. It will be discussed whether this might be caused by the highly rewarding properties of the enriched cage which probably has a therapeutical efficacy of its own.

Analysis of Variance↗

PubMed2002

Decision-making and addiction (part II): myopia for the future or hypersensitivity to reward?

On a decision-making instrument known as the "gambling task" (GT), a subgroup of substance dependent individuals (SDI) opted for choices that yield high immediate gains in spite of higher future losses. This resembles the behavior of patients with ventromedial (VM) prefrontal cortex lesions. In this study, we addressed the possibility that hypersensitivity to reward may account for the "myopia" for the future in this subgroup of SDI. We used a variant version of the GT, in which the good decks yielded high immediate punishment but higher delayed reward. The bad decks yielded low immediate punishment and lower delayed reward. We measured the skin conductance response (SCR) of subjects after receiving reward (reward SCR) and during their pondering from which deck to choose (anticipatory SCR). A subgroup of SDI who was not impaired on the original GT performed normally on the variant GT. The subgroup of SDI who was impaired on the original GT showed two levels of performance on the variant GT. One subgroup (36% of the sample) performed poorly on the variant GT, and showed similar behavioral and physiological impairments to VM patients. The other subgroup of SDI (64% of the sample) performed normally on the variant task, but had abnormally large physiological responses to reward, i.e. large SCR after receiving reward (reward SCR) and large SCR in anticipation of outcomes that yield large reward. Thus, the combined cognitive and physiological approach of assessing decision-making characterizes three sub-populations of SDI. One sub-population is without impairments that can be detected by any measure of the GT paradigm. Another sub-population is similar to VM patients in that they are insensitive to the future, both positive and negative. A third sub-population is hypersensitive to reward, so that the presence or the prospect of receiving, reward dominates their behavior.

Adult↗