Previous experience with delays affects delay discounting in animal model of ADHD

Abstract

Background ADHD is a disorder where a common symptom is impulsive behaviour, a broad term associated with making sub-optimal choices. One frequently used method to investigate impulsive behaviour is delay discounting, which involves choosing between a small, immediate reinforcer and a delayed, larger one. Choosing the small immediate reinforcer is by itself, however, not sufficient for terming the choice impulsive, as all organisms eventually switch to choosing the small, immediate reinforcer when the delay to the larger reinforcer becomes long. This switch can be termed impulsive only when it occurs more frequently, or at shorter LL delays, than typically observed in normal controls. A poorly understood aspect is how choice is influenced by previous experience with delays. Using an animal model of Attention-Deficit/Hyperactivity Disorder, the Spontaneously Hypertensive Rat, we manipulated the order of exposure to delays in a delay discounting task. Following a preference test, the Ascending group experienced gradually increasing delays between choice and reinforcer while the Descending group were exposed to these delays in reverse order. Results The results showed that the Descending group chose the small, immediate reinforcer over the larger delayed to a much larger extent than the Ascending group, and continued to do so even when the delay component was ultimately removed. Strain effects were found in the Ascending group, with SHRs switching to the small, immediate reinforcer earlier than controls as the delay to the larger reinforcer increased. Conclusion The data suggests that delay discounting is affected by history of exposure to delayed consequences. When reinforcement contingencies are incrementally changed from having no response-reinforcer delay to a long delay, discounting of delayed consequences is gradual. However, a sudden change from no delay to a long delay, without intermediate training, results in a rapid switch to the small, immediate reinforcer option, and this behaviour is somewhat resilient to the shortening and eventual removal of the large reinforcer delay. The implication is that attempting to reduce already existing impulsive behaviour in children with ADHD will require gradual habituation and not sudden changes in reinforcement contingencies.

Choice impulsivity after repeated social stress is associated with increased perineuronal nets in the medial prefrontal cortex

“…Based on these studies and our current work, we hypothesize that females will show higher choice impulsivity and PNNs densities in the mPFC compared to males after ISD. Second, previous work has shown that increases in delay discounting behavior depend on the order in which delays are presented and/or reward-related cues 29 , 54 , 66 , 67 . Regarding delay presentation, some studies have shown that the administration of amphetamine increases or decreases discounting behavior depending on the order of delay presentation 54 , 66 , and suggest that the effects of amphetamine reflect perseveration and not intertemporal decision-making deficits.…”

“…Second, previous work has shown that increases in delay discounting behavior depend on the order in which delays are presented and/or reward-related cues 29 , 54 , 66 , 67 . Regarding delay presentation, some studies have shown that the administration of amphetamine increases or decreases discounting behavior depending on the order of delay presentation 54 , 66 , and suggest that the effects of amphetamine reflect perseveration and not intertemporal decision-making deficits. Our results show that ISD increases discounting with increasing delays, which is the opposite of what was expected to be found if stressed animals persevere with a given response.…”

Timing and delay discounting in attention‐deficit/hyperactivity disorder: A translational approach

“…Given the differences between strains in the timing task from Experiment 1, we predicted that we would observe differences in the delay-discounting task where response consequences are distributed in time, and thus, temporal processing may play a critical role. There has been a fairly substantial amount of work assessing impulsive choice in SHR/NCrl rats using a delay-discounting paradigm, and most of that work has found SHR/NCrl rats to be more impulsive than controls (Aparicio et al, 2019(Aparicio et al, , 2020Bizot et al, 2007;Fox et al, 2008;Hand et al, 2009;Orduña, 2015;Orduña & Mercado, 2017;Sanabria & Killeen, 2008;Sjoberg et al, 2023;Sutherland et al, 2009;Wooters & Bardo, 2011); however, very little work has included an outbred control strain like the WI strain. This is particularly important given the probable inadequacies of the WKY/NCrl strain to serve as a control for SHR/NCrl (Alsop, 2007;Sagvolden et al, 2009), and some mixed findings when SHR/NCrl and WKY/NCrl are compared (Adriani et al, 2003;Garcia & Kirkpatrick, 2013;González-Barriga & Orduña, 2022).…”

Differential processing of delay versus uncertainty in male but not female 16p11.2 hemideletion mice

“…We had mice first undergo “Worsening” and then “Improving” versions of delay and probability discounting because the acclimation to an Improving schedule (i.e. going from no delay training to large delay testing) can obscure sensitivity to delay in models of neurodevelopmental disorders (Sjoberg et al, 2023).…”

“…We had mice first undergo "Worsening" and then "Improving" versions of delay and probability discounting because the acclimation to an Improving schedule (i.e. going from no delay training to large delay testing) can obscure sensitivity to delay in models of neurodevelopmental disorders (Sjoberg et al, 2023). Each schedule promotes a different choice pattern, which gives us the ability to compare whether delay or risk orientation alters choice in 16p11.2 hemideletion mice.…”