Tools for Neural Circuit Tracing Based on Neurotropic Viruses

The brain is probably the most complex system. Neurocircuits, formed by various types of neurons through synaptic connections, are the basis of brain functions, from the basic homeostasis, senses and perception, for learning, memory, decision-making, and consciousness. Therefore, it is of great significance to understand the component and working principle of neurocircuits, so as to recognize, utilize and protect the brain. Techniques for exploring the structure and function of neurocircuits include circuit-tracing, manipulating, imaging and data-analyzing. In this paper, we focus on the neurocircuit tracers based on neurotropic viruses and its application technology. The categories and characteristics, genetic modification, selection principles and application limitations of commonly used neurotropic viral tools will be discussed. The non-transsynaptic tracer system, the trans-monosynaptic tracer system and the trans. multisynaptic tracer system are also introduced to help readers understand the commonly used circuit tracing methods and research progress.