Neural valuation of rewards and punishments in posttraumatic stress disorder: a computational approach

Posttraumatic stress disorder (PTSD) is associated with changes in fear learning and decision-making, suggesting involvement of the brain's valuation system. Here we investigate the neural mechanisms of subjective valuation of rewards and punishments in combat veterans. In a functional MRI study, male combat veterans with a wide range of posttrauma symptoms (N = 48, Clinician Administered PTSD Scale, CAPS-IV) made a series of choices between sure and uncertain monetary gains and losses. Activity in the ventromedial prefrontal cortex (vmPFC) during valuation of uncertain options was associated with PTSD symptoms, an effect which was consistent for gains and losses, and specifically driven by numbing symptoms. In an exploratory analysis, computational modeling of choice behavior was used to estimate the subjective value of each option. The neural encoding of subjective value varied as a function of symptoms. Most notably, veterans with PTSD exhibited enhanced representations of the saliency of gains and losses in the neural valuation system, especially in ventral striatum. These results suggest a link between the valuation system and the development and maintenance of PTSD, and demonstrate the significance of studying reward and punishment processing within subject.

Value-based decision making under uncertainty in hoarding and obsessive- compulsive disorders

Difficulties in decision making are a core impairment in a range of disease states. For instance, both obsessive- compulsive disorder (OCD) and hoarding disorder (HD) are associated with indecisiveness, inefficient planning, and enhanced uncertainty intolerance, even in contexts unrelated to their core symptomology. We examined decision-making patterns in 19 individuals with OCD, 19 individuals with HD, 19 individuals with comorbid OCD and HD, and 57 individuals from the general population, using a well-validated choice task grounded in behavioral economic theory. Our results suggest that difficulties in decision making in individuals with OCD (with or without comorbid HD) are linked to reduced fidelity of value-based decision making (i.e. increase in inconsistent choices). In contrast, we find that performance of individuals with HD on our laboratory task is largely intact. Overall, these results support our hypothesis that decision-making impairments in OCD and HD, which can appear quite similar clinically, have importantly different underpinnings. Systematic investigation of different aspects of decision making, under varying conditions, may shed new light on commonalities between and distinctions among clinical syndromes.

POSTTRAUMATIC STRESS SYMPTOMS AND AVERSION TO AMBIGUOUS LOSSES IN COMBAT VETERANS

BACKGROUND

Psychiatric symptoms typically cut across traditional diagnostic categories. In order to devise individually tailored treatments, there is a need to identify the basic mechanisms that underlie these symptoms. Behavioral economics provides a framework for studying these mechanisms at the behavioral level. Here, we utilized this framework to examine a widely ignored aspect of trauma-related symptomatology-individual uncertainty attitudes-in combat veterans with and without posttraumatic stress disorder (PTSD).

METHODS

Fifty-seven combat veterans, including 30 with PTSD and 27 without PTSD, completed a risk and ambiguity decision-making task that characterizes individual uncertainty attitudes, distinguishing between attitudes toward uncertain outcomes with known ("risk") and unknown ("ambiguity") probabilities, and between attitudes toward uncertain gains and uncertain losses. Participants' choices were used to estimate risk and ambiguity attitudes in the gain and loss domains.

RESULTS

Veterans with PTSD were more averse to ambiguity, but not risk, compared to veterans without PTSD, when making choices between possible losses, but not gains. The degree of aversion was associated with anxious arousal (e.g., hypervigilance) symptoms, as well as with the degree of combat exposure. Moreover, ambiguity attitudes fully mediated the association between combat exposure and anxious arousal symptoms.

CONCLUSIONS

These results provide a foundation for prospective studies of the causal association between ambiguity attitudes and trauma-related symptoms, as well as etiologic studies of the neural underpinnings of these behavioral outcomes. More generally, these results demonstrate the potential of neuroeconomic and behavioral economic techniques for devising objective and incentive-compatible diagnostic tools, and investigating the etiology of psychiatric disorders.

