Whole-brain mapping of afferents to the anterior cingulate cortex in adult mice.

The anterior cingulate cortex (ACC) is critical for pain perception, emotion and cognition. Previous studies showed that the ACC has a complex network architecture, which can receive some projection fibers from many brain regions, including the thalamus, the cerebral cortex and other brain regions. However, there was still a lack of whole-brain mapping of the ACC in adult mice. In the present study, we utilized a rabies virus-based retrograde trans-monosynaptic tracing system to map whole-brain afferents to the unilateral ACC in adult mice. We also combined with a new high-throughput, high-speed and high-resolution VISoR imaging technique to generate a three-dimensional whole-brain reconstruction. Our results showed that several principal groups of brain structures send direct monosynaptic inputs to the ACC, including the cerebral cortex, amygdala, striatum, the thalamus, and the brainstem. We also found that cortical neurons in the ACC mainly receive ipsilateral monosynaptic projections. Some cortical areas and forebrain regions also bilaterally projected to the ACC. These findings provide a complete analysis of the afferents to the ACC in adult mice, and whole-brain mapping of ACC afferents would provide important anatomic evidence for the study of pain, memory, and cognition.