The central nucleus of the amygdala projection to dopamine subpopulations in primates

The dopamine system plays a major role in responses to potentially rewarding stimuli. An important input to the dopamine neurons is derived from the central nucleus of the amygdala. The central nucleus is a complex structure consisting of several subdivisions with distinct histochemical, morphologic, and connectional features. The central nucleus subdivisions are therefore likely to have specific inputs to the dopamine neurons. The midbrain dopamine cells are divided into dorsal and ventral subpopulations. We determined the organization of inputs from the central nucleus subdivisions to the dopamine subpopulations in monkeys. The dorsal tier neurons receive relatively greater central nucleus input compared to the ventral tier. Within the ventral tier, the central nucleus projects to the densocellular region, but not the cell columns. Furthermore, the midbrain subpopulations receive a differential projection from specific central nucleus subterritories. The medial subdivision of the central nucleus has the greatest input to the dopamine system, and projects throughout the dorsal tier and densocellular regions. This indicates that the medial subdivision influences not only the ventral striatum but also more dorsal striatal areas, through its inputs to these dopamine subpopulations. In contrast, the capsular subdivision of the lateral central nucleus and the amygdalostriatal area project preferentially to the dorsal tier, which selectively modulates the ventral striatum and cortex. The central core of the lateral central nucleus is unique in its restricted projection to the lateral substantia nigra in the region of the nigrotectal pathway. Taken as a whole, the central nucleus-nigral pathway provides a route for affectively significant stimuli to modulate the DA system, influencing the initiation of behavioral responses.