Positive feelings like pleasure, or hedonic liking, are e.g. linked to food and procreation and as such crucial for survival of the individual and the species. Romantic love, maternal love and other social pleasures belong also to this basic set. And than there are higher order pleasures including artistic, musical, altruistic, monetary and transcendent pleasures. A pathological loss or absence of such positive feelings, anhedonia, is present in affective disorders, such as depression, schizophrenia, autism and addiction.
Reward is the active process of the brain that reacts to a pleasant stimulus. Liking, wanting and learning of reward are represented in different brain areas. The occurrence of pleasure is coded by neural activity in many brain sites, including the prefrontal cortex, amygdale, thalamus, nucleus caudatus, nucleus accumbens and the ventral pallidum. The brain regions involved differ partly between the sexes, and sex hormones are involved in this process.
The prefrontal cortex (PFC) is the apex of pleasure representation, and from the coding of the reward in this brain area it can be used to influence subsequent decisions and behaviors. But the PFC is not a pleasure generating center. Lobectomy patients can still feel pleasure of food, sex and other rewards. As appears from lesions and stimulation by deep brain electrodes (DBE), pleasure can be generated by a smaller subset of hedonic hotspots, such as the septum and nucleus accumbens. Neurotransmitters of different chemical nature are involved in pleasure and reward.
The dopaminergic system of the ventral tegmentum with terminals in the nucleus accumbens is involved in predictive, motivational or attentional properties. Electrodes in the septum/accumbens may produce feelings of sexual arousal and may enhance motivation, while never producing orgasm. In addition, endogenous opioids are involved. Falling in love is accompanied by an activation of the stress-axis. For romantic love, orgasm, pair bonding and maternal love the central vasopressin and oxytocin projections are crucial. Deficiencies in these neuropeptide systems have been found in autism.