Two core motivational systems have been conceptualized as underlying emotion and behavior. The approach system drives the organism toward stimuli or events in the environment, and the avoidance system instead deters the organism away from these stimuli or events. This approach—avoidance dichotomy has been central to theories of emotion. Advances in neuroscience complementing well-designed behavioral experiments have begun to elucidate the neural mechanisms underlying approach—avoidance motivation, suggesting that these two systems exist in parallel and are lateralized in the brain. This (...) review explores the notion of approach—avoidance and the cerebral lateralization of these motivational tendencies. (shrink)

Evaluative processes have their roots in early evolutionary history, as survival is dependent on an organism’s ability to identify and respond appropriately to positive, rewarding or otherwise salubrious stimuli as well as to negative, noxious, or injurious stimuli. Consequently, evaluative processes are ubiquitous in the animal kingdom and are represented at multiple levels of the nervous system, including the lowest levels of the neuraxis. While evolution has sculpted higher level evaluative systems into complex and sophisticated information-processing networks, they do not (...) come to replace, but rather to interact with more primitive lower level representations. Indeed, there are basic features of the underlying neuroarchitectural plan for evaluative processes that are common across levels of organization—including that of evaluative bivalence. (shrink)