Phineas gauged: decision-making and the human prefrontal cortex

Affective judgment and beneficial decision making: ventromedial prefrontal activity correlates with performance in the Iowa Gambling Task

Damasio proposes in his somatic marker theory that not only cognitive but also affective components are critical for decision making. Since affective judgment requires an interplay between affective and cognitive components, it might be considered a key process in decision making that has been linked to neural activity in ventromedial prefrontal cortex (VMPFC). Using functional magnetic resonance imaging (fMRI), we examined the relationship between VMPFC, emotionally (unexpected)- and cognitively (expected)-accentuated affective judgment, and beneficial decision making (Iowa Gambling Task; IGT) in healthy subjects. Neuronal activity in the VMPFC during unexpected affective judgment significantly correlated with both global and final performance in the IGT task. These findings suggest that the degree to which subjects recruit the VMPFC during affective judgment is related to beneficial performance in decision making in gambling.

On Framing Effects in Decision Making: Linking Lateral versus Medial Orbitofrontal Cortex Activation to Choice Outcome Processing

Two correlates of outcome processing in the orbitofrontal cortex (OFC) have been proposed in the literature: One hypothesis suggests that the lateral/medial division relates to representation of outcome valence (negative vs. positive), and the other suggests that the medial OFC maintains steady stimulus-outcome associations, whereas the lateral OFC represents changing (unsteady) outcomes to prepare for response shifts. These two hypotheses were contrasted by comparing the original with the inverted version of the Iowa Gambling Task in an event-related functional magnetic resonance imaging experiment. Results showed (1) that (caudo) lateral OFC was indeed sensitive to the steadiness of the outcomes and not merely to outcome valence and (2) that the original and the inverted tasks, although both designed to measure sensitivity for future outcomes, were not equivalent as they enacted different behaviors and brain activation patterns. Results are interpreted in terms of Kahneman and Tversky's prospect theory suggesting that cognitions and decisions are biased differentially when probabilistic future rewards are weighed against consistent punishments relative to the opposite scenario [Kahneman, D., & Tversky, A. Choices, values, and frames. American Psychologist, 39, 341–350, 1984]. Specialized processing of unsteady rewards (involving caudolateral OFC) may have developed during evolution in support of goal-related thinking, prospective planning, and problem solving.

Deciding how to decide: ventromedial frontal lobe damage affects information acquisition in multi-attribute decision making

Ventromedial frontal lobe (VMF) damage is associated with impaired decision making. Recent efforts to understand the functions of this brain region have focused on its role in tracking reward, punishment and risk. However, decision making is complex, and frontal lobe damage might be expected to affect it at other levels. This study used process-tracing techniques to explore the effect of VMF damage on multi-attribute decision making under certainty. Thirteen subjects with focal VMF damage were compared with 11 subjects with frontal damage that spared the VMF and 21 demographically matched healthy control subjects. Participants chose rental apartments in a standard information board task drawn from the literature on normal decision making. VMF subjects performed the decision making task in a way that differed markedly from all other groups, favouring an 'alternative-based' information acquisition strategy (i.e. they organized their information search around individual apartments). In contrast, both healthy control subjects and subjects with damage predominantly involving dorsal and/or lateral prefrontal cortex pursued primarily 'attribute-based' search strategies (in which information was acquired about categories such as rent and noise level across several apartments). This difference in the pattern of information acquisition argues for systematic differences in the underlying decision heuristics and strategies employed by subjects with VMF damage, which in turn may affect the quality of their choices. These findings suggest that the processes supported by ventral and medial prefrontal cortex need to be conceptualized more broadly, to account for changes in decision making under conditions of certainty, as well as uncertainty, following damage to these areas.

The somatic marker hypothesis: A critical evaluation

The somatic marker hypothesis (SMH; [Damasio, A. R., Tranel, D., Damasio, H., 1991. Somatic markers and the guidance of behaviour: theory and preliminary testing. In Levin, H.S., Eisenberg, H.M., Benton, A.L. (Eds.), Frontal Lobe Function and Dysfunction. Oxford University Press, New York, pp. 217-229]) proposes that emotion-based biasing signals arising from the body are integrated in higher brain regions, in particular the ventromedial prefrontal cortex (VMPFC), to regulate decision-making in situations of complexity. Evidence for the SMH is largely based on performance on the Iowa Gambling Task (IGT; [Bechara, A., Tranel, D., Damasio, H., Damasio, A.R., 1996. Failure to respond autonomically to anticipated future outcomes following damage to prefrontal cortex. Cerebral Cortex 6 (2), 215-225]), linking anticipatory skin conductance responses (SCRs) to successful performance on a decision-making paradigm in healthy participants. These 'marker' signals were absent in patients with VMPFC lesions and were associated with poorer IGT performance. The current article reviews the IGT findings, arguing that their interpretation is undermined by the cognitive penetrability of the reward/punishment schedule, ambiguity surrounding interpretation of the psychophysiological data, and a shortage of causal evidence linking peripheral feedback to IGT performance. Further, there are other well-specified and parsimonious explanations that can equally well account for the IGT data. Next, lesion, neuroimaging, and psychopharmacology data evaluating the proposed neural substrate underpinning the SMH are reviewed. Finally, conceptual reservations about the novelty, parsimony and specification of the SMH are raised. It is concluded that while presenting an elegant theory of how emotion influences decision-making, the SMH requires additional empirical support to remain tenable.

