Stimulation of the nucleus accumbens is primarily expected to alleviate which symptom of depression?

The nucleus accumbens is a critical structure in the brain's reward circuitry and is heavily involved in the processing of pleasure and reward. When stimulated, it is particularly effective in enhancing motivational and pleasurable responses, which are directly related to feelings of enjoyment and satisfaction.

Anhedonia, characterized by a reduced ability to experience pleasure, is a core symptom of depression. By stimulating the nucleus accumbens, the brain's reward pathways can be activated, contributing to the alleviation of anhedonia. This activation may help individuals regain interest in activities that were once enjoyable, thus addressing one of the hallmark symptoms of depression.

In contrast, while difficulty concentrating, fatigue, and insomnia can be associated with depression, they are not as directly linked to the dysfunction of reward pathways. Addressing those symptoms may require different therapeutic approaches, focusing on cognitive processes, energy levels, or sleep regulation, rather than the direct modulation of the brain's reward system that stimulation of the nucleus accumbens provides.