[show abstract][hide abstract] ABSTRACT: Attention-deficit/hyperactivity disorder (ADHD) is a prevalent psychiatric disorder that has poor long-term outcomes and remains a major public health concern. Recent theories have proposed that ADHD arises from alterations in multiple neural pathways. Alterations in reward circuits are hypothesized as one core dysfunction, leading to altered processing of anticipated rewards. The nucleus accumbens (NAcc) is particularly important for reward processes; task-based fMRI studies have found atypical activation of this region while the participants performed a reward task. Understanding how reward circuits are involved with ADHD may be further enhanced by considering how the NAcc interacts with other brain regions. Here we used the technique of resting-state functional connectivity MRI (rs-fcMRI) to examine the alterations in the NAcc interactions and how they relate to impulsive decision making in ADHD. Using rs-fcMRI, this study: examined differences in functional connectivity of the NAcc between children with ADHD and control children; correlated the functional connectivity of NAcc with impulsivity, as measured by a delay discounting task; and combined these two initial segments to identify the atypical NAcc connections that were associated with impulsive decision making in ADHD. We found that functional connectivity of NAcc was atypical in children with ADHD and the ADHD-related increased connectivity between NAcc and the prefrontal cortex was associated with greater impulsivity (steeper delayed-reward discounting). These findings are consistent with the hypothesis that atypical signaling of the NAcc to the prefrontal cortex in ADHD may lead to excessive approach and failure in estimating future consequences; thus, leading to impulsive behavior.
European neuropsychopharmacology: the journal of the European College of Neuropsychopharmacology 11/2012; · 3.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: When offered a choice between a small monetary reward available immediately (SmallNow) versus a larger reward available after a delay (LargeLater), smokers select the SmallNow alternative more than nonsmokers. That is, smokers discount the value of the LargeLater reward more than nonsmokers.
To investigate whether this group difference was due to smokers overweighting the value of rewards available immediately compared with nonsmokers, we examined whether the group difference was also seen when both alternatives were delayed, i.e., when choosing between a SmallSoon reward and a LargeLater reward.
In Experiment 1, smokers and nonsmokers completed a task including SmallNow versus LargeLater choices and SmallSoon versus LargeLater choices. In Experiment 2, smokers and nonsmokers completed the same task but with hypothetical choices.
Analyses using hyperbolic and double exponential (β-δ) models replicate prior findings that smokers discount the LargeLater reward more than nonsmokers when the smaller reward is available immediately. The smoker-nonsmoker difference was also seen when the smaller reward was slightly delayed, though this effect was primarily driven by heightened discounting in male smokers. However, for potentially real rewards only, this smoker-nonsmoker difference was significantly reduced when the smaller reward was delayed.
The smoker-nonsmoker difference in discounting is not confined to situations involving immediate rewards. Differences associated with potentially real versus hypothetical rewards and gender underscore the complexity of the smoking-delay discounting relationship.
[show abstract][hide abstract] ABSTRACT: Persons with severe and persistent mental illnesses, e.g. schizophrenia spectrum disorders and bipolar disorder, smoke at a much higher rate than the general population. Treatment options for schizophrenia spectrum disorders and bipolar disorder often include the first-generation (typical) and second-generation (atypical) antipsychotics, which have been shown to be effective in treating both psychotic and mood symptoms. This article reviews studies examining the relationship between antipsychotic medication and cigarette smoking. These studies suggest that in persons with schizophrenia and schizoaffective disorder, typical antipsychotics may increase basal smoking and decrease people's ability to stop smoking, whereas atypical antipsychotics decrease basal smoking and promote smoking cessation. However, we found that the data available were generally of moderate quality and from small studies, and that there were conflicting findings. The review also critically assesses a number of potential mechanisms for this effect: the use of smoking as a form of self-medication for the side effects of antipsychotics, the effect of antipsychotics on smoking-related cues and the effect of antipsychotics on the appreciation of the economic cost of smoking behaviour. Gaps in the research are noted and recommendations for further study are included. More study of this important issue is needed to clarify the effect of antipsychotics on smoking behaviours.
[show abstract][hide abstract] ABSTRACT: A key underlying process that may contribute to attention-deficit/hyperactivity disorder (ADHD) involves alterations in reward evaluation, including assessing the relative value of immediate over delayed rewards. This study examines whether children with ADHD discount the value of delayed rewards to a greater degree than typically developing children using a delay discounting task.
Children aged 7-9 years diagnosed with ADHD and controls completed a task in which they chose between a hypothetical $10 available after a delay (7, 30, 90 and 180 days) versus various amounts available immediately.
ADHD participants discounted more steeply than controls. However, this effect did not survive covarying of IQ.
ADHD is associated with a steeper delay gradient when contemplating hypothetical later rewards, but not independently of IQ. The interplay of cognitive processing and IQ with reward evaluation in ADHD requires further exploration.
Journal of Child Psychology and Psychiatry 11/2010; 52(3):256-64. · 5.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: The subjective value of a reward (gain) is related to factors such as its size, the delay to its receipt and the probability of its receipt. We examined whether the subjective value of losses was similarly affected by these factors in 128 adults. Participants chose between immediate/certain gains or losses and larger delayed/probabilistic gains or losses. Rewards of $100 were devalued as a function of their delay ("discounted") relatively less than $10 gains while probabilistic $100 rewards were discounted relatively more than $10 rewards. However, there was no effect of outcome size on discounting of delayed or probabilistic losses. For delayed outcomes of each size, the degree to which gains were discounted was positively correlated with the degree to which losses were discounted, whereas for probabilistic outcomes, no such correlation was observed. These results suggest that the processes underlying the subjective valuation of losses are different from those underlying the subjective valuation of gains.