Medial Prefrontal Cortex Predicts Intertemporal Choice

People often make shortsighted decisions to receive small benefits in the present rather than large benefits in the future, that is, to favor their current selves over their future selves. In two studies using fMRI, we demonstrated that people make such decisions in part because they fail to engage in the same degree of self-referential processing when thinking about their future selves. When participants predicted how much they would enjoy an event in the future, they showed less activity in brain regions associated with introspective self-reference—such as the ventromedial pFC (vMPFC)—than when they predicted how much they would enjoy events in the present. Moreover, the magnitude of vMPFC reduction predicted the extent to which participants made shortsighted monetary decisions several weeks later. In light of recent findings that the vMPFC contributes to the ability to simulate future events from a first-person perspective, these data suggest that shortsighted decisions result in part from a failure to fully imagine the subjective experience of one's future self.Psycholog

Impulsivity and self-control during intertemporal decision making linked to the neural dynamics of reward value representation

A characteristic marker of impulsive decision making is the discounting of delayed rewards, demonstrated via choice preferences and choice-related brain activity. However, delay discounting may also arise from how subjective reward value is dynamically represented in the brain when anticipating an upcoming chosen reward. In the current study, brain activity was continuously monitored as human participants freely selected an immediate or delayed primary liquid reward and then waited for the specified delay before consuming it. The ventromedial prefrontal cortex (vmPFC) exhibited a characteristic pattern of activity dynamics during the delay period, as well as modulation during choice, that is consistent with the time-discounted coding of subjective value. The ventral striatum (VS) exhibited a similar activity pattern, but preferentially in impulsive individuals. A contrasting profile of delay-related and choice activation was observed in the anterior PFC (aPFC), but selectively in patient individuals. Functional connectivity analyses indicated that both vmPFC and aPFC exerted modulatory, but opposite, influences on VS activation. These results link behavioral impulsivity and self-control to dynamically evolving neural representations of future reward value, not just during choice, but also during postchoice delay periods

The Neural Representation of Value and individual Differences in Human Intertemporal Choice

Intertemporal choices, or decisions that involve tradeoffs between rewards and time, are ubiquitous in our daily lives. The tendency to devalue, or discount, future rewards has been linked to maladaptive long-term health and financial outcomes. Despite their broad clinical relevance, individual differences in discounting preferences are poorly understood. In this thesis, we make progress on the understanding of the neural basis of these decisions and factors that affect individual differences. The first two chapters focus on neurobiology. Chapter 2 investigates the decision-related variables that best explain the observed patterns of BOLD activity in ventromedial prefrontal cortex (VMPFC) and ventral striatum (VS) during intertemporal choice. We find that these regions carry different signals and likely contribute to different stages of the choice process. Across the brain, we find four kinds of value-responsive regions, each carrying different combinations of value-related signals. Next, we examine whether we can predict participants\u27 choices from any or all of these groups of regions, and find that we can predict choice from most value-responsive regions, with interesting exceptions. In Chapter 3, we identify a novel brain predictor of individual differences in discounting. When participants are making judgments about how far away some number of days feels, discount rates, measured a week later, can be predicted from how VMPFC and VS respond as a function of temporal distance. This difference in the basic response to delayed time intervals could be a target for interventions aiming to reduce discount rates. In the final chapter, we find several behavioral manipulations that are able to reduce discount rates persistently and to a significant degree. We find that there is a general lack of knowledge about the normative strategy in the monetary discounting task, and that providing information about this strategy - to accept all delayed offers that provide higher interest rates than one could obtain elsewhere - reduces discounting significantly, for at least one month. Information about peers\u27 strategies for making these decisions also reduces discounting. Taken together, this work advances our understanding of individual differences in discounting and further suggests interventions that could be used to reduce discounting

The neural correlates of intertemporal decision‐making: Contributions of subjective value, stimulus type, and trait impulsivity

