John Monterosso

Maximizing versus satisficing: happiness is a matter of choice.

Can people feel worse off as the options they face increase? The present studies suggest that some people--maximizers--can. Study 1 reported a Maximization Scale, which measures individual differences in desire to maximize. Seven samples revealed negative correlations between maximization and happiness, optimism, self-esteem, and life satisfaction, and positive correlations between maximization and depression, perfectionism, and regret. Study 2 found maximizers less satisfied than nonmaximizers (satisficers) with consumer decisions, and more likely to engage in social comparison. Study 3 found maximizers more adversely affected by upward social comparison. Study 4 found maximizers more sensitive to regret and less satisfied in an ultimatum bargaining game. The interaction between maximizing and choice is discussed in terms of regret, adaptation, and self-blame.

Striatal Dopamine D2/D3 Receptor Availability Is Reduced in Methamphetamine Dependence and Is Linked to Impulsivity

While methamphetamine addiction has been associated with both impulsivity and striatal dopamine D2/D3 receptor deficits, human studies have not directly linked the latter two entities. We therefore compared methamphetamine-dependent and healthy control subjects using the Barratt Impulsiveness Scale (version 11, BIS-11) and positron emission tomography with [18F]fallypride to measure striatal dopamine D2/D3 receptor availability. The methamphetamine-dependent subjects reported recent use of the drug 3.3 g per week, and a history of using methamphetamine, on average, for 12.5 years. They had higher scores than healthy control subjects on all BIS-11 impulsiveness subscales (p < 0.001). Volume-of-interest analysis found lower striatal D2/D3 receptor availability in methamphetamine-dependent than in healthy control subjects (p < 0.01) and a negative relationship between impulsiveness and striatal D2/D3 receptor availability in the caudate nucleus and nucleus accumbens that reached statistical significance in methamphetamine-dependent subjects. Combining data from both groups, voxelwise analysis indicated that impulsiveness was related to D2/D3 receptor availability in left caudate nucleus and right lateral putamen/claustrum (p < 0.05, determined by threshold-free cluster enhancement). In separate group analyses, correlations involving the head and body of the caudate and the putamen of methamphetamine-dependent subjects and the lateral putamen/claustrum of control subjects were observed at a weaker threshold (p < 0.12 corrected). The findings suggest that low striatal D2/D3 receptor availability may mediate impulsive temperament and thereby influence addiction.

Beyond discounting: possible experimental models of impulse control

Abstractu2002Animal studies of impulsivity have typically used one of three models: a delay of reward procedure, a differential reinforcement for low rate responding (DRL) procedure, or an autoshaping procedure. In each of these paradigms, we argue, measurement of impulsivity is implicitly or explicitly equated with the effect delay has on the value of reward. The steepness by which delay diminishes value (the temporal discount function) is treated as an index of impulsivity. In order to provide a better analog of human impulsivity, this model needs to be expanded to include the converse of impulsivity – self-control. Through mechanisms such as committing to long range interests before the onset of temptation, or through bundling individual choices into classes of choices that are made at once, human decision-making can often look far less myopic than single trial experiments predict. For people, impulsive behavior may be more often the result of the breakdown of self-control mechanisms than of steep discount functions. Existing animal models of self-control are discussed, and future directions are suggested for psychopharmacological research.

Frontoparietal cortical activity of methamphetamine-dependent and comparison subjects performing a delay discounting task.

