Corticolimbic Mechanisms of Behavioral Inhibition under Threat of Punishment

Abstract

Being able to limit the pursuit of reward to prevent negative consequences is an important expression of behavioral inhibition. Everyday examples of an inability to exert such control over behavior are the overconsumption of food and drugs of abuse, which are important factors in the development of obesity and addiction, respectively. Here, we use a behavioral task that assesses the ability of male rats to exert behavioral restraint at the mere sight of palatable food during the presentation of an audiovisual threat cue to investigate the corticolimbic underpinnings of behavioral inhibition. We demonstrate a prominent role for the medial prefrontal cortex in the exertion of control over behavior under threat of punishment. Moreover, task engagement relies on function of the ventral striatum, whereas the basolateral amygdala mediates processing of the threat cue. Together, these data show that inhibition of reward pursuit requires the coordinated action of a network of corticolimbic structures.SIGNIFICANCE STATEMENT There is a need for translational models that allow to dissect mechanisms underlying the processes involved in controlling behavior. In this study, we present a novel behavioral task that assesses the ability of rats to exert behavioral restraint over the consumption of a visually present sucrose pellet during the presentation of an audiovisual threat cue. This task requires relatively little behavioral training and it discerns distinct behavioral impairments, including a failure to retrieve stimulus value, a reduced task engagement, and compromised inhibition of behavior. Using pharmacological inactivations of different regions of the corticolimbic system of the rat, we demonstrate dissociable roles for the prefrontal cortex, amygdala, and striatum in inhibition of reward pursuit under threat of punishment.

Keywords: corticolimbic; inhibition; punishment; reward.

Figure 1.

Task description. a, Behavioral setup. The task comprised 60 trials in which a sucrose pellet was delivered into a food port. In half of the trials, animals could take the pellet directly without any negative consequences (no-stimulus trials). In the other half of the trials, pellet delivery was accompanied by a 12 s audiovisual stimulus that signaled to the animals that they had to wait with entering the food port until stimulus termination (stimulus trials). Food port entry during the stimulus was detected by an infrared movement detector and was punished with a 0.3 s electric foot shock. Inset shows the individual animals' foot shock intensities (median ± 25–75th percentile, whiskers extend to minimum and maximum values). For training data and latencies per trial type, see Figure 1-1, and Figure 1-2. b, Possible phenotypes after (neural) manipulation. Note that for no-stimulus trials, both options (Reward taken and Omitted) add up to 100%, as well as for the options during the stimulus trials (Reward taken − Success, Reward taken − Shock, Omitted). Dark arrows under graphs represent possible changes in latency of pellet retrieval for each trial type. For behavioral data of the reduced task engagement phenotype, see Figure 1-3. For statistics, see Figure 1-4. c, Quantification of a trial from Movie 2, demonstrating attract and repel behavior directed toward and away from the food receptacle during a stimulus trial.

Figure 2.

