2006 |
Scheres, Anouk |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Temporal Discounting of Rewards in Ad/Hd
[unreadable] DESCRIPTION (provided by applicant): The underlying cognitive, motivational, and neural pathways leading to symptoms of Attention Deficit/Hyperactivity Disorder (AD/HD) remain largely unclear. In order to develop optimal treatments for this prevalent disorder, it is crucial to understand the underlying mechanisms associated with it. A promising mechanism proposed to play a crucial role in AD/HD is the mesocortical dopamine system, which has also been suggested to underlie the processing of reward information and motivation. This project will examine reward preferences in an effort to elucidate a possible motivational mechanism underlying AD/HD. Behavioral research with single-choice paradigms has suggested that AD/HD is associated with a tendency to choose small immediate rewards over large delayed ones. However, there is no research thus far in children with AD/HD that examines preferences for small immediate and larger delayed rewards when magnitude of the immediate reward and delay of the large reward vary. By applying a temporal discounting paradigm (temporal discounting refers to the decrease of perceived value as a function of delay) in which magnitudes of immediate rewards and delays of large rewards are varied, this study will examine how reward preferences in children with AD/HD vary as a function of delay and reward magnitude. A second aim is to study the effect of maximum total gain on temporal discounting (TD) in AD/HD. Based on previous research, it may be predicted that if the maximum total amount to be won in a task is high, children with AD/HD may be more inclined to wait for the large reward. The proposed study will formally test this hypothesis. We will use a TD task in which participants will be presented with choices between a smaller immediate reward and a larger delayed reward. The sizes of the immediate and delayed rewards, the delay durations, and the maximum total gain will be varied. We predict that steep TD of large rewards is associated with AD/HD when maximum total gain is relatively small and when the magnitude of the delayed reward is relatively small. We plan to include 36 adolescents with AD/HD, and 36 healthy controls. Participants will be in the age range of 6 - 12, matched for sex and age, and will be required to have an IQ above 70. This research will contribute to a more sophisticated understanding of the role of reward preferences in symptoms of AD/HD. Ultimately, such an understanding will improve treatment strategies for this disorder. [unreadable] [unreadable] [unreadable]
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0.915 |
2007 — 2008 |
Scheres, Anouk |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Fmri of Temporal Reward Discounting in Medication-Naive Adolescents With Adhd
[unreadable] DESCRIPTION (provided by applicant): The underlying neural pathways leading to symptoms of Attention-Deicit/Hyperactivity Disorder (ADHD) remain largely unclear. In order to develop optimal treatments for ADHD, it is crucial to understand the neural mechanisms associated with this disorder. A neural mechanism that may be implicated in ADHD is the "Reward System", a circuitry that originates in the ventral tegmental area and projects to brain structures such as the striatum, nucleus accumbens, limbic areas, and frontal cortex. This mesocorticolimbic dopamine system has been implicated in the processing of reward information and motivation, and has been hypothesized to play a crucial role in ADHD (in particular the striatum). However, this hypothesis has attracted almost no empirical study. The goal of this proposed study is to test this hypothesis by experimentally investigating whether the Brain Reward System is altered in ADHD, and whether such an alteration is related to impulsivity, one of the main symptoms of ADHD. Impulsivity has been operationalized as the preference for small rewards that is immediately available over larger rewards that will be delivered after a period of delay. By examining activation in limbic areas including ventral striatum and frontal areas during temporal discounting of rewards, the proposal for this pilot fMRI study seeks to elucidate a possible neural mechanism underlying symptoms of impulsivity. A secondary goal of this study is to examine alterations in the Brain Reward System as a function of age, and as a function of age by diagnostic group. A temporal discounting task will be used during which participants will be presented with a series of choices between a smaller sooner reward and a larger later reward. We hypothesize that striatal and frontal activation during temporal discounting is altered in ADHD. Furthermore, we hypothesize that there is a correlation between striatal/frontal activation and preference for the immediate reward. In terms of age, we predict that frontal activation during temporal reward discounting will increase with age, and that this effect may differ across diagnostic groups. For this study, we plan to include 24 medication-na[unreadable]ve adolescents with ADHD-combined type, 24 adolescents with ADHD-combined type with a medication history, and 24 healthy controls. Participants will be in the age range of 12 - 17, free of learning disabilities, group-matched for sex and age, and will be required to have an IQ above 70. Addressing the pathophysiology of ADHD in youth is necessary in order to develop improved diagnostic criteria and therapeutic strategies for conditions that have major public health implications. Briefly, ADHD is a very common disorder that incurs great cost to the individual (i.e., poor school achievement, poor peer relationships, increased risk of involvement with criminal justice system, poor occupational attainment, as well as increased risk for substance abuse), the family (poor family relationships, financial and emotional costs of judicial involvement), and society (huge costs of involvement in legal system). [unreadable] [unreadable] [unreadable]
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0.915 |