Plasticity of Synaptic Microