Stimulation in the Rat Anterior Insula and Anterior Cingulate During an Effortful Weightlifting Task

Non-angry aggressive arousal and angriffsberietschaft: A narrative review of the phenomenology and physiology of proactive/offensive aggression motivation and escalation in people and other animals

Human aggression typologies largely correspond with those for other animals. While there may be no non-human equivalent of angry reactive aggression, we propose that human proactive aggression is similar to offense in other animals' dominance contests for territory or social status. Like predation/hunting, but unlike defense, offense and proactive aggression are positively reinforcing, involving dopamine release in accumbens. The drive these motivational states provide must suffice to overcome fear associated with initiating risky fights. We term the neural activity motivating proactive aggression "non-angry aggressive arousal", but use "angriffsberietschaft" for offense motivation in other animals to acknowledge possible differences. Temporal variation in angriffsberietschaft partitions fights into bouts; engendering reduced anti-predator vigilance, redirected aggression and motivational over-ride. Increased aggressive arousal drives threat-to-attack transitions, as in verbal-to-physical escalation and beyond that, into hyper-aggression. Proactive aggression and offense involve related neural activity states. Cingulate, insular and prefrontal cortices energize/modulate aggression through a subcortical core containing subnuclei for each aggression type. These proposals will deepen understanding of aggression across taxa, guiding prevention/intervention for human violence.

An orbitofrontal cortex-anterior insular cortex circuit gates compulsive cocaine use

Compulsive drug use, a cardinal symptom of drug addiction, is characterized by persistent substance use despite adverse consequences. However, little is known about the neural circuit mechanisms behind this behavior. Using a footshock-punished cocaine self-administration procedure, we found individual variability of rats in the process of drug addiction, and rats with compulsive cocaine use presented increased neural activity of the anterior insular cortex (aIC) compared with noncompulsive rats. Chemogenetic manipulating activity of aIC neurons, especially aIC glutamatergic neurons, bidirectionally regulated compulsive cocaine intake. Furthermore, the aIC received inputs from the orbitofrontal cortex (OFC), and the OFC-aIC circuit was enhanced in rats with compulsive cocaine use. Suppression of the OFC-aIC circuit switched rats from punishment resistance to sensitivity, while potentiation of this circuit increased compulsive cocaine use. In conclusion, our results found that aIC glutamatergic neurons and the OFC-aIC circuit gated the shift from controlled to compulsive cocaine use, which could serve as potential therapeutic targets for drug addiction.

Dorsomedial prefrontal neural ensembles reflect changes in task utility that culminate in task quitting

When performing a physically demanding behavior, sometimes the optimal choice is to quit the behavior rather than persist to minimize energy expenditure for the benefits gained. The dorsomedial prefrontal cortex (dmPFC), consisting of the anterior cingulate cortex and secondary motor area, likely contributes toward such utility assessments. Here, we examined how male rat dmPFC single unit and ensemble-level activity corresponded to changes in task utility and quitting in an effortful weight lifting task. Rats carried out two task paradigms: one that became progressively more physically demanding over time and a second fixed effort version. Rats could quit the task at any time. Dorsomedial PFC neurons were highly responsive to each behavioral stage of the task, consisting of rope pulling, reward retrieval, and reward area leaving. Activity was highest early in sessions, commensurate with the highest relative task utility, then decreased until the point of quitting. Neural ensembles consistently represented the sequential behavioral phases of the task. However, these representations were modified over time and became more distinct over the course of the session. These results suggest that dmPFC neurons represent behavioral states that are dynamically modified as behaviors lose their utility, culminating in task quitting.NEW & NOTEWORTHY When carrying out a physically demanding task, animals must continually assess whether to persist or quit. In this study, we recorded neurons in the dorsomedial prefrontal cortex (dmPFC) of rats as they carried out a challenging weightlifting task, up to the point of quitting. We demonstrate that dmPFC neurons form a representation of the task that is modified, via a decrease in firing rate, by the decreasing the utility of the task that may signal quitting.