Behavioral, neural and neurochemical basis of effort-related decision making

Effort-based decision-making refers to the process by which humans and animals choose between competing courses of action by weighing expected costs, in terms of effort, against anticipated benefits such as food reward. Although this topic has been the focus of extensive research, the behavioral, neural, and neurochemical mechanisms underlying effort-based decision-making are incompletely understood. In this review, I address these issues by focusing primarily on neurobiological studies in rodents. Using a broad range of behavioral tasks, the studies reviewed here point to a complex neural circuit underlying effort-based decision making. Key components of this circuit include the anterior cingulate cortex, the orbitofrontal cortex, the basolateral amygdala, the nucleus accumbens core and the ventral pallidum. Many of these studies do not allow for a clear dissociation of specialized roles for these regions, e.g., whether they encode effort, reward, or both. Instead, recent evidence suggests that effort-based decision making may depend on the coordinated activity across components of this neural circuit through which information from diverse neural sources is integrated in parallel. Multiple neurotransmitters and neuromodulators, as for instance, dopamine, noradrenaline, adenosine and ghrelin modulate the activity of this neural network. They likely act in concert to adapt the willingness to expend effort according to the organism's actual physiological state, the presence of environmental stimuli and the nature of available rewards, thereby supporting adaptive effort-related decision making. Implications of these findings are discussed with respect to the neural and neurochemical bases of motivational dysfunctions observed in disorders such as depression and apathy.