Effects of pharmacological inactivation of the medial PFC on task behavior. a, Effects of prelimbic cortex inactivation. No-stimulus trials, reward taken: paired t test, t₍₁₁₎ = 1.1, p = 0.30; latency: t₍₁₁₎ = 0.6, p = 0.55. Stimulus trials, number of success trials: t₍₁₁₎ = 3.2, p = 0.0079, latency of success trials: t₍₁₁₎ = 0.5, p = 0.66; number of shock trials: t₍₁₁₎ = 4.2, p = 0.0015, latency of shock trials: t₍₁₁₎ = 0.8, p = 0.42; number of omissions: t₍₁₁₎ = 1.0, p = 0.35; Shock index: t₍₁₁₎ = 4.5, p = 0.0008. b, Effects of infralimbic cortex inactivation. No-stimulus trials, reward taken: paired t test, t₍₈₎ = 1.7, p = 0.12; latency: t₍₈₎ = 0.2, p = 0.83. Stimulus trials, number of success trials: t₍₈₎ = 2.6, p = 0.0293, latency of success trials: t₍₈₎ = 0.7, p = 0.51; number of shock trials: t₍₈₎ = 4.5, p = 0.0021, latency of shock trials: t₍₈₎ = 1.8, p = 0.11; number of omissions: t₍₈₎ = 2.0, p = 0.084. Shock index: t₍₈₎ = 5.8, p = 0.0004. c, Effects of medial orbitofrontal cortex inactivation. No-stimulus trials, reward taken: paired t test, t₍₈₎ = 0.5, p = 0.61; latency: t₍₈₎ = 0.1, p = 0.94. Stimulus trials, number of success trials: t₍₈₎ = 2.0, p = 0.0840, latency of success trials: t₍₈₎ = 0.8, p = 0.47; number of shock trials: t₍₈₎ = 2.5, p = 0.0348, latency of shock trials: t₍₈₎ = 2.5, p = 0.0360; number of omissions: t₍₈₎ = 0.6, p = 0.59. Shock index: t₍₈₎ = 0.3, p = 0.0316. d, Effects of anterior cingulate cortex inactivation. No-stimulus trials, reward taken: paired t test, t₍₉₎ = 0.5, p = 0.66; latency: t₍₉₎ = 0.3, p = 0.0262. Stimulus trials, number of success trials: t₍₉₎ = 2.7, p = 0.0235, latency of success trials: t₍₉₎ = 0.1, p = 0.23; number of shock trials: t₍₉₎ = 3.2, p = 0.0114, latency of shock trials: t₍₉₎ = 0.2, p = 0.88; number of omissions: t₍₉₎ = 0.6, p = 0.56. Shock index: t₍₉₎ = 0.3, p = 0.0085. The shock index is the number of shock trials as a fraction of the stimulus trials in which reward was taken. Red crosses in the coronal brain sections represent the infusion sites in each experiment. Gray lines in shock index graphs indicate individual animals. For latency analyses, the median latency per animal per trial type was used. Latency in success trials represents the latency to pellet retrieval after stimulus offset; in other trials the latencies represent the latency of pellet retrieval after reward delivery. *p < 0.05, **p < 0.01, ***p < 0.001 in paired t test (for statistical table, see Figure 1-4).

Figure 3.

Effects of pharmacological inactivation of the lateral orbitofrontal cortex and basolateral amygdala on task behavior. a, Effects of lateral orbitofrontal cortex inactivation. No-stimulus trials, reward taken: paired t test, t₍₈₎ = 3.1, p = 0.0157; latency: t₍₇₎ = 0.3, p = 0.0286. Stimulus trials, number of success trials: t₍₈₎ = 4.8, p = 0.0014, latency of success trials: t₍₈₎ = 3.4, p = 0.0091; number of shock trials: t₍₈₎ = 1.0, p = 0.35, latency of shock trials: t₍₇₎ = 0.01, p = 0.99; number of omissions: t₍₈₎ = 0.4, p = 0.0050. Shock index: t₍₈₎ = 2.8, p = 0.0235. b, Effects of basolateral amygdala inactivation. No-stimulus trials, reward taken: paired t test, t₍₉₎ = 0.6, p = 0.53); latency: t₍₉₎ = 1.6, p = 0.14. Stimulus trials, number of success trials: t₍₉₎ = 21.2, p < 0.0001, latency of success trials: t₍₇₎ = 2.7, p = 0.0317; number of shock trials: t₍₉₎ = 8.0, p < 0.0001, latency of shock trials: t₍₉₎ = 8.3, p < 0.0001; number of omissions: t₍₉₎ = 0.8, p = 0.46. Shock index: t₍₉₎ = 19.3, p < 0.0001. For an additional latency analysis of this experiment, see Figure 3-1. The shock index is the number of shock trials as a fraction of the stimulus trials in which reward was taken. Red crosses in the coronal brain sections represent the infusion sites in each experiment. Gray lines in shock index graphs indicate individual animals. Latency in success trials represents the latency to pellet retrieval after stimulus offset; in other trials the latencies represent the latency of pellet retrieval after reward delivery. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 in paired t test (for statistical table, see Figure 1-4).

Figure 4.

