Can Personality Type Explain Heterogeneity in Probability Distortions?

There are two regularities we have learned from experimental studies of choice under risk. The first is that the majority of people weigh objective probabilities non-linearly. The second regularity, although less commonly acknowledged, is that there is a large amount of heterogeneity in how people distort probabilities. Despite of this, little effort has been made to identify the source of heterogeneity. In this paper, we explore the possibility that personality type is linked to probability distortions. Using validated psychological questionnaires, we clustered participants into distinct personality types: motivated, impulsive, and affective. We found that the motivated viewed gambling more attractive, whereas the impulsive were the most capable of discriminating non-extreme probabilities. Our results suggest that the observed heterogeneity in probability distortions may be explained by personality profiles, which can be elicited though standard psychological questionnaires.

Differential neurobiological effects of expert advice on risky choice in adolescents and adults.

We investigated behavioral and neurobiological mechanisms by which risk-averse advice, provided by an expert, affected risky decisions across three developmental groups [early adolescents (12-14 years), late adolescents (15-17 years), adults (18+ years)]. Using cumulative prospect theory, we modeled choice behavior during a risky-choice task. Results indicate that advice had a significantly greater impact on risky choice in both adolescent groups than in adults. Using functional magnetic resonance imaging, we investigated the neural correlates of this behavioral effect. Developmental effects on correlations between brain activity and valuation parameters were obtained in regions that can be classified into (i) cognitive control regions, such as dorsolateral prefrontal cortex (DLPFC) and ventrolateral PFC; (ii) social cognition regions, such as posterior temporoparietal junction; and (iii) reward-related regions, such as ventromedial PFC (vmPFC) and ventral striatum. Within these regions, differential effects of advice on neural correlates of valuation were observed across development. Specifically, advice increased the correlation strength between brain activity and parameters reflective of safe choice options in adolescent DLPFC and decreased correlation strength between activity and parameters reflective of risky choice options in adult vmPFC. Taken together, results indicate that, across development, distinct brain systems involved in cognitive control and valuation mediate the risk-reducing effect of advice during decision making under risk via specific enhancements and reductions of the correlation strength between brain activity and valuation parameters.

The price of your soul: neural evidence for the non-utilitarian representation of sacred values.

Sacred values, such as those associated with religious or ethnic identity, underlie many important individual and group decisions in life, and individuals typically resist attempts to trade off their sacred values in exchange for material benefits. Deontological theory suggests that sacred values are processed based on rights and wrongs irrespective of outcomes, while utilitarian theory suggests that they are processed based on costs and benefits of potential outcomes, but which mode of processing an individual naturally uses is unknown. The study of decisions over sacred values is difficult because outcomes cannot typically be realized in a laboratory, and hence little is known about the neural representation and processing of sacred values. We used an experimental paradigm that used integrity as a proxy for sacredness and which paid real money to induce individuals to sell their personal values. Using functional magnetic resonance imaging (fMRI), we found that values that people refused to sell (sacred values) were associated with increased activity in the left temporoparietal junction and ventrolateral prefrontal cortex, regions previously associated with semantic rule retrieval. This suggests that sacred values affect behaviour through the retrieval and processing of deontic rules and not through a utilitarian evaluation of costs and benefits.

Neural insensitivity to upticks in value is associated with the disposition effect.

The disposition effect is a phenomenon in which investors hold onto losing assets longer than they hold onto gaining assets. In this study, we used functional magnetic resonance imaging (fMRI) to measure the response of valuation regions in the brain during the decision to keep or to sell an asset that followed a random walk in price. The most common explanation for the disposition effect is preference-based: namely, that people are risk-averse over gains and risk-seeking over losses. This explanation would predict correlations between individuals' risk-preferences, the magnitude of their disposition effect, and activation in valuation structures of the brain. We did not observe these correlations. Nor did we find evidence for a realization utility explanation, which would predict differential responses in valuation regions during the decision to sell versus keep an asset that correlated with the magnitude of the disposition effect. Instead, we found an attenuated ventral striatum response to upticks in value below the purchase price in some individuals with a large disposition effect. Given the role of the striatum in signaling prediction error, the blunted striatal response is consistent with the expectation that an asset will rise when it is below the purchase price, thus spurring loss-holding behavior. This suggests that for some individuals, the disposition effect is likely driven by a belief that the asset will eventually return to the purchase price, also known as mean reversion.

