The Disordered Mind: What Unusual Brains Tell Us About Ourselves

by Eric R. Kandel

All of our positive emotions, our feelings of pleasure, can be traced to the neurotransmitter dopamine. Although our brain contains relatively few dopamine-producing neurons, they play an outsized role in the regulation of behavior, largely because of their intimate involvement with the production of pleasure. First discovered in the 1950s by the Swedish pharmacologist Arvid Carlsson, dopamine is released primarily by neurons in two regions of the brain: the ventral tegmental area and the substantia nigra (fig. 9.1). Neurons in the ventral tegmental region extend their axons to the hippocampus, which is involved in the memory of people, places, and things, and to the three most important brain structures for regulating emotion: the amygdala, which orchestrates emotion; the nucleus accumbens, a region of the striatum that mediates the impact of emotion; and the prefrontal cortex, which imposes will and control on the amygdala. This communications network, known as the mesolimbic pathway, is the major network in the brain’s reward system. It puts dopamine-producing neurons in a position to broadcast information widely, including to regions throughout the cerebral cortex.