Circuits that subserve similar functions are grouped in neural systems that serve broader behavioral purposes.
https://www.ncbi.nlm.nih.gov/books/NBK11061/
Canonical circuit for neocortex
Feedforward connectivity within the visual system
Feedback connectivity within the visual system
Sensory-motor coordination.
Inverse model, neural emulator.
Hummunculus
Sleep switch
REM sleep subcortical circuitry