Sensitivity of the brain to loss aversion during risky gambles

Trait sensitivity to stress and cognitive bias processes in fish: A brief overview

Like other animals, fish have unique personalities that can affect their cognition and responses to environmental stressors. These individual personality differences are often referred to as "behavioural syndromes" or "stress coping styles" and can include personality traits such as boldness, shyness, aggression, exploration, locomotor activity, and sociability. For example, bolder or proactive fish may be more likely to take risks and present lower hypothalamo-pituitary-adrenal/interrenal axis reactivity as compared to shy or reactive individuals. Likewise, learning and memory differ between fish personalities. Reactive or shy individuals tend to have faster learning and better association recall with aversive stimuli, while proactive or bold individuals tend to learn more quickly when presented with appetitive incentives. However, the influence of personality on cognitive processes other than cognitive achievement in fish has been scarcely explored. Cognitive bias tests have been employed to investigate the interplay between emotion and cognition in both humans and animals. Fish present cognitive bias processes (CBP) in which fish's interpretation of stimuli could be influenced by its current emotional state and open to environmental modulation. However, no study in fish has explored whether CBP, like in other species, can be interpreted as long-lasting traits and whether other individual characteristics may explain its variation. We hold the perspective that CBP could serve as a vulnerability factor for the onset, persistence, and recurrence of stress-related disorders. Therefore, studying fish's CBP as a state or trait and its interactions with individual variations may be valuable in future efforts to enhance our understanding of anxiety and stress neurobiology in animal models and humans.

Common and distinct neural substrates of the money illusion in win and loss domains

People often evaluate money based on its face value and overlook its real purchasing power, a phenomenon known as the money illusion. In the present study, using functional magnetic resonance imaging (fMRI) combined with a gambling task, we examined the neural signatures of the money illusion in both win and loss domains. Behavioral results showed that self-reported satisfaction with outcomes was modulated by the face value but not the true value of money in both win and loss domains. At the neural level, activity in the posterior insula was associated with the true value of money in the win domain, but not in the loss domain. Importantly, we found that the ventral striatum, ventromedial prefrontal cortex (vmPFC) and amygdala encoded the money illusion in both domains, indicating a domain-general rather than domain-specific neural signature. Moreover, participants with a larger degree of money illusion at the behavioral level showed stronger functional connectivity between the ventral striatum and ventral anterior cingulate cortex (vACC) in the win domain, but stronger functional connectivity between the ventral striatum and amygdala in the loss domain. Our findings highlight the overlapping and distinct neural substrates underlying the money illusion in the context of wins and losses.

Reduced willingness to invest effort in schizophrenia with high negative symptoms regardless of reward stimulus presentation and reward value

BACKGROUND

Negative symptoms in schizophrenia, which are related to poor functioning, are thought to be grounded on aberrant functioning in the reward system. We aimed to disentangle how negative symptoms and two cognitive aspects of goal-directed behavior, mental representation of reward and reward value, affect willingness to invest effort to attain a reward in schizophrenia.

AIMS AND PROCEDURES

To this purpose, 43 schizophrenia patients and 35 healthy controls were assessed for negative symptoms and general functioning, and completed an effort-based reward task. Patients were split in high and low negative symptoms scorers. A series of ANOVA tests were conducted in order to test the effects of group controlling for representation of reward (Task 1) and balance between reward value and effort (Task 2) on will to invest effort to attain a reward.

MAIN FINDINGS

Schizophrenia patients with high negative symptoms chose to invest lower amounts of effort for a reward compared both to low negative symptoms patients and to controls in both tasks. Neither mental representation of reward (Task 1) nor reward value (Task 2) did differentially affect will to invest effort between-groups.

CONCLUSIONS

These findings suggest that the lower willingness to invest effort observed in schizophrenia patients with high negative symptoms may not be related to cognitive aspects of goal-oriented behavior.

