Delay discounting without decision-making: medial prefrontal cortex and amygdala activations reflect immediacy processing and correlate with impulsivity and anxious-depressive traits

Abstract

Humans value rewards less when these are delivered in the future as opposed to immediately, a phenomenon referred to as delay discounting. While delay discounting has been studied during the anticipation of rewards and in the context of intertemporal decision-making, little is known about its neural correlates in the outcome phase (during reward delivery) and their relation to personality. Personality traits that have been associated with increased delay discounting include impulsivity and, potentially, anxious-depressive traits. Here we performed functional magnetic resonance imaging (fMRI) in 72 healthy participants while they carried out a monetary incentive delay (MID) task with a delay manipulation. In sixty percent of the experimental trials, participants won rewards that differed in magnitude (0.05€, 0.50€ or 1€) and delay until delivery (immediately, 10 days, or 100 days). A factor analysis on questionnaires yielded two factors reflecting Impulsivity and Anxiety/Depression, which we used to examine potential relationships between personality and delay discounting. When winning a reward, medial prefrontal cortex (mPFC) activation was higher for immediate compared to delayed rewards. Moreover, amygdala activation correlated with reward magnitude for immediate but not for delayed rewards. Amygdala activation to winning immediate rewards was higher in more impulsive participants, while mPFC activation to winning immediate rewards was higher in more anxious-depressed participants. Our results uncover neural correlates of delay discounting during reward delivery, and suggest that impulsivity and subclinical anxious-depressive traits are related to stronger neural responses for winning immediate relative to delayed rewards.

Transcranial direct current stimulation (tDCS) over vmPFC modulates interactions between reward and emotion in delay discounting

“…This finding supports models suggesting that the vmPFC is the key node involved in “hot” decision-making processes and preferentially influenced by physiological modifications, such as those sensed during emotion processing 44 . Facing an emotional and impulsive trial, stimulation of the vmPFC may have modulated activity in the amygdala, a structure known for exhibiting greater activity when immediate rewards are preferred 40,41 and when processing emotions 79–81 . Delay discounting in the emotional trials may have therefore relied more heavily on limbic structures such as the amygdala therefore hampering the effect of vmPFC stimulation on average delay discounting.…”

“…Amygdala damage or disconnection between vmPFC and the amygdala impairs performance on delay discounting tasks in rodents 29–31 and contributes to deficits on different decision-making tasks in humans 32–37 . The amygdala is also sensitive to the magnitude effect - a well-known effect described as greater discounting of low-magnitude compared to high-magnitude rewards 2,38,39 - and shows greater activity when immediate rewards are preferred 40,41 .…”

Anhedonia in Trauma-Exposed Individuals: Functional Connectivity and Decision-Making Correlates

“…While Lempert & Pizzagalli (36) found that decreased DD was associated with anhedonia in healthy individuals, increased DD has been more frequently associated with increased vulnerability to psychopathology (37). The literature on DD in internalizing disorders is mixed, with reports of increased, decreased, or unchanged DD in individuals with high trait anxiety (38–40), and social anxiety (41, 42), but increased DD in MDD (43–45). It is possible that inconsistent findings of increased versus decreased DD in internalizing disorders may relate to the presence or absence of significant anhedonia in the included samples, a feature that is not typically assessed or characterized.…”

Impaired Decision Making and Loss of Inhibitory-Control in a Rat Model of Huntington Disease

“…In healthy humans, a high level of impulsivity in a delay discounting task (DD) was associated with higher amygdala activation for winning immediate rewards (Ludwig et al, 2015). Moreover, trait impulsivity was positively correlated with the level of activity in response to reward cues in the anterior cingulate cortex (ACC) and amygdala (Kerr et al, 2015).…”