centralcomplex

The central complex, sometimes referred to as the central complex neuropil, is a midline brain structure found in many arthropods, most notably insects. It comprises a set of interconnected substructures at the center of the brain, including the protocerebral bridge, fan-shaped body, ellipsoid body, and paired noduli. Together these regions form a compact network that integrates sensory information and coordinates motor output.

The central complex receives multimodal input from the optic neuropil, mushroom bodies, and other higher centers, and sends information to thoracic motor circuits via descending pathways through the lateral accessory lobes and related tracts. Its architecture features columnar neurons linking the protocerebral bridge, fan-shaped body, and ellipsoid body, along with ring neurons that channel information into the ellipsoid body. In many species, specific neuron types have been characterized as encoding heading directions or shaping motor commands.

Functions attributed to the central complex include navigation and spatial orientation, where it is thought to host a compass-like representation of heading and support path integration, enabling an animal to maintain orientation relative to landmarks and self-motion. It also participates in sensorimotor integration, decision making related to turning or proceeding, and the coordination of locomotion. In the fruit fly Drosophila melanogaster, genetic and imaging studies link CX activity to heading estimation and gaze stabilization, and perturbations through optogenetics can alter navigation behavior.

The central complex is a focal topic in insect neurobiology, with ongoing research aimed at mapping its microcircuits and their behavioral roles. Its study informs broader questions about how brains convert sensory inputs into action and maintain stable internal spatial representations across species.