protocerebrum

The protocerebrum is the anterior portion of the arthropod brain, forming the primary division of the supraesophageal ganglion in many groups, including insects. It functions as a major processing and integration center, especially for visual information and higher-order neural processing.

In insects, the optic lobes—comprising the lamina, medulla, and lobula—are embedded within the protocerebrum and receive direct input from the compound eyes. The protocerebrum also contains several higher-order centers, most notably the mushroom bodies (including their calyces and peduncles) and the central complex (which includes the protocerebral bridge, fan-shaped body, and ellipsoid body). These structures are associated with learning and memory, olfactory and multisensory integration, spatial orientation, and the coordination of movement.

Anatomical boundaries between the protocerebrum and adjacent regions such as the deutocerebrum and tritocerebrum can vary among taxa, and precise delineations are often defined by nerve tracts and organizational schemes rather than universal borders. While the specific arrangement of its neuropils differs across arthropods, the protocerebrum commonly includes the primary visual processing centers and key centers for higher cognitive functions.

Etymology and terminology: "protocerebrum" derives from Greek roots meaning "first brain," reflecting its position as the anterior, or primary, brain region in many arthropods.