akumbenskjernen

The nucleus accumbens (NAcc) is a brain structure located in the ventral striatum of the basal forebrain. In Danish and Norwegian usage it is referred to as akumbenskjernen. It consists of two main subregions, the core and the shell, which have distinct patterns of connectivity and function.

Anatomically, the nucleus accumbens receives dopaminergic input from the ventral tegmental area and glutamatergic input from the prefrontal cortex, amygdala, and hippocampus. It projects to the ventral pallidum and other basal ganglia structures, forming part of a loop that links motivation and action. The core and shell subregions differ in their connectivity and outputs, supporting somewhat different aspects of processing.

Functionally, the nucleus accumbens is central to reward processing, reinforcement learning, and goal-directed motivation. It helps encode reward prediction errors and mediates approach behavior in response to reward cues. The shell is more closely tied to the affective value of rewards, while the core supports cue-driven actions and motor responses.

Clinical relevance includes involvement in addiction and compulsive behaviors, as dopaminergic signaling in the NAcc contributes to drug-seeking and craving. Altered activity has been linked with anhedonia and certain mood disorders. Deep brain stimulation and pharmacological studies have explored NAcc modulation in treatment-resistant conditions.

In research, the nucleus accumbens is a focal point in studies of reward circuitry across species, with converging evidence from neuroimaging, electrophysiology, and lesion studies. It remains a key structure for understanding how motivation, reward, and decision making influence behavior.