The Effect of Wealth Shocks on Loss Aversion: Behavior and Neural Correlates

Kahneman and Tversky (1979) first demonstrated that when individuals decide whether or not to accept a gamble, potential losses receive more weight than possible gains in the decision. This phenomenon is referred to as loss aversion. We investigated how loss aversion in risky financial decisions is influenced by sudden changes to wealth, employing both behavioral and neurobiological measures. We implemented an fMRI experimental paradigm, based on that employed by Tom et al. (2007). There are two treatments, called RANDOM and CONTINGENT. In RANDOM, the baseline setting, the changes to wealth, referred to as wealth shocks in economics, are independent of the actual choices participants make. Under CONTINGENT, we induce the belief that the changes in income are a consequence of subjects' own decisions. The magnitudes and sequence of the shocks to wealth are identical between the CONTINGENT and RANDOM treatments. We investigated whether more loss aversion existed in one treatment than another. The behavioral results showed significantly greater loss aversion in CONTINGENT compared to RANDOM after a negative wealth shock. No differences were observed in the response to positive shocks. The fMRI results revealed a neural loss aversion network, comprising the bilateral striatum, amygdala and dorsal anterior cingulate cortex that was common to the CONTINGENT and RANDOM tasks. However, the ventral prefrontal cortex, primary somatosensory cortex and superior occipital cortex, showed greater activation in response to a negative change in wealth due to individual's own decisions than when the change was exogenous. These results indicate that striatum activation correlates with loss aversion independently of the source of the shock, and that the ventral prefrontal cortex (vPFC) codes the experimental manipulation of agency in one's actions influencing loss aversion.

Neural loss aversion differences between depression patients and healthy individuals: A functional MRI investigation

Neuroeconomics employs neuroscience techniques to explain decision-making behaviours. Prospect theory, a prominent model of decision-making, features a value function with parameters for risk and loss aversion. Recent work with normal participants identified activation related to loss aversion in brain regions including the amygdala, ventral striatum, and ventromedial prefrontal cortex. However, the brain network for loss aversion in pathologies such as depression has yet to be identified. The aim of the current study is to employ the value function from prospect theory to examine behavioural and neural manifestations of loss aversion in depressed and healthy individuals to identify the neurobiological markers of loss aversion in economic behaviour. We acquired behavioural data and fMRI scans while healthy controls and patients with depression performed an economic decision-making task. Behavioural loss aversion was higher in patients with depression than in healthy controls. fMRI results revealed that the two groups shared a brain network for value function including right ventral striatum, ventromedial prefrontal cortex, and right amygdala. However, the neural loss aversion results revealed greater activations in the right dorsal striatum and the right anterior insula for controls compared with patients with depression, and higher activations in the midbrain region ventral tegmental area for patients with depression compared with controls. These results suggest that while the brain network for loss aversion is shared between depressed and healthy individuals, some differences exist with respect to differential activation of additional areas. Our findings are relevant to identifying neurobiological markers for altered decision-making in the depressed.

Altered cingulo-striatal function underlies reward drive deficits in schizophrenia

Amotivation in schizophrenia is assumed to involve dysfunctional dopaminergic signaling of reward prediction or anticipation. It is unclear, however, whether the translation of neural representation of reward value to behavioral drive is affected in schizophrenia. In order to examine how abnormal neural processing of response valuation and initiation affects incentive motivation in schizophrenia, we conducted functional MRI using a deterministic reinforcement learning task with variable intervals of contingency reversals in 20 clinically stable patients with schizophrenia and 20 healthy controls. Behaviorally, the advantage of positive over negative reinforcer in reinforcement-related responsiveness was not observed in patients. Patients showed altered response valuation and initiation-related striatal activity and deficient rostro-ventral anterior cingulate cortex activation during reward approach initiation. Among these neural abnormalities, rostro-ventral anterior cingulate cortex activation was correlated with positive reinforcement-related responsiveness in controls and social anhedonia and social amotivation subdomain scores in patients. Our findings indicate that the central role of the anterior cingulate cortex is in translating action value into driving force of action, and underscore the role of the cingulo-striatal network in amotivation in schizophrenia.

Psychopharmacological characterisation of the successive negative contrast effect in rats

RATIONALE

Successive negative contrast (SNC) describes a change in the behaviour of an animal following a downshift in the quantitative or qualitative value of an expected reward. This behavioural response has been hypothesised to be linked to affective state, with negative states associated with larger and/or prolonged shifts in behaviour.