From bad to worse: striatal coding of the relative value of painful decisions.

The majority of decision-related research has focused on how the brain computes decisions over outcomes that are positive in expectation. However, much less is known about how the brain integrates information when all possible outcomes in a decision are negative. To study decision-making over negative outcomes, we used fMRI along with a task in which participants had to accept or reject 50/50 lotteries that could result in more or fewer electric shocks compared to a reference amount. We hypothesized that behaviorally, participants would treat fewer shocks from the reference amount as a gain, and more shocks from the reference amount as a loss. Furthermore, we hypothesized that this would be reflected by a greater BOLD response to the prospect of fewer shocks in regions typically associated with gain, including the ventral striatum and orbitofrontal cortex. The behavioral data suggest that participants in our study viewed all outcomes as losses, despite our attempt to induce a status quo. We find that the ventral striatum showed an increase in BOLD response to better potential gambles (i.e., fewer expected shocks). This lends evidence to the idea that the ventral striatum is not solely responsible for reward processing but that it might also signal the relative value of an expected outcome or action, regardless of whether the outcome is entirely appetitive or aversive. We also find a greater response to worse gambles in regions previously associated with aversive valuation, suggesting an opposing but simultaneous valuation signal to that conveyed by the striatum.

Neural mechanisms of the influence of popularity on adolescent ratings of music.

It is well-known that social influences affect consumption decisions. We used functional magnetic resonance imaging (fMRI) to elucidate the neural mechanisms associated with social influence with regard to a common consumer good: music. Our study population was adolescents, age 12-17. Music is a common purchase in this age group, and it is widely believed that adolescent behavior is influenced by perceptions of popularity in their reference group. Using 15-s clips of songs from MySpace.com, we obtained behavioral measures of preferences and neurobiological responses to the songs. The data were gathered with, and without, the overall popularity of the song revealed. Song popularity had a significant effect on the participants' likability ratings of the songs. fMRI results showed a strong correlation between the participants' rating and activity in the caudate nucleus, a region previously implicated in reward-driven actions. The tendency to change one's evaluation of a song was positively correlated with activation in the anterior insula and anterior cingulate, two regions that are associated with physiological arousal and negative affective states. Sensitivity to popularity was linked to lower activation levels in the middle temporal gyrus, suggesting a lower depth of musical semantic processing. Our results suggest that a principal mechanism whereby popularity ratings affect consumer choice is through the anxiety generated by the mismatch between one's own preferences and others'. This mismatch anxiety motivates people to switch their choices in the direction of the consensus. Our data suggest that this is a major force behind the conformity observed in music tastes in some teenagers.

Adolescent engagement in dangerous behaviors is associated with increased white matter maturity of frontal cortex.

BACKGROUND: Myelination of white matter in the brain continues throughout adolescence and early adulthood. This cortical immaturity has been suggested as a potential cause of dangerous and impulsive behaviors in adolescence. METHODOLOGY/PRINCIPAL FINDINGS: We tested this hypothesis in a group of healthy adolescents, age 12-18 (N = 91), who underwent diffusion tensor imaging (DTI) to delineate cortical white matter tracts. As a measure of real-world risk taking, participants completed the Adolescent Risk Questionnaire (ARQ) which measures engagement in dangerous activities. After adjusting for age-related changes in both DTI and ARQ, engagement in dangerous behaviors was found to be positively correlated with fractional anisotropy and negatively correlated with transverse diffusivity in frontal white matter tracts, indicative of increased myelination and/or density of fibers (ages 14-18, N = 60). CONCLUSIONS/SIGNIFICANCE: The direction of correlation suggests that rather than having immature cortices, adolescents who engage in dangerous activities have frontal white matter tracts that are more adult in form than their more conservative peers.

Expert financial advice neurobiologically "Offloads" financial decision-making under risk.

