Failure to delay gratification following septal lesions in rats: Implications for an animal model of disinhibitory psychopathology (original) (raw)

Succumbing to instant gratification without the nucleus accumbens

Animals act to obtain rewards such as food, shelter, and sex. Sometimes, their actions are rewarded or reinforced immediately, but often this is not the case; to be successful, animals must learn to act on the basis of delayed reinforcement. They may also profit by choosing delayed reinforcers over immediate reinforcers, if the delayed reinforcers are sufficiently large. However, individuals differ in their ability to choose delayed rewards.

Striatal and septo-hypothalamic responses to anticipation and outcome of affiliative rewards

Humans are intrinsically motivated to bond with others. The ability to experience affiliative emotions (such as affection/tenderness, sexual attraction, and admiration/awe) may incentivize and promote these affiliative bonds. Here, we interrogate the role of the critical reward circuitry, especially the Nucleus Accumbens (NAcc) and the septo-hypothalamic region, in the anticipation of and response to affiliative rewards using a novel incentive delay task. During Functional Magnetic Resonance Imaging (FMRI), participants (n = 23 healthy humans; 14 female) anticipated and watched videos involving affiliative (tenderness, erotic desire, and awe) and nonaffiliative (i.e ., food) rewards, as well as neutral scenes. On the one hand, anticipation of both affiliative and nonaffiliative rewards increased activity in the NAcc, anterior insula, and supplementary motor cortex, but activity in the amygdala and the ventromedial prefrontal cortex (vmPFC) increased in response to reward outcomes. On the other hand, affiliative rewards more specifically increased activity in the septo-hypothalamic area. Moreover, NAcc activity during anticipation correlated with positive arousal for all rewards, whereas septo-hypothalamic activity during the outcome correlated with positive arousal and motivation for subsequent re-exposure only for affiliative rewards. Together, these findings implicate a general appetitive response in the NAcc to different types of rewards but suggests a more specific response in the septo-hypothalamic region in response to affiliative rewards outcomes. This work also presents a new task for distinguishing between neural responses to affiliative and non-affiliative rewards.

Temporal discounting of aversive consequences in rats

Learning & behavior, 2017

Previous research has extensively evaluated the impact of delay on the value of positive reinforcers, but the study of its impact on the value of aversive consequences is scarce. The present study employed a modification of Evenden and Ryan's procedure (1996, Psychopharmacology, 128(2), 161-170) to obtain data on temporal discounting of an aversive consequence, with rats as experimental subjects. In the first phase of the procedure, rats chose between one-pellet and four-pellet alternatives; when subjects developed preference for the larger-amount alternative, a shock was added to it, resulting in a loss of preference. In the first experimental condition, the delay to shock was progressively increased within each session from zero to 40 s (ascending delays), which resulted in a recovery of the preference for the larger-amount + shock alternative as the delay to shock was increased. In a subsequent condition (descending delays) the delay to shock was progressively decreased withi...