Abstract
Brain function is not simply the sum of individual neuronal activities, but rather emerges from functional neural circuits comprising thousands to millions of neurons with specific topological structures and dynamic properties. Investigating the functions and information-processing architectures of these neural circuits is essential for understanding how the brain performs "computation" and "operation." Biological neural regulatory networks are captivating due to their extensive utilization of diverse signaling molecules for interneuronal communication. Neurotransmitters, receptors, and neurons together compose neuroregulatory circuits, which act as fundamental functional units in the network for generating behavioral instructions. However, the discovery and decipherment of neural circuits remain challenging, due to the necessity of comprehending the functions of signaling molecules and neuronal cells, as well as their regulatory mechanisms. In this review, we focus on four biogenic amines signals, including dopamine, serotonin, octopamine and tyramine, and discuss their regulatory roles with their receptors in Caenorhabditis elegans neural circuits. In particular, we summarize the functional roles of the biogenic amine neurons and their complex interaction mechanisms in neural circuits. We also provide perspectives on the fine-scale neural connectivity, which will bridge microscopic neuronal activity with macroscopic cognitive behaviors, offering a theoretical framework for further elucidating the neural mechanisms underlying brain adaptation, learning, and memory.