BACKGROUND: Financial advice from experts is commonly sought during times of uncertainty. While the field of neuroeconomics has made considerable progress in understanding the neurobiological basis of risky decision-making, the neural mechanisms through which external information, such as advice, is integrated during decision-making are poorly understood. In the current experiment, we investigated the neurobiological basis of the influence of expert advice on financial decisions under risk. METHODOLOGY/PRINCIPAL FINDINGS: While undergoing fMRI scanning, participants made a series of financial choices between a certain payment and a lottery. Choices were made in two conditions: 1) advice from a financial expert about which choice to make was displayed (MES condition); and 2) no advice was displayed (NOM condition). Behavioral results showed a significant effect of expert advice. Specifically, probability weighting functions changed in the direction of the expert's advice. This was paralleled by neural activation patterns. Brain activations showing significant correlations with valuation (parametric modulation by value of lottery/sure win) were obtained in the absence of the expert's advice (NOM) in intraparietal sulcus, posterior cingulate cortex, cuneus, precuneus, inferior frontal gyrus and middle temporal gyrus. Notably, no significant correlations with value were obtained in the presence of advice (MES). These findings were corroborated by region of interest analyses. Neural equivalents of probability weighting functions showed significant flattening in the MES compared to the NOM condition in regions associated with probability weighting, including anterior cingulate cortex, dorsolateral PFC, thalamus, medial occipital gyrus and anterior insula. Finally, during the MES condition, significant activations in temporoparietal junction and medial PFC were obtained. CONCLUSIONS/SIGNIFICANCE: These results support the hypothesis that one effect of expert advice is to "offload" the calculation of value of decision options from the individual's brain.

Neurobiological regret and rejoice functions for aversive outcomes.

A decision maker may experience regret when a choice he makes results in a more adverse outcome than a different choice would have yielded. Analogously, he may experience rejoice when his choice resulted in better outcomes. We used fMRI to investigate the neural correlates of regret and rejoice where payoffs are in terms of a non-monetary medium. Incentives were created using painful outcomes in the form of mild electrical shocks to the foot and the possibility of avoiding them. We hypothesized that the neural response to a painful outcome resulting from an individual's choice would also reflect the degree of regret as measured by the likelihood that alternative choices would have yielded the same adverse outcome. Similarly, when an individual avoids a potential shock, he would experience a degree of rejoice that correlates with the probability he had of receiving the shock. For example, winning a bet when winning was unlikely, even if the outcome is the same, evokes more rejoice than winning when it was highly probable. Our results suggest that activation of a cortical network, consisting of the medial orbitofrontal cortex, left superior frontal cortex, right angular gyrus, and left thalamus, correlates with the degree of regret. A different network, including the rostral anterior cingulate, left hippocampus, left ventral striatum, and brain stem/midbrain correlated with rejoice. The right inferior orbitofrontal cortex, pre-supplementary motor area, anterior cingulate, and posterior cingulate showed similar patterns of activation with both regret and rejoice, suggesting that these regions may be associated with surprise from the realization of relatively unlikely events. Our results suggest that distinct, but overlapping networks are involved in the experiences of regret and rejoice.

Nonlinear neurobiological probability weighting functions for aversive outcomes.

While mainstream economic models assume that individuals treat probabilities objectively, many people tend to overestimate the likelihood of improbable events and underestimate the likelihood of probable events. However, a biological account for why probabilities would be treated this way does not yet exist. While undergoing fMRI, we presented individuals with a series of lotteries, defined by the voltage of an impending cutaneous electric shock and the probability with which the shock would be received. During the prospect phase, neural activity that tracked the probability of the expected outcome was observed in a circumscribed network of brain regions that included the anterior cingulate, visual, parietal, and temporal cortices. Most of these regions displayed responses to probabilities consistent with nonlinear probability weighting. The neural responses to passive lotteries predicted 79% of subsequent decisions when individuals were offered choices between different lotteries, and exceeded that predicted by behavior alone near the indifference point.

Three studies on the neuroeconomics of decision-making when payoffs are real and negative.