Making choices between payoffs available at different points in time reliably engages a decision‐making brain circuit that includes medial prefrontal cortex (mPFC), posterior cingulate cortex (PCC), and ventral striatum (VS). Previous neuroimaging studies produced differing accounts of the functions of these regions, including that these regions: (1) are sensitive to the value of rewards discounted by a function of delay ('subjective value'); (2) are differentially sensitive to the availability of an immediate reward; and (3) are implicated in impulsive decision‐making. In this event‐related fMRI study of 20 volunteers, these hypotheses were investigated simultaneously using a delay discounting task in which magnitude of rewards and stimulus type, i.e., the presence or absence of an immediate option, were independently varied, and in which participants' trait impulsivity was assessed with the Barratt Impulsiveness Scale. Results showed that mPFC, PCC, and VS are sensitive to the subjective value of rewards, whereas mPFC and PCC, but not VS, are sensitive to the presence of an immediate reward in the choice option. Moderation by individual differences in trait impulsivity was specific to the mPFC. Conjunction analysis showed significant overlap in mPFC and PCC for the main effects of subjective value and stimulus type, indicating these regions may serve multiple distinct roles during intertemporal decision‐making. These findings significantly advance our understanding of the specificity and overlap of functions subserved by different regions involved in intertemporal decision‐making, and help to reconcile conflicting accounts in the literature. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86833/1/21136_ftp.pd

Neural Systems Underlying Individual Differences in Intertemporal Decision-making

Excessively choosing immediate over larger future rewards, or delay discounting (DD), associates with multiple clinical conditions. Individual differences in DD likely depend on variations in the activation of and functional interactions between networks, representing possible endophenotypes for associated disorders, including alcohol use disorders (AUDs). Numerous fMRI studies have probed the neural bases of DD, but investigations of large-scale networks remains scant. We addressed this gap by testing whether activation within large-scale networks during “Now/Later” decision-making predicts individual differences in DD. To do so, we scanned 95 social drinkers (18–40 years; 50 females) using fMRI during hypothetical choices between small monetary amounts available “today” or larger amounts available later. We identified neural networks engaged during Now/Later choice using independent component analysis (ICA) and tested the relationship between component activation and degree of DD. The activity of two components during Now/Later choice correlated with individual DD rates: a temporal lobe network positively correlated with DD, while a frontoparietal-striatal network negatively correlated with DD. Activation differences between these networks predicted individual differences in DD and their negative correlation during Now/Later choice suggests functional competition. A generalized psychophysiological interactions (gPPI) analysis confirmed a decrease in their functional connectivity during decision-making. The functional connectivity of these two networks negatively correlates with alcohol-related harm, potentially implicating these networks in AUDs. These findings provide novel insight into the neural underpinnings of individual differences in impulsive decision making with potential implications for addiction and related disorders in which impulsivity is a defining feature

Time for a Change? Brain Activity and Behavioral Performance Reveal Different Dynamics at Short, Intermediate, and Long Delay Intervals During a Delay Discounting Task

In our day to day lives, the ability to make goal-oriented decisions plays a crucial role in both our work and social lives. Therefore, researchers have examined how factors such as a varying reward or delay may affect decision making. One’s performance when making intertemporal choices, decisions made between a smaller and sooner (SS) reward and a larger and later (LL) reward, are often examined to study these factors. Although time and reward magnitude are important dimensions when individuals make decisions during delay discounting, little is known about the relationship between time perception, reward magnitude, and underlying neural mechanisms. To address this gap in literature, participants completed a modified delay discounting task during fMRI with stimuli that included fluctuating reward and delay values. An exploratory factor analysis using behavioral data identified three categories of delays and reward values that were used to create brain contrasts. In these comparisons, the middle frontal gyrus and cingulate gyrus seemed to be more involved when choosing rewards of greater magnitude while the medial frontal gyrus and insula were found to be more active for longer delays. Our results suggest that delay and reward determination are handled by separate neural networks

Event-related Potentials reveal differential Brain Regions implicated in Discounting in Two Tasks