Behavioral and neural predictors of upcoming decisions

Although it is widely known that brain regions such as the prefrontal cortex, the amygdala, and the ventral striatum play large roles in decision making, their precise contributions remain unclear. Here, we used functional magnetic resonance imaging and principles of reinforcement learning theory to investigate the relationship between current reinforcements and future decisions. In the experiment, subjects chose between high-risk (i.e., low probability of a large monetary reward) and low-risk (high probability of a small reward) decisions. For each subject, we estimated value functions that represented the degree to which reinforcements affected the value of decision options on the subsequent trial. Individual differences in value functions predicted not only trial-to-trial behavioral strategies, such as choosing high-risk decisions following high-risk rewards, but also the relationship between activity in prefrontal and subcortical regions during one trial and the decision made in the subsequent trial. These findings provide a novel link between behavior and neural activity by demonstrating that value functions are manifested both in adjustments in behavioral strategies and in the neural activity that accompanies those adjustments.

Investment behavior and the negative side of emotion

Can dysfunction in neural systems subserving emotion lead, under certain circumstances, to more advantageous decisions? To answer this question, we investigated how normal participants, patients with stable focal lesions in brain regions related to emotion (target patients), and patients with stable focal lesions in brain regions unrelated to emotion (control patients) made 20 rounds of investment decisions. Target patients made more advantageous decisions and ultimately earned more money from their investments than the normal participants and control patients. When normal participants and control patients either won or lost money on an investment round, they adopted a conservative strategy and became more reluctant to invest on the subsequent round; these results suggest that they were more affected than target patients by the outcomes of decisions made in the previous rounds.

Acute effects of alprazolam on risky decision making in humans

RATIONALE

GABA-A receptor ligands, including benzodiapines, may induce disinhibitory effects that increase the probability of risky decision making. To date, few laboratory studies have examined the acute, dose-related effects of benzodiazepines on human risk-taking behavior. Recent data indicate that in the United States alprazolam is the benzodiazepine most frequently misused for recreational purposes.

OBJECTIVES

The present study was designed to demonstrate a dose-response relationship between acute alprazolam administration and human risk taking. Furthermore, this investigation sought to examine: (1) the behavioral mechanisms that may be involved in changes in the probability of risky decision making related to alprazolam administration and (2) risk seeking-related personality variables that may predict drug effects on risk taking.

METHODS

Using a laboratory measure of risk taking designed to address acute drug effects, 16 adults were administered placebo, 0.5, 1.0, and 2.0 mg alprazolam in a within-subject repeated-measures design. The risk-taking task presented subjects with a choice between two response options operationally defined as risky and nonrisky. Data analyses examined subjective effects, response rates, distribution of choices between the risky and nonrisky option, trial-by-trial response probabilities, and personality correlates related to drug effects at the 2.0-mg dose.

RESULTS

Alprazolam administration produced dose-related changes in subjective effects, response rates, and, most importantly, dose-dependently increased selection of the risky response option. The 2.0-mg dose increased the probability of making consecutive risky responses following a gain on the risky response option. Increases at 2.0 mg were related to a combination of personality scales that included high venturesomeness and novelty seeking and low harm avoidance.

CONCLUSIONS

Alprazolam administration produced increases in human risk taking under laboratory conditions. In union with previous studies, the observed shift in trial-by-trial response probabilities suggests that sensitivity to consequences (e.g., oversensitivity to recent rewards) may be an important mechanism in the psychopharmacology of risky decision making. Additionally, risk-seeking personality traits may be predictive of acute drug effects on risk-taking behavior.

Neuroeconomics: an overview from an economic perspective

Until now, economic theory has not systematically integrated the influence of emotions on decision-making. Since evidence from neuroscience suggests that decision-making as hypothesized in economic theory depends on prior emotional processing, interdisciplinary research under the label of "neuroeconomics" arose. The key idea of this approach is to employ recent neuroscientific methods in order to analyze economically relevant brain processes. This paper aims to provide an overview of the current state of neuroeconomic research by giving a brief description of the concept of neuroeconomics, outlining methods commonly used and describing current studies in this new research area. Finally, some future prospects and limitations are discussed.