PURPOSE: We summarize three previous neuroeconomic studies with two features that distinguish them from most others in experimental economics: (1) the use of physical pain to induce incentives and (2) acquisition of data on brain activation levels. By correlating behavior when payoffs are painful with brain activation, we are able to test for the neurobiological relevance of important phenomena previously observed in experimental studies that are at odds with classical economic theories of decision-making. These specific phenomena are (a) negative discounting of future payoffs; (b) nonlinear probability weighting; (c) the experience of regret and rejoice when making a decision under risk. METHODOLOGY/APPROACH: The expectation of pain is created through the use of mild electric shocks to the top of the foot. Pain confers disutility, so decisions are made in the domain of losses relative to the status quo. Simultaneous with these decisions, brain activation data is acquired through functional magnetic resonance imaging (fMRI). FINDINGS: We find evidence for negative time discounting of electric shocks. Participants who exhibited the most extreme forms of this discounting were distinguished by early and robust activation of a subset of the cortical pain matrix. We also find evidence for probability weighting in the domain of electric shocks, which is manifest at the neural level. We find evidence both behaviorally and neurally for regret and rejoice functions for painful outcomes. ORIGINALITY/VALUE OF CHAPTER: Previous experimental economic studies in the domain of losses have typically used monetary rewards. Here, we report behavioral effects and neural correlates using pain.

Receptor theory and biological constraints on value.

Modern economic theories of value derive from expected utility theory. Behavioral evidence points strongly toward departures from linear value weighting, which has given rise to alternative formulations that include prospect theory and rank-dependent utility theory. Many of the nonlinear forms for value assumed by these theories can be derived from the assumption that value is signaled by neurotransmitters in the brain, which obey simple laws of molecular movement. From the laws of mass action and receptor occupancy, we show how behaviorally observed forms of nonlinear value functions can arise.

Multicomponent collection as of 2005.

Multicomponent apheresis (MCA) begun in Genoa in 1985 in autologous terms. Named "sequestration" it was the preoperative collection of autologous components (RBC-plasma-platelets) using the same apparatus and harness ready for intraoperative blood salvage. In 1986 the technique was applied to donor platelet apheresis with the goal of reducing the costs of platelet collection and concurrently reducing the risks of viral disease transmission to haematological patients who did receive, in the same transfusion event, the necessary blood components obtained from the same donor. The results of this application were maximized by the so called aggressive MCA by which in selected donors, it is possible to collect 2 units of platelets along with 1 or 2 units of PRBCs. These applications were made possible by the development of the concept of dry-platelet collection according to which platelets are collected in only 20-25 mL of plasma and subsequently resuspended in non-plasma solutions such as T-Sol. A last development of MCC is for RBC apheresis, with the collection of 1-2 units of RBC independently of platelet collection. This is going to be the first step of apheresis as the unique modality of collecting blood leaving the bags to history of blood transfusion. Interestingly it took 15 years to MCC to be rediscovered and appreciated worldwide both for its intrinsic cost saving capabilities offered along with an increasing safety for patients. In terms of donor acceptance it is our experience that, since 1989 no donor has refused MCC, consisting at least in the concurrent collection of plasma along with platelets, but also RBC and or a second unit of platelets.

Trimethoprim-sulfamethoxazole-induced aseptic meningitis: case report and literature review.

Aseptic meningitis is a rare adverse drug reaction, reported with non-steroidal anti-inflammatory agents (NSAIDs) and with miscellaneous drugs such as trimethoprim-sulfamethoxazole (TMP-SMX). The most common clinical findings reported are fever, headache, stiffness and altered level of consciousness. We report a case of aseptic meningitis related to TMP-SMX ingestion that caused severe derangements of the patient's vital signs, requiring Intensive Care Unit admittance. The prompt diagnosis and discontinuation of the drug resulted in complete recovery. We examine the case according to the literature on this topic. We conclude that, since the signs and symptoms of this unusual drug reaction may mimic those of central nervous system infection, the clinician should consider this etiology when he is faced with a patient with suspected meningoencephalitis, especially if the latter has already been treated at home with unknown drugs. Further studies should investigate the pathogenetic mechanism of TMP-SMX-induced aseptic meningitis.

Morphological heterogeneity with normal expression but altered function of G proteins in porcine cultured regenerated coronary endothelial cells.