Relative to individuals who do not have addictive disorders, drug abusers exhibit greater devaluation of rewards as a function of their delay (“delay discounting”). The present study sought to extend this finding to methamphetamine (MA) abusers and to help understand its neural basis. MA abusers (n = 12) and control subjects who did not use illicit drugs (n = 17) participated in tests of delay discounting with hypothetical money rewards. We then used a derived estimate of each individuals delay discounting to generate a functional magnetic resonance imaging probe task consisting of three conditions: “hard choices,” requiring selections between “smaller, sooner” and “larger, later” alternatives that were similarly valued given the individuals delay discounting; “easy choices,” in which alternatives differed dramatically in value; and a “no choice” control condition. MA abusers exhibited more delay discounting than control subjects (P < 0.05). Across groups, the “hard choice > no choice” contrast revealed significant effects in the ventrolateral prefrontal cortex, dorsolateral prefrontal cortex (DLPFC), dorsal anterior cingulate cortex, and areas surrounding the intraparietal sulcus (IPS). With group comparisons limited to these clusters, the “hard choice > easy choice” contrast indicated significant group differences in task‐related activity within the left DLPFC and right IPS; qualitatively similar nonsignificant effects were present in the other clusters tested. Whereas control subjects showed less recruitment associated with easy than with hard choices, MA abusers generally did not. Correlational analysis did not indicate a relationship between this anomaly in frontoparietal recruitment and greater degree of delay discounting exhibited by MA abusers. Therefore, while apparent inefficiency of cortical processing related to decision‐making in MA abusers may contribute to the neural basis of enhanced delay discounting by this population, other factors remain to be identified. Hum. Brain Mapp, 2007.

Neural Substrates of Resisting Craving during Cigarette Cue Exposure

BACKGROUNDnIn cigarette smokers, the most commonly reported areas of brain activation during visual cigarette cue exposure are the prefrontal, anterior cingulate, and visual cortices. We sought to determine changes in brain activity in response to cigarette cues when smokers actively resist craving.nnnMETHODSnForty-two tobacco-dependent smokers underwent functional magnetic resonance imaging, during which they were presented with videotaped cues. Three cue presentation conditions were tested: cigarette cues with subjects allowing themselves to crave (cigarette cue crave), cigarette cues with the instruction to resist craving (cigarette cue resist), and matched neutral cues.nnnRESULTSnActivation was found in the cigarette cue resist (compared with the cigarette cue crave) condition in the left dorsal anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), and precuneus. Lower magnetic resonance signal for the cigarette cue resist condition was found in the cuneus bilaterally, left lateral occipital gyrus, and right postcentral gyrus. These relative activations and deactivations were more robust when the cigarette cue resist condition was compared with the neutral cue condition.nnnCONCLUSIONSnSuppressing craving during cigarette cue exposure involves activation of limbic (and related) brain regions and deactivation of primary sensory and motor cortices.

Comparing attentional bias to smoking cues in current smokers, former smokers, and non-smokers using a dot-probe task

Much evidence documents that individuals with emotional and drug-use disorders demonstrate biased attention toward stimuli associated with their disorder. This bias appears to diminish following successful treatment. Two studies examined whether current cigarette smokers show biased attention toward smoking-related images compared with non-smokers (Studies 1 and 2) and whether this bias is less pronounced in former smokers (Study 2). Attentional bias toward cigarette-related photographs was examined using the dot-probe task. Pairs of images (one smoking-related) appeared side by side for 500 ms on a computer screen prior to the presentation of a probe (an asterisk) replacing one of the photographs. Subjects struck a key as quickly as possible to indicate the probe location. Attentional bias was defined as faster reaction times when the probe replaced the smoking-related image. In both studies, current smokers displayed significantly greater attentional bias toward cigarette stimuli than did non-smokers. Former smokers in Study 2 displayed an intermediate level of bias, but did not differ significantly in bias score from either of the other groups. These results support further use of the dot-probe task as a measure of attentional bias in non-abstinent smokers and in individuals undergoing smoking cessation treatment.

Predicting treatment response to naltrexone: the influence of craving and family history.

