Final answer:
The ventral tegmental area (VTA) and the nucleus accumbens connect as part of the reward circuit in the brain, with dopaminergic neurons playing a key role in reward processing, motivation, and reinforcement learning. The complex reward circuit also includes interactions with the amygdala and hippocampus, important for emotional and memory processes.
Step-by-step explanation:
In regard to the reward circuit in the brain, two crucial structures connect as part of this system: the ventral tegmental area (VTA) and the nucleus accumbens. Dopaminergic neurons found in the VTA send projections to the nucleus accumbens, among other areas, forming part of the mesolimbic pathway which is essential for reward processing, motivation and reinforcement learning. This dopaminergic pathway is involved in the pleasurable sensation and the reinforcement that encourages us to repeat behaviors. The VTA also communicates with the amygdala and the hippocampus, crucial for memory and emotional processing, indicating the reward circuit's broader impact on learning and behavior.
The nucleus accumbens further plays a significant role in limbic-motor integration, facilitating behaviors associated with reward such as stimulus conditioned responsiveness and locomotor activity. Inputs to the basal nuclei, like the striatum, also impact the reward circuit through glutamatergic inputs from the cortex which can control dopaminergic neurons in the SN-VTA through striatal feedback projections. It is the intricate connections between these structures, all coupled with the effects of dopamine, that constitute the complex workings of the reward circuit within the human brain.