Not sensitive, yet less biased: A signal detection theory perspective on mindfulness, attention, and recognition memory

The practice of mindfulness has been argued to increase attention control and improve memory performance. However, it was recently suggested that the effect of mindfulness on memory may be due to a shift in response-bias, rather than to an increase in memory-sensitivity. The present study examined the mindfulness-attention-memory triad. Participants filled in the five-facets of mindfulness questionnaire, and completed two recognition blocks; in the first attention was full, whereas in the second attention was divided during the encoding of information. It was found that the facet of non-judging (NJ) moderated the impact of attention on memory, such that responses of high NJ participants were less biased and remained constant even when attention was divided. Facets of mindfulness were not associated with memory sensitivity. These findings suggest that mindfulness may affect memory through decision making processes, rather than through directing attentional resources to the encoding of information.

Decision-making under uncertainty in obsessive-compulsive disorder

Obsessive compulsive disorder (OCD) produces profound morbidity. Difficulties with decision-making and intolerance of uncertainty are prominent clinical features in many patients. The nature and etiology of these deficits are poorly understood. We used a well-validated choice task, grounded in behavioral economic theory, to investigate differences in valuation and value-based choice during decision making under uncertainty in 20 unmedicated participants with OCD and 20 matched healthy controls. Participants' choices were used to assess individual decision-making characteristics. OCD participants did not differ from healthy controls in how they valued uncertain options when outcome probabilities were known (risk) but were more likely than healthy controls to avoid uncertain options when these probabilities were imprecisely specified (ambiguity). Compared to healthy controls, individuals with OCD were less consistent in their choices and less able to identify options that should be clearly preferable. These abnormalities correlated with symptom severity. These results suggest that value-based choices during decision-making are abnormal in OCD. Individuals with OCD show elevated intolerance of uncertainty, but only when outcome probabilities are themselves uncertain. Future research focused on the neural valuation network, which is implicated in value-based computations, may provide new neurocognitive insights into the pathophysiology of OCD. Deficits in decision-making processes may represent a target for therapeutic intervention.

Emotional context influences access of visual stimuli to anxious individuals' awareness

Anxiety has been associated with enhanced unconscious processing of threat and attentional biases towards threat. Here, we focused on the phenomenology of perception in anxiety and examined whether threat-related material more readily enters anxious than non-anxious individuals' awareness. In six experiments, we compared the stimulus exposures required for each anxiety group to become objectively or subjectively aware of masked facial stimuli varying in emotional expression. Crucially, target emotion was task irrelevant. We found that high trait-anxiety individuals required less sensory evidence (shorter stimulus exposure times) to become aware of the face targets. This anxiety-based difference was observed for fearful faces in all experiments, but with non-threat faces, it emerged only when these were presented among threatening faces. Our findings suggest a prominent role for affective context in high-anxiety individuals' conscious perception of visual stimuli. Possible mechanisms underlying the influence of context in lowering awareness thresholds in anxious individuals are discussed.

Grouping does not require attention

Many theories of visual perception stipulate that Gestalt grouping occurs preattentively. Subjects' failure to report perceiving even salient grouping patterns under conditions of inattention challenges this assumption (see, e.g., Mack, Tang, Tuma, Kahn, & Rock, 1992), but Moore and Egeth (1997) showed that although subjects are indeed unable to identify grouping patterns outside the focus of attention, effects of these patterns on visual perception can be observed when they are assessed using implicit, rather than explicit, measures. However, this finding, which is the only one to date demonstrating grouping effects without attention, is open to an alternative account. In the present study, we eliminated this confound and replicated Moore and Egeth's findings, using the Müller-Lyer illusion (Experiments 1 and 2). Moreover, we found converging evidence for these findings with a variant of the flanker task (Experiment 3), when the amount of available attentional resources was varied (Experiments 4 and 5). The results reinforce the idea that, although grouping outside the focus of attention cannot be the object of overt report, grouping processes can occur without attention.