1. Experiments were designed to investigate whether the pertussis toxin-dependent endothelial dysfunction following balloon injury is due to a reduced expression or an insufficient function of G-proteins. 2. Endothelium-dependent responses of porcine coronary arteries were examined in vitro by use of conventional organ chambers. Morphological analysis was performed by isolating and culturing the endothelial cells from these arteries. The expression of Gi-proteins in regenerated endothelial cells was measured by Western blots and immunolabelling. The function of G-proteins was assessed by measuring the GTPase activity of cultured endothelial cells. 3. Eight days following denudation, endothelial regrowth was confirmed by histological examination and by demonstrating the presence of endothelium-dependent relaxations to bradykinin and 5-hydroxytryptamine (5-HT). In primary culture, the regenerated endothelial cells displayed a 'cobblestone' pattern as seen with native endothelial cells. 4. Twenty eight days after denudation, the endothelium-dependent relaxations induced by 5-HT were impaired, but those to bradykinin were maintained. However, the latter were reduced when endothelium-dependent hyperpolarization was prevented. 5. Twenty eight days after denudation, multinucleated giant cells were present in the regenerated but not in the native cultured endothelial cell populations. These regenerated endothelial cells incorporated less tritiated thymidine than native endothelial cells. 6. The intensities of the bands on the immunoblot of the regenerated endothelial cells, when several antibodies against Gi alpha 1/alpha 2/alpha 3 were used, were the same as those obtained in native endothelial cells. The immunolabelling with the same antibodies was similar between the giant cells and the regenerated endothelial cells of normal size. The hydrolysis of GTP was lower in regenerated than in native endothelial cell membranes. 7. In conclusion, endothelium-dependent relaxations mediated by Gi-proteins are impaired in balloon denuded coronary arteries. This dysfunction following regeneration cannot be explained by a reduced expression of Gi proteins but rather reflects an abnormal function of the G-proteins in the regenerated endothelium.

[Preanesthesia in elderly patients undergoing subarachnoid anesthesia: chlordesmethyldiazepam versus diazepam]. / La preanestesia nei soggetti anziani sottoposti ad anestesia sub-aracnoidea: clordemetildiazepam vs diazepam.

Forty patients over 65 undergoing subarachnoid anesthesia with bupivacaine 0.50% (5 mg) and fentanyl (0.1 mg) were subdivided into two equal groups: one was premedicated with atropine and chlordesmethyldiazepam (0.03 mg/kg-1) and the other with atropine and diazepam (0.015 mg/Kg-1). A statistically significant difference was found in the group treated with diazepam which required an increase for anesthetic drugs during surgery. The authors suggest a probable synergic or an enhanced effect between intramuscular chlordesmethyldiazepam and opiates in spinal anesthesia.

Single-donor platelet concentrates produced along with packed red blood cells with the Haemonetics MCS 3p: preliminary results.

There has been an increasing interest in recent years over the qualitative superiority of single-donor platelets in the management of hemato-oncologic patients. The reasonable desire of both patients and physicians to limit the risks of transfusion along with the need for limiting the costs involved in this kind of therapy have led to application of multicomponent donations both in terms of double platelet concentrates and double products such as red blood cells (RBC) and platelets from the same donor. Single donor platelets and RBC have been collected in a semi-automated mode and only the very recent introduction of the Haemonetics MCS 3p with its SDP/RBC protocol provides a totally closed-system automated protocol for this combined collection. Twenty procedures have been carried out so far at our unit. In a mean of 87 minutes (6-7 passes), a mean of 3.1 x 10(11) platelets were collected along with approximately 220 mL of packed RBC. The leukocyte contamination of the platelet product was in the range of 0.4-1.1 x 10(7) (99% lymphocytes), and the quality of platelets was very satisfactory as measured by the hypotonic shock response, aggregation induced by ADP, collagen and ristocetin, morphology score, and membrane glycoproteins modifications. Equally satisfactory was the quality of the RBC concentrate, suspended in 80 mL of SAG-M, with a total hemoglobin (Hb) content approaching 55 g as compared to the normal Hb content of a standard RBC concentrate that is approximately 62 g.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of nimesulide and diclofenac in the prevention and treatment of painful inflammatory postoperative complications of general surgery.

In a double-blind study, 40 patients scheduled for saphenectomy or inguinal hernioplasty were randomly assigned to treatment with nimesulide (200mg 3 times daily) or diclofenac (100mg 3 times daily) administered rectally. Therapy with either drug resulted in significantly less pain, oedema and hyperaemia, and resolution of mild fever. No adverse reactions attributable to treatment were observed.