OBJECTIVE

This study has investigated whether different psychopharmacological treatments have dissociable actions on the SNC effect in rats and related these findings to their actions on different neurotransmitter systems and affective state.

METHODS

Animals were trained to perform a nose-poke response to obtain a high-value food reward (four pellets). SNC was quantified during devalue sessions in which the reward was reduced to one pellet. Using a within-subject study design, the effects of acute treatment with anxiolytic, anxiogenic, antidepressant and dopaminergic drugs were investigated during both baseline (four pellets) or devalue sessions (one pellet).

RESULTS

The indirect dopamine agonist, amphetamine, attenuated the SNC effect whilst the D1/D2 antagonist, alpha-flupenthixol, potentiated it. The antidepressant citalopram, anxiolytic buspirone and anxiogenic FG7142 had no specific effects on SNC, although FG7142 induced general impairments at higher doses. The α2-adrenoceptor antagonist, yohimbine, increased premature responding but had no specific effect on SNC. Results for the anxiolytic diazepam were mixed with one group showing an attenuation of the SNC effect whilst the other showed no effect.

CONCLUSIONS

These data suggest that the SNC effect is mediated, at least in part, by dopamine signalling. The SNC effect may also be attenuated by benzodiazepine anxiolytics.

Association between white matter fiber structure and reward-related reactivity of the ventral striatum

Individual responsiveness to rewards or rewarding stimuli may affect various domains of normal as well as pathological behavior. The ventral striatum/nucleus accumbens (NAcc) constitutes a key brain structure in the regulation of reward-appetitive behavior. It remains unclear, however, to which extent individual reward-related BOLD response in the NAcc is dependent on individual characteristics of connecting white matter fiber tracts. Using tract-based spatial statistics (TBSS) and statistical parametric mapping (SPM) this combined DTI - fMRI study investigated this question by correlating NAcc BOLD signal upon receipt of a monetary reward with different white matter characteristics (FA, axial diffusivity, radial diffusivity). The results show that increased integrity of white matter as assessed by FA in the cingulate and corpus callosum, the inferior fronto-occipital fasciculus, the anterior thalamic radiation and the anterior limb of the internal capsule was positively correlated with reward-related activation in the NAcc. There were no negative correlations as well as no significant results regarding axial and radial diffusivity. These findings indicate that microstructural properties of fiber tracts connecting, amongst others, the cortex with the striatum may influence intensity of reward-related responsiveness of the ventral striatum by constraining or increasing efficiency in information transfer within relevant circuitries involved in processing of reward.

Modulation of working memory function by motivation through loss-aversion

Cognitive performance is affected by motivation. Few studies, however, have investigated the neural mechanisms of the influence of motivation through potential monetary punishment on working memory. We employed functional MRI during a delayed recognition task that manipulated top-down control demands with added monetary incentives to some trials in the form of potential losses of bonus money. Behavioral performance on the task was influenced by loss-threatening incentives in the form of faster and more accurate performance. As shown previously, we found enhancement of activity for relevant stimuli occurs throughout all task periods (e.g., stimulus encoding, maintenance, and response) in both prefrontal and visual association cortex. Further, these activation patterns were enhanced for trials with possible monetary loss relative to nonincentive trials. During the incentive cue, the amygdala and striatum showed significantly greater activation when money was at a possible loss on the trial. We also evaluated patterns of functional connectivity between regions responsive to monetary consequences and prefrontal areas responsive to the task. This analysis revealed greater delay period connectivity between and the left insula and prefrontal cortex with possible monetary loss relative to nonincentive trials. Overall, these results reveal that incentive motivation can modulate performance on working memory tasks through top-down signals via amplification of activity within prefrontal and visual association regions selective to processing the perceptual inputs of the stimuli to be remembered.