Effects of pharmacological inactivation of striatal subregions on task behavior. a, Effects of ventral striatum inactivation. No-stimulus trials, reward taken: paired t test, t₍₁₆₎ = 3.9, p = 0.0013); latency: t₍₁₄₎ = 1.1, p = 0.28. Stimulus trials, number of success trials: t₍₁₆₎ = 5.5, p < 0.0001, latency of success trials: t₍₁₁₎ = 2.1, p = 0.064; number of shock trials: t₍₁₆₎ = 1.1, p = 0.28, latency of shock trials: t₍₁₂₎ = 1.2, p = 0.24; number of omissions: t₍₁₆₎ = 3.7, p = 0.0020. Shock index: t₍₁₄₎ = 4.0, p = 0.0014. For the animals for which the cannulas ended up exclusively in the nucleus accumbens shell, see Figure 4-1. b, Effects of dorsomedial striatum inactivation. No-stimulus trials, reward taken: paired t test, t₍₇₎ = 2.3, p = 0.056; latency: t₍₅₎ = 1.2, p = 0.30. Stimulus trials, number of success trials: t₍₇₎ = 2.6, p = 0.0337, latency of success trials: t₍₅₎ = 2.6, p = 0.0462; number of shock trials: t₍₇₎ = 0.4, p = 0.67, latency of shock trials: t₍₅₎ = 1.3, p = 0.26; number of omissions: t₍₇₎ = 2.5, p = 0.0421. Shock index: t₍₇₎ = 1.5, p = 0.21. c, Effects of dorsolateral striatum inactivation. No-stimulus trials, reward taken: paired t test, t₍₁₀₎ = 1.3, p = 0.22; latency: t₍₁₀₎ = 1.7, p = 0.13. Stimulus trials, number of success trials: t₍₁₀₎ = 2.1, p = 0.057, latency of success trials: t₍₉₎ = 1.9, p = 0.095; number of shock trials: t₍₁₀₎ = 1.8, p = 0.10, latency of shock trials: t₍₁₀₎ = 1.3, p = 0.22; number of omissions: t₍₁₀₎ = 0.9, p = 0.38. Shock index: t₍₁₀₎ = 2.2, p = 0.0486. The shock index is the number of shock trials as a fraction of the stimulus trials in which reward was taken. Red crosses in the coronal brain sections represent the infusion sites in each experiment. Gray lines in shock index graphs indicate individual animals. Latency in success trials represents the latency to pellet retrieval after stimulus offset; in other trials the latencies represent the latency of pellet retrieval after reward delivery. ****p < 0.0001, ***p < 0.001, **p < 0.01, *p < 0.05, #p < 0.1 in paired t test (for statistical table, see Figure 1-4).

Figure 5.

Control experiments. a, Effects of pharmacological inactivation of the olfactory cortex on task behavior. No-stimulus trials, reward taken: paired t test, t₍₈₎ = 1.4, p = 0.21; latency: t₍₈₎ = 0.2, p = 0.83. Stimulus trials, number of success trials: t₍₈₎ = 1.8, p = 0.12, latency of success trials: t₍₈₎ = 0.1, p = 0.95; number of shock trials: t₍₈₎ = 1.3, p = 0.25, latency of shock trials: t₍₈₎ = 2.1, p = 0.066; number of omissions: t₍₈₎ = 1.3, p = 0.25. Shock index: t₍₈₎ = 1.3, p = 0.23. b, Pharmacological inactivations did not the change latency to tail withdrawal in a tail withdrawal test (n = 59 rats, two-way repeated-measures ANOVA, no main effect of infusion: F_(1,53) = 0.33, p = 0.57; or infusion × group interaction effect: F_(5,53) = 1.29, p = 0.28). c, Pharmacological inactivations did not change chow intake in a free-feeding assay (two-way repeated-measures ANOVA, no main effect of infusion: n = 59 rats, F_(1,53) = 0.35, p = 0.55; or infusion × group interaction effect: F_(5,53) = 1.02, p = 0.41). For statistical table, see Figure 1-4. PrL, prelimbic cortex; IL, infralimbic cortex; mOFC, medial orbitofrontal cortex; lOFC, lateral orbitofrontal cortex; ACC, anterior cingulate cortex; BLA, basolateral amygdala.