Decision-making deficits of korsakoff patients in a new gambling task with explicit rules: associations with executive functions

Decision-making deficits reflected by risky decisions in gambling tasks have been associated with frontal lobe dysfunctions in various neurologic and psychiatric populations. The question remains whether decision-making impairments are related to executive functions. The authors developed a new gambling task, the Game of Dice Task, with explicit and stable rules for reinforcement and punishment, to investigate relations between executive functions and risk-taking behavior in an explicit decision-making situation. A sample of 35 alcoholic Korsakoff patients and 35 healthy controls was examined with the Game of Dice Task and a neuropsychological test battery. Results show that Korsakoff patients are strongly impaired in this explicit decision-making task and that these disturbances are correlated with specific executive functions.

The dark side of emotion in decision-making: when individuals with decreased emotional reactions make more advantageous decisions

Can dysfunction in neural systems subserving emotion lead, under certain circumstances, to more advantageous decisions? To answer this question, we investigated how individuals with substance dependence (ISD), patients with stable focal lesions in brain regions related to emotion (lesion patients), and normal participants (normal controls) made 20 rounds of investment decisions. Like lesion patients, ISD made more advantageous decisions and ultimately earned more money from their investments than the normal controls. When normal controls either won or lost money on an investment round, they adopted a conservative strategy and became more reluctant to invest on the subsequent round, suggesting that they were more affected than lesion patients and ISD by the outcomes of decisions made in the previous rounds.

Functional connectivity with anterior cingulate and orbitofrontal cortices during decision-making

Recent neuroscience research is beginning to discover the brain regions involved in decision-making under uncertainty, but little is known about whether or how these regions functionally interact with each other. Here, we used event-related functional magnetic resonance imaging to examine both changes in overall activity and changes in functional connectivity during risk-taking. Results showed that choosing high-risk over low-risk decisions was associated with increased activity in both anterior cingulate and orbitofrontal cortices. Connectivity analyses revealed that largely distinct, but somewhat overlapping, cortical and subcortical regions exhibited significant functional connectivity with anterior cingulate and orbitofrontal cortices. Additionally, connectivity with the anterior cingulate in some regions, including the orbitofrontal cortex and nucleus accumbens, was modulated by the decision participants chose. These findings (1) elucidate large networks of brain regions that are functionally connected with both anterior cingulate and orbitofrontal cortices during decision-making and (2) demonstrate that the roles of orbitofrontal and anterior cingulate cortices can be functionally differentiated by examining patterns of connectivity.

Neural basis for generalized quantifier comprehension

Generalized quantifiers like "all cars" are semantically well understood, yet we know little about their neural representation. Our model of quantifier processing includes a numerosity device, operations that combine number elements and working memory. Semantic theory posits two types of quantifiers: first-order quantifiers identify a number state (e.g. "at least 3") and higher-order quantifiers additionally require maintaining a number state actively in working memory for comparison with another state (e.g. "less than half"). We used BOLD fMRI to test the hypothesis that all quantifiers recruit inferior parietal cortex associated with numerosity, while only higher-order quantifiers recruit prefrontal cortex associated with executive resources like working memory. Our findings showed that first-order and higher-order quantifiers both recruit right inferior parietal cortex, suggesting that a numerosity component contributes to quantifier comprehension. Moreover, only probes of higher-order quantifiers recruited right dorsolateral prefrontal cortex, suggesting involvement of executive resources like working memory. We also observed activation of thalamus and anterior cingulate that may be associated with selective attention. Our findings are consistent with a large-scale neural network centered in frontal and parietal cortex that supports comprehension of generalized quantifiers.

Social and emotional decision-making following frontal lobe injury

Neuropsychological, psychophysiological and functional imaging research has begun to offer insights into the everyday difficulties in decision-making experienced by some patients with frontal lobe damage. It is widely accepted that the ventral prefrontal cortex plays a pivotal role in social and emotional decision-making. This article will review experimental findings using the Iowa Gambling Task and the Cambridge Gamble Task that explore the brain mechanisms of decision-making. Convergent evidence from the two tasks confirms the importance of ventral PFC, but also highlights the relevance of lesion laterality, lesion aetiology, and the contribution of other brain regions (including the dorsal prefrontal cortex and amygdala) to decision-making abilities. The extent to which disrupted decision-making can be separated from the broader domain of executive function is discussed.