Mine and me: exploring the neural basis of object ownership

Previous research has shown that encoding information in the context of self-evaluation leads to memory enhancement, supported by activation in ventromedial pFC. Recent evidence suggests that similar self-memory advantages can be obtained under nonevaluative encoding conditions, such as when object ownership is used to evoke self-reference. Using fMRI, the current study explored the neural correlates of object ownership. During scanning, participants sorted everyday objects into self-owned or other-owned categories. Replicating previous research, a significant self-memory advantage for the objects was observed (i.e., self-owned > other-owned). In addition, encoding self-owned items was associated with unique activation in posterior dorsomedial pFC (dMPFC), left insula, and bilateral supramarginal gyri (SMG). Subsequent analysis showed that activation in a subset of these regions (dMPFC and left SMG) correlated with the magnitude of the self-memory advantage. Analysis of the time-to-peak data suggested a temporal model for processing ownership in which initial activation of dMPFC spreads to SMG and insula. These results indicate that a self-memory advantage can be elicited by object ownership and that this effect is underpinned by activity in a neural network that supports attentional, reward, and motor processing.

Microstructural brain differences predict functional hemodynamic responses in a reward processing task

Many aspects of human behavior are driven by rewards, yet different people are differentially sensitive to rewards and punishment. In this study, we show that white matter microstructure in the uncinate/inferior fronto-occipital fasciculus, defined by fractional anisotropy values derived from diffusion tensor magnetic resonance images, correlates with both short-term (indexed by the fMRI blood oxygenation level-dependent response to reward in the nucleus accumbens) and long-term (indexed by the trait measure sensitivity to punishment) reactivity to rewards. Moreover, trait measures of reward processing were also correlated with reward-related functional activation in the nucleus accumbens. The white matter tract revealed by the correlational analysis connects the anterior temporal lobe with the medial and lateral orbitofrontal cortex and also supplies the ventral striatum. The pattern of strong correlations suggests an intimate relationship between white matter structure and reward-related behavior that may also play a role in a number of pathological conditions, such as addiction and pathological gambling.

Reward networks in the brain as captured by connectivity measures

An assortment of human behaviors is thought to be driven by rewards including reinforcement learning, novelty processing, learning, decision making, economic choice, incentive motivation, and addiction. In each case the ventral tegmental area/ventral striatum (nucleus accumbens) (VTA–VS) system has been implicated as a key structure by functional imaging studies, mostly on the basis of standard, univariate analyses. Here we propose that standard functional magnetic resonance imaging analysis needs to be complemented by methods that take into account the differential connectivity of the VTA–VS system in the different behavioral contexts in order to describe reward based processes more appropriately. We first consider the wider network for reward processing as it emerged from animal experimentation. Subsequently, an example for a method to assess functional connectivity is given. Finally, we illustrate the usefulness of such analyses by examples regarding reward valuation, reward expectation and the role of reward in addiction.

Functional neuroimaging of reward circuitry responsivity to monetary gains and losses in posttraumatic stress disorder

BACKGROUND

Clinical impressions and preclinical work suggest that posttraumatic stress disorder (PTSD) might be associated with dysfunctional reward processing. To pursue this issue, we administered a validated passive-viewing monetary reward task during functional magnetic resonance imaging (fMRI) to subjects with chronic PTSD and to mentally healthy individuals.

METHODS

The protocol evaluated fMRI signal changes that anticipated or accompanied monetary gains and losses under varying conditions of controlled expectation. The "expectancy phase" entailed presentation of a promising, unpromising, or intermediate Wheel of Fortune-type spinner, whereas the "outcome phase" was defined by the arrow landing on one of three sectors of that spinner, thereby determining the subjects' gain or loss for that trial.

RESULTS

Neuroimaging data from 20 PTSD and 26 healthy subjects withstood quality control procedures and were included. In voxelwise and anatomically defined region-of-interest analyses, when gains were contrasted to losses, between-group comparison revealed smaller bilateral striatal activations in the PTSD subjects. In the PTSD group, less striatal activation to gains versus losses was associated with more self-reported motivational and social deficits.

CONCLUSIONS

The present data support the hypothesis that PTSD is associated with abnormal processing of monetary outcomes and that this alteration might be related to some aspects of emotional numbing.

