Delays to reward delivery enhance the preference for an initially less desirable option: role for the basolateral amygdala and retrosplenial cortex

Abstract

Temporal costs influence reward-based decisions. This is commonly studied in temporal discounting tasks that involve choosing between cues signaling an imminent reward option or a delayed reward option. However, it is unclear whether the temporal delay before a reward can alter the value of that option. To address this, we identified the relative preference between different flavored rewards during a free-feeding test using male and female rats. Animals underwent training where either the initial preferred or the initial less preferred reward was delivered noncontingently. By manipulating the intertrial interval during training sessions, we could determine whether temporal delays impact reward preference in a subsequent free-feeding test. Rats maintained their initial preference if the same delays were used across all training sessions. When the initial less preferred option was delivered after short delays (high reward rate) and the initial preferred option was delivered after long delays (low reward rate), rats expectedly increased their preference for the initial less desirable option. However, rats also increased their preference for the initial less desirable option under the opposite training contingencies: delivering the initial less preferred reward after long delays and the initial preferred reward after short delays. These data suggest that sunk temporal costs enhance the preference for a less desirable reward option. Pharmacological and lesion experiments were performed to identify the neural systems responsible for this behavioral phenomenon. Our findings demonstrate the basolateral amygdala and retrosplenial cortex are required for temporal delays to enhance the preference for an initially less desirable reward.

Cortico-striatal beta-oscillations as a marker of learned reward value

“…Reward-value was encoded as either a 1s (10μL) or 3s (30μL) period of reward delivery. Previous work suggests reward value is negatively influenced by temporal costs associated with earning a reward (Winstanley et al, 2004b; Kable and Glimcher, 2007; Roesch et al, 2011; Lefner et al, 2021). In the context of this task, the relative value of the low reward choice increased, and the relative value of the high reward choice decreased as the length of the delays and thus the temporal cost of high reward is increased.…”

“…Low-value rewards consisted of 10ul whereas high-value rewards were 30ul (both delivered at a rate of 10 ul/sec). Previous work suggests reward value is negatively influenced by temporal costs associated with earning a reward (19,31,49–51). In the context of this task, the subjective value of the high reward choice decreases as the length of the delay required to obtain reward (temporal cost) increases.…”

Methylphenidate, but not citalopram, decreases impulsive choice in rats performing a temporal discounting task

“…Rats generally maintain their large reward preferences and trial counts across saline control days. Previous research demonstrates that prior associates between rewards and delays do affect future discounting behavior ( 57 ), a problem we avoid by maintaining consistency between sessions. Lastly, IP injections of both methylphenidate and citalopram have effects that last at least 60 min (beyond the length of our sessions) ( 58 , 59 ).…”