Brain mechanisms of emotion and decision-making

Emotions can be defined as states elicited by rewarding and punishing stimuli. The thesis is being developed that brains are designed around reward and punishment evaluation systems, because this is the way that genes can build a complex system that will produce appropriate but flexible decisions to increase their fitness.Direct neurophysiological and neuroimaging evidence is being obtained that primary (unlearned and gene-specified) reinforcers such as taste, pleasant touch, pain, oral texture including viscosity and fat texture, and oral temperature are decoded and represented in the orbitofrontal cortex of primates including humans. Similarly, previously neutral stimuli such as the sight of an object become associated with primary reinforcers by rapid and reversible stimulus–reinforcement learning implemented in the orbitofrontal cortex. Neuroimaging studies in humans show that reinforcers produced by taste, smell, touch, abstract monetary reward and social reinforcers are represented in the orbitofrontal cortex, and that the orbitofrontal cortex is also activated when an expected reward is not obtained. Neuroimaging studies are also showing strong effects of cognitive inputs on representations of rewards and punishers in the orbitofrontal cortex. The human orbitofrontal cortex is further implicated in decision-making by findings that visual discrimination reversal learning, and emotional behaviour and subjective emotional experience, are impaired in humans with discrete lesions of the orbitofrontal cortex, who may also be impulsive in their decision-making.