The role of serotonin in nonnormative risky choice: the effects of tryptophan supplements on the "reflection effect" in healthy adult volunteers

Risky decision-making involves weighing good and bad outcomes against their probabilities in order to determine the relative values of candidate actions. Although human decision-making sometimes conforms to rational models of how this weighting is achieved, irrational (or nonnormative) patterns of risky choice, including shifts between risk-averse and risk-seeking choices involving equivalent-value gambles (the "reflection effect"), are frequently observed. In the present experiment, we investigated the role of serotonin in decision-making under conditions of uncertainty. Fifteen healthy adult volunteers received a treatment of 3 g per day of the serotonin precursor, tryptophan, in the form of dietary supplements over a 14-day period, whereas 15 age- and IQ-matched control volunteers received a matched placebo substance. At test, all participants completed a risky decision-making task involving a series of choices between two simultaneously presented gambles, differing in the magnitude of their possible gains, the magnitude of their possible losses, and the probabilities with which these outcomes were delivered. Tryptophan supplements were associated with alterations in the weighting of gains and small losses perhaps reflecting reduced loss-aversion, and a marked and significant diminution of the reflection effect. We conclude that serotonin activity plays a significant role in nonnormative risky decision-making under conditions of uncertainty.

Functional connectivity of reward processing in the brain

Controversial results have been reported concerning the neural mechanisms involved in the processing of rewards and punishments. On the one hand, there is evidence suggesting that monetary gains and losses activate a similar fronto-subcortical network. On the other hand, results of recent studies imply that reward and punishment may engage distinct neural mechanisms. Using functional magnetic resonance imaging (fMRI) we investigated both regional and interregional functional connectivity patterns while participants performed a gambling task featuring unexpectedly high monetary gains and losses. Classical univariate statistical analysis showed that monetary gains and losses activated a similar fronto-striatal-limbic network, in which main activation peaks were observed bilaterally in the ventral striatum. Functional connectivity analysis showed similar responses for gain and loss conditions in the insular cortex, the amygdala, and the hippocampus that correlated with the activity observed in the seed region ventral striatum, with the connectivity to the amygdala appearing more pronounced after losses. Larger functional connectivity was found to the medial orbitofrontal cortex for negative outcomes. The fact that different functional patterns were obtained with both analyses suggests that the brain activations observed in the classical univariate approach identifies the involvement of different functional networks in the current task. These results stress the importance of studying functional connectivity in addition to standard fMRI analysis in reward-related studies.

Do you make a difference? Social context in a betting task

Social context strongly influences human motivated behavior. The triadic model implicates three major nodes in the regulation of motivated behavior, i.e. amygdala, medial prefrontal cortex (mPFC) and striatum. The present work examines how social context modulates this system. Nineteen healthy subjects completed an event-related functional magnetic resonance imaging study of a monetary betting task in the presence (social trials) and in the absence of a social peer (nonsocial trials). In the social trials, the scanned subject played along with another subject, although their performances were independent from one another. In the nonsocial trials the scanned subject played alone. Although behavioral performance did not differ between social and nonsocial trials, BOLD signal changes during betting were significantly greater in the amygdala bilaterally and the right dorsolateral prefrontal cortex (BA 9) in the social condition relative to the nonsocial condition. In contrast, activation was greater in ventral striatum in the nonsocial condition relative to the social condition. These findings suggest that social context modulates the triadic neural-systems ensemble to adjust motivated behavior to the unique demands associated with the presence of conspecifics.

Sensitivity to reward loss as an indicator of animal emotion and welfare

The scientific study of animal emotion is an important emerging discipline in subjects ranging from neuroscience to animal welfare research. In the absence of direct measures of conscious emotion, indirect behavioural and physiological measures are used. However, these may have significant limitations (e.g. indicating emotional arousal but not valence (positivity versus negativity)). A new approach, taking its impetus from human studies, proposes that biases in information processing, and underlying mechanisms relating to the evaluation of reward gains and losses, may reliably reflect emotional valence in animals. In general, people are more sensitive to reward losses than gains, but people in a negative affective state (e.g. depression) are particularly sensitive to losses. This may underlie broader findings such as an enhanced attention to, and memory of, negative events in depressed individuals. Here we show that rats in unenriched housing, who typically exhibit indicators of poorer welfare and a more negative affective state than those in enriched housing, display a prolonged response to a decrease in anticipated food reward, indicating enhanced sensitivity to reward loss. Sensitivity to reward reduction may thus be a valuable new indicator of animal emotion and welfare.