Effort-related functions of nucleus accumbens dopamine and associated forebrain circuits

Background Over the last several years, it has become apparent that there are critical problems with the hypothesis that brain dopamine (DA) systems, particularly in the nucleus accumbens, directly mediate the rewarding or primary motivational characteristics of natural stimuli such as food. Hypotheses related to DA function are undergoing a substantial restructuring, such that the classic emphasis on hedonia and primary reward is giving way to diverse lines of research that focus on aspects of instrumental learning, reward prediction, incentive motivation, and behavioral activation. Objective The present review discusses dopaminergic involvement in behavioral activation and, in particular, emphasizes the effort-related functions of nucleus accumbens DA and associated forebrain circuitry. Results The effects of accumbens DA depletions on food-seeking behavior are critically dependent upon the work requirements of the task. Lever pressing schedules that have minimal work requirements are largely unaffected by accumbens DA depletions, whereas reinforcement schedules that have high work (e.g., ratio) requirements are substantially impaired by accumbens DA depletions. Moreover, interference with accumbens DA transmission exerts a powerful influence over effort-related decision making. Rats with accumbens DA depletions reallocate their instrumental behavior away from food-reinforced tasks that have high response requirements, and instead, these rats select a less-effortful type of food-seeking behavior. Conclusions Along with prefrontal cortex and the amygdala, nucleus accumbens is a component of the brain circuitry regulating effort-related functions. Studies of the brain systems regulating effort-based processes may have implications for understanding drug abuse, as well as energy-related disorders such as psychomotor slowing, fatigue, or anergia in depression

Non-suicidal Self-Injury and Firesetting: Shared and Unique Correlates Among School-Based Adolescents

Distinct behaviors such as non-suicidal self-injury (NSSI) and firesetting may represent functionally equivalent attempts to regulate difficult affective/cognitive or social experiences during adolescence. This study examined possible mechanisms leading to NSSI, as opposed to firesetting, as well as co-occurrence of these behaviors. Participants aged 12–18 years (N = 2,356; 67.5 % female) completed self-report questionnaires measuring NSSI and firesetting, as well as socio-demographic and psychosocial factors including personality traits related to impulsivity and anxiety, negative life events, emotion regulation, and coping. The findings indicated the presence of general risk factors (e.g., negative life events and poor coping) that increase the likelihood that adolescents will engage in any of a range of maladaptive behaviors. The probability of at-risk adolescents engaging in NSSI was increased by psychological states (i.e., rumination and poor self-esteem), whereas socio-demographic and personality traits were associated with firesetting. Implications for prevention and early intervention initiatives are discussed