Functional-anatomical implications of the nucleus accumbens core and shell subterritories.

The nucleus accumbens, a major part of the ventral striatum, comprises numerous subterritories and compartments, of which the core and shell appear to be dominant. Shell exhibits greater chemical neuroanatomical diversity than core and is rather directly connected to it by a robust, feed-forward, striatopallido-thalamocortico-striatal pathway. Shell and extended amygdala share afferents, but the two are distinguished by their outputs, strongly toward cortex for shell and descendent toward brain stem effector sites for extended amygdala. Shell responds independently to stimulation by excitatory amino acids and dopamine, which are more mutually permissive in the core. Accordingly, the shell responds to a broad variety of physiological and pharmacological stimuli, including psychomotor and opioid drugs. Whereas locomotion and oro-facial movements are elicitable from the shell, lesions and blockade of EAA transmission in the core reduce locomotion. It is hypothesized that core-shell has a feed-forward functional organization.