Circuits Regulating Pleasure and Happiness in Schizophrenia: The Neurobiological Mechanism of Delusions

A recently developed model describes how evolutionary old neuronal systems allow freemoving animals, including humans, to escape from threats and discomfort and to acquire sufficient necessities to maintain life and to continue as a species. The amygdala has an essential role in regulating these fundamental reward-seeking and misery-fleeing behaviours. This is probably related to the ancient character of the corticoid and ganglionic parts of the amygdaloid complex. During evolution almost the entire ventral and lateral pallium (cortex) of the first vertebrates went up into the superficial and deep amygdalar nuclei, and their entire striatum and pallidum went up into the extended amygdala. An important role of the amygdala is selecting the sensory cues which are relevant for reward-seeking and misery-fleeing behaviour and should be paid attention to in order to increase the animal’s chances. This corresponds to attentive salience. Disturbances of this process in humans may lead to delusions. It has been suggested that in patients with schizophrenia this aberrant salience results from dopaminergic hyperactivity. The authors of this chapter believe that aberrant salience can result from dysfunctions everywhere within the chain: neocortex, corticoid amygdala, hippocampal complex, medial septum, medial habenula, midbrain nuclei and ventral tegmental area