Naltrexone has repeatedly been shown to reduce drinking in alcohol-dependent patients. Previous clinical research suggests that naltrexone may be more effective at reducing drinking among patients with high levels of alcohol craving at the beginning of treatment. In addition, laboratory studies suggest that naltrexone may be more efficacious among patients with a high familial loading of alcohol problems. We explored both of these possibilities in the context of the first 12-week phase of a double blind, placebo-controlled naltrexone trial. A total of 121 patients were randomized to receive 100 mg/day naltrexone and 62 patients were randomized to receive placebo. Both naltrexone and placebo were given in conjunction with a psychosocial intervention designed to be integrated with the use of pharmacotherapy. This intervention was administered by nurse practitioners. Overall, patients randomized to naltrexone reported drinking five or more drinks on fewer days than did placebo controls (p = .04). Interactions were observed between medication group assignment and both craving level prior to randomization (p = .02) and family loading of alcohol problems (p = .05). In both cases, the interaction was in the predicted direction. These data suggest that patients with high levels of alcohol craving or a strong family history of alcoholism are more likely to benefit from naltrexone treatment.

Leptin replacement alters brain response to food cues in genetically leptin-deficient adults

A missense mutation in the ob gene causes leptin deficiency and morbid obesity. Leptin replacement to three adults with this mutation normalized body weight and eating behavior. Because the neural circuits mediating these changes were unknown, we paired functional magnetic resonance imaging (fMRI) with presentation of food cues to these subjects. During viewing of food-related stimuli, leptin replacement reduced brain activation in regions linked to hunger (insula, parietal and temporal cortex) while enhancing activation in regions linked to inhibition and satiety (prefrontal cortex). Leptin appears to modulate feeding behavior through these circuits, suggesting therapeutic targets for human obesity.

Striatal Dopamine D2/D3 Receptors Mediate Response Inhibition and Related Activity in Frontostriatal Neural Circuitry in Humans

Impulsive behavior is thought to reflect a traitlike characteristic that can have broad consequences for an individuals success and well-being, but its neurobiological basis remains elusive. Although striatal dopamine D2-like receptors have been linked with impulsive behavior and behavioral inhibition in rodents, a role for D2-like receptor function in frontostriatal circuits mediating inhibitory control in humans has not been shown. We investigated this role in a study of healthy research participants who underwent positron emission tomography with the D2/D3 dopamine receptor ligand [18F]fallypride and BOLD fMRI while they performed the Stop-signal Task, a test of response inhibition. Striatal dopamine D2/D3 receptor availability was negatively correlated with speed of response inhibition (stop-signal reaction time) and positively correlated with inhibition-related fMRI activation in frontostriatal neural circuitry. Correlations involving D2/D3 receptor availability were strongest in the dorsal regions (caudate and putamen) of the striatum, consistent with findings of animal studies relating dopamine receptors and response inhibition. The results suggest that striatal D2-like receptor function in humans plays a major role in the neural circuitry that mediates behavioral control, an ability that is essential for adaptive responding and is compromised in a variety of common neuropsychiatric disorders.

Different Forms of Self-Control Share a Neurocognitive Substrate

Psychological and neurocognitive studies have suggested that different kinds of self-control may share a common psychobiological component. If this is true, performance in affective and nonaffective inhibitory control tasks in the same individuals should be correlated and should rely upon integrity of this region. To test this hypothesis, we acquired high-resolution magnetic resonance images from 44 healthy and 43 methamphetamine-dependent subjects. Individuals with methamphetamine dependence were tested because of prior findings that they suffer inhibitory control deficits. Gray matter structure of the inferior frontal gyrus was assessed using voxel-based morphometry. Subjects participated in tests of motor and affective inhibitory control (stop-signal task and emotion reappraisal task, respectively); and methamphetamine-dependent subjects provided self-reports of their craving for methamphetamine. Performance levels on the two inhibitory control tasks were correlated with one another and with gray matter intensity in the right pars opercularis region of the inferior frontal gyrus in healthy subjects. Gray matter intensity of this region was also correlated with methamphetamine craving. Compared with healthy subjects, methamphetamine-dependent subjects exhibited lower gray matter intensity in this region, worse motor inhibitory control, and less success in affect regulation. These findings suggest that self-control in different psychological domains involves a common substrate in the right pars opercularis, and that successful self-control depends on integrity of this substrate.