Neural processing of food cues in pre-pubertal children.

BACKGROUND/OBJECTIVES: Neuroimaging investigations of brain pathways involved in reward and motivation have primarily focused on adults. This study sought to identify brain responses to visual food cues and explore its relationships with adiposity and sex in pre-pubertal children. METHODS: Brain responses to palatable food vs. non-food cues were measured in 53 children (age: 8.18 ± .66 years; sex: 22 boys, 31 girls) after an overnight fast. Whole-brain analysis (cluster-correction Z > 2.3, P < .05) was performed to examine brain food cue reactivity and its relationships with adiposity and sex. RESULTS: Greater brain activity in response to food vs. non-food cues was observed in regions implicated in reward (orbital frontal cortex, striatum), taste (insula, postcentral gyrus), appetite (hypothalamus), emotion (amygdala), memory (hippocampus), visual processing (occipital cortex) and attention (parietal cortex). A negative association was found between percent body fat and food cue reactivity in the medial prefrontal cortex and lateral orbital frontal cortex adjusting for age and sex. Boys compared with girls had increased food cue reactivity in right hippocampus and visual cortex. CONCLUSIONS: These data suggest that body fat and sex are important moderators of brain food cue reactivity in children.

Changes in cerebral glucose metabolism during early abstinence from chronic methamphetamine abuse.

Changes in brain function during the initial weeks of abstinence from chronic methamphetamine abuse may substantially affect clinical outcome, but are not well understood. We used positron emission tomography with [F-18]fluorodeoxyglucose (FDG) to quantify regional cerebral glucose metabolism, an index of brain function, during performance of a vigilance task. A total of 10 methamphetamine-dependent subjects were tested after 5-9 days of abstinence, and after 4 additional weeks of supervised abstinence. A total of 12 healthy control subjects were tested at corresponding times. Global glucose metabolism increased between tests (P=0.01), more in methamphetamine-dependent (10.9%, P=0.02) than control subjects (1.9%, NS). Glucose metabolism did not change in subcortical regions of methamphetamine-dependent subjects, but increased in neocortex, with maximal increase (>20%) in parietal regions. Changes in reaction time and self-reports of negative affect varied more in methamphetamine-dependent than in control subjects, and correlated both with the increase in parietal glucose metabolism, and decrease in relative activity (after scaling to the global mean) in some regions. A robust relationship between change in self-reports of depressive symptoms and relative activity in the ventral striatum may have great relevance to treatment success because of the role of this region in drug abuse-related behaviors. Shifts in cortical-subcortical metabolic balance either reflect new processes that occur during early abstinence, or the unmasking of effects of chronic methamphetamine abuse that are obscured by suppression of cortical glucose metabolism that continues for at least 5-9 days after cessation of methamphetamine self-administration.

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.

Three decision-making tasks in cocaine-dependent patients: do they measure the same construct?

AIMS: Substance-abusing populations perform poorly on decision-making tasks related to delay and risk. These tasks include: (1) the Delay Discounting Procedure (DDP), in which choices are made between smaller-sooner and later-larger rewards, (2) the Gambling Task (GT), in which choices are made between alternatives varying in pay-off and punishment, and (3) the Rogers Decision-Making Task (RDMT) in which subjects choose between higher or lower probability gambles. We examine the interrelationship among these tasks. DESIGN: A test battery was created which included the DDP, GT and RDMT, as well as measures of impulsivity, intellectual functioning and drug use. SETTING: Subjects completed the test battery at an outpatient center, prior to beginning 12 weeks of treatment. PARTICIPANTS: Thirty-two treatment-seeking cocaine dependent individuals (primarily African-American males) participated. FINDINGS: Performance on the GT was significantly correlated with performance on the DDP (r = 0.37; p = 0.04). Reaction times on the RDMT correlated with performance on the GT (r = 0.36, p = 0.04) and DDP (r = 0.33, p = 0.07), but actual choices on the RDMT did not (p > 0.9 for both). While no significant relationships were observed between task performance and impulsivity, IQ estimate was positively correlated with both the GT (r = 0.44, p = 0.01) and RDMT (r = 0.41, p = 0.021). Split half reliability data indicated higher reliability when using only data from the latter half of the GT (r = 0.92 vs. r = 0.80). CONCLUSIONS: These data offer preliminary evidence of overlap in the decision-making functioning tapped by these tasks. Possible implications for drug-taking behavior are discussed.

Psychosocially enhanced treatment for cocaine-dependent mothers: evidence of efficacy.

Eighty-four cocaine-dependent mothers were randomly assigned either to a case management-oriented outpatient treatment program (CM), or to a psychosocially enhanced treatment program (PET). Both programs included onsite child care and both offered daily group therapy sessions. Subjects randomized to the PET condition were offered a variety of additional onsite services designed to meet their special psychosocial needs including parenting skills class, access to a psychiatrist, individual therapy sessions, and GED class. Patients in the CM program could gain access to these services only through referrals to community resources. Program retention was significantly better for patients in the PET condition. In addition, while the mean number of days of cocaine use decreased from baseline in both groups, the PET group had significantly fewer days of cocaine use at 12-month follow-up than the CM group. These results show that providing psychosocial enhancement services onsite can improve treatment outcome for cocaine-dependent mothers.

Beyond discounting: possible experimental models of impulse control.

Animal 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.