The way people make decisions about future benefits – termed discounting - has important implications for both financial planning and health behaviour. Several theories assume that, when delaying gratification, the lower weight given to future benefits (the discount rate) declines exponentially. However there is considerable evidence that it declines hyperbolically with the rate of discount being proportionate to the delay distance. There is relatively little evidence as to whether neural areas mediating time- dependent discounting processes differ according to the nature of the task. The present study investigates the potential neurological mechanisms underpinning domain-specific discounting processes. We present high-density event-related potentials (ERPs) data from a task in which participants were asked to make decisions about financial rewards or their health over short and long time-horizons. Participants (n=17) made a button-press response to their preference for an immediate or delayed gain (in the case of finance) or loss (in the case of health), with the discrepancy in the size of benefits/losses varying between alternatives. Waveform components elicited during the task were similar for both domains and included posterior N1, frontal P2 and posterior P3 components. We provide source dipole evidence that differential brain activation does occur across domains with results suggesting the possible involvement of the right cingulate gyrus and left claustrum for the health domain and the left medial and right superior frontal gyri for the finance domain. However, little evidence for differential activation across time horizons is found.Decision Making, Domain-Specific Discounting, Event-Related Potentials

Event-Related Potentials Reveal Differential Brain Regions Implicated in Discounting in Two Tasks

The way people make decisions about future benefits termed discounting - has important implications for both financial planning and health behaviour. Several theories assume that, when delaying gratification, the lower weight given to future benefits (the discount rate) declines exponentially. However there is considerable evidence that it declines hyperbolically with the rate of discount being proportionate to the delay distance. There is relatively little evidence as to whether neural areas mediating timedependent discounting processes differ according to the nature of the task. The present study investigates the potential neurological mechanisms underpinning domain-specific discounting processes. We present high-density event-related potentials (ERPs) data from a task in which participants were asked to make decisions about financial rewards or their health over short and long time-horizons. Participants (n=17) made a button-press response to their preference for an immediate or delayed gain (in the case of finance) or loss (in the case of health), with the discrepancy in the size of benefits/losses varying between alternatives. Waveform components elicited during the task were similar for both domains and included posterior N1, frontal P2 and posterior P3 components. We provide source dipole evidence that differential brain activation does occur across domains with results suggesting the possible involvement of the right cingulate gyrus and left claustrum for the health domain and the left medial and right superior frontal gyri for the finance domain. However, little evidence for differential activation across time horizons is found.

Neural Markers of Individual Differences in Decision-making

In the last few years, neuroscientists have begun to identify associations between individual differences in decision-making and features of neuroanatomy and neurophysiology. Different tendencies in decision making, such as tolerance for risk, delay or effort, have been linked to various neurobiological measures, such as morphometry, structural connectivity, functional connectivity or the function of neurotransmitter systems. Though far from immutable, these neural features may nonetheless be suitable as relatively stable biomarkers for different decision traits. The establishment of such markers would achieve one of the stated goals of neuroeconomics, which is to improve the prediction of economic behavior across different contexts

Intrinsic prefrontal organization underlies associations between achievement motivation and delay discounting

Achievement motivation is a core component of human decision making. However, neural mechanisms that link achievement motivation and intertemporal choice have not yet been elucidated. Here, we examined neural pathways underlying the relationship between achievement motivation and intertemporal choice using a delay discounting task and resting-state functional magnetic resonance imaging on 86 healthy subjects. Behaviorally, delay discounting rate was positively correlated with achievement motivation. Functional coupling of the dorsolateral prefrontal cortex (dlPFC) with the medial prefrontal cortex (mPFC), medial orbitofrontal cortex and ventral striatum was positively correlated with achievement motivation. Notably, the mediation analysis showed that the impact of achievement motivation on delay discounting was mediated by intrinsic connectivity between the dlPFC and mPFC. Our findings suggest that intrinsic organization within the prefrontal cortex plays a key role in linking achievement motivation and intertemporal choice