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.SIGNIFICANCE STATEMENT The goal of this study was to determine how temporal delays influence reward preference. We demonstrate that delivering an initially less desirable reward after long delays subsequently increases the consumption and preference for that reward. Furthermore, we identified the basolateral amygdala and the retrosplenial cortex as essential nuclei for mediating the change in reward preference elicited by sunk temporal costs.

Keywords: basolateral amygdala; dopamine; orbitofrontal cortex; preference; retrosplenial cortex; reward.

Figure 1.

Increased preference for the Initial Less Preferred reward delivered after short delays. A, Training schematic for the Different Delay training sessions: Initial Less Preferred after short delays. B, Anticipatory head entries into the food port during the 5 s before reward delivery for the Initial Less Preferred (Short Delay) and Initial Preferred (Long Delay) training sessions. C, Latency to make a head entry into the food port after a reward is delivered for the Initial Less Preferred and Initial Preferred training sessions. D, Preference ratio plotted as the amount of the Initial Less Preferred food consumed out of the total food consumed during preference tests. E, Reward consumption for each flavor during the preference tests. F, Training schematic for the Same Delay training sessions. G, Anticipatory head entries into the food port during the 5 s before reward delivery for the Initial Less Preferred (Medium Delay) and Initial Preferred (Medium Delay) training sessions. H, Latency to make a head entry into food port after a reward is delivered for the Initial Less Preferred and the Initial Preferred training sessions. I, Preference ratio. J, Reward consumption for each flavor during the preference tests. *p < 0.05.

Figure 2.

Increased preference for the Initial Less Preferred reward delivered after long delays. A, Training schematic for the Different Delay training sessions: Initial Less Preferred after long delays. B, Anticipatory head entries into the food port during the 5 s before reward delivery for the Initial Less Preferred (Long Delay) and Initial Preferred (Short Delay) training sessions. C, Latency to make a head entry into the food port after a reward is delivered for the Initial Less Preferred and Initial Preferred training sessions. D, Preference ratio plotted as the amount of the Initial Less Preferred food consumed out of the total food consumed during preference tests. E, Reward consumption for each flavor during the preference tests. F, G, Linear regression relating the change in food consumption as a function of the change in the preference ratio. *p < 0.05.

Figure 3.

The enhanced preference for the Initial Less Preferred reward delivered after long delays does not involve dopamine signaling. A, Training schematic. B, Anticipatory head entries into the food port in rats that received injections of saline or flupenthixol. C, Latency to make a head entry into the food port after a reward is delivered during training sessions in rats that received injections of saline or flupenthixol. D, Preference ratio in rats receiving saline (left) or flupenthixol (right) injections. E, Reward consumption for each flavor during the preference tests in rats receiving saline (left) or flupenthixol (right) injections. F, G, Linear regression relating the change in food consumption as a function of the change in the preference ratio. *p < 0.05. **p < 0.01. ***p < 0.001.

Figure 4.

The OFC is not required for the enhanced preference for the Initial Less Preferred reward delivered after long delays. A, Training schematic. B, Top, The extent of OFC lesions across three coronal planes with the anterior distance from bregma (millimeters) indicated. Bottom, Representative OFC lesion. C, Anticipatory head entries into the food port in sham or OFC-lesioned rats. D, Latency to make a head entry into the food port after a reward is delivered during training sessions in sham or OFC-lesioned rats. E, Preference ratio in sham (left) or OFC-lesioned (right) rats. F, Reward consumption for each flavor during the preference tests in sham (left) or OFC-lesioned (right) rats. G, H, Linear regression relating the change in food consumption as a function of the change in the preference ratio. *p < 0.05. **p < 0.01.

Figure 5.

The BLA is required for the enhanced preference for the Initial Less Preferred reward delivered after long delays. A, Training schematic. B, Top, The extent of BLA lesions across four coronal planes with the anterior distance from bregma (millimeters) indicated. Bottom, Representative BLA lesion. C, Anticipatory head entries into the food port in sham or BLA-lesioned rats. D, Latency to make a head entry into the food port after a reward is delivered during training sessions in sham or BLA-lesioned rats. E, Preference ratio in sham (left) or BLA-lesioned (right) rats. F, Reward consumption for each flavor during the preference tests in sham (left) or BLA-lesioned (right) rats. G, H, Linear regression relating the change in food consumption as a function of the change in the preference ratio. **p < 0.01. ****p < 0.0001.

Figure 6.

The RSC is required for the enhanced preference for the Initial Less Preferred reward delivered after long delays. A, Training schematic. B, Top, The extent of RSC lesions across four coronal planes with the anterior distance from bregma (millimeters) indicated. Bottom, Representative RSC lesion. C, Anticipatory head entries into the food port in sham or RSC-lesioned rats. D, Latency to make a head entry into the food port after a reward is delivered during training sessions in sham or RSC-lesioned rats. E, Preference ratio in sham (left) or RSC-lesioned (right) rats. F, Reward consumption for each flavor during the preference tests in sham (left) or RSC-lesioned (right) rats. G, H, Linear regression relating the change in food consumption as a function of the change in the preference ratio. *p < 0.05. **p < 0.01. ***p < 0.001. ****p < 0.0001.

Figure 7.

Relating the change in preference to the change in the food consumption. A, Change in the preference ratio across all rats that underwent the Different Delay training sessions: Initial Less Preferred after long delays. Color overlays represent a mild increase in preference toward the Initial Preferred reward (orange; change in the preference ratio < 0), a mild increase in preference toward the Initial Less Preferred reward (light blue; change in the preference ratio between 0 and 0.4), and a robust increase in preference toward the Initial Less Preferred reward (dark blue; change in the preference ratio > 0.4). B, Change in the food consumption in rats that displayed a mild increase in preference toward the Initial Preferred reward. C, Change in the food consumption in rats that displayed a mild increase in preference toward the Initial Less Preferred reward. D, Change in the food consumption in rats that displayed a robust increase in preference toward the Initial Less Preferred reward. *p < 0.05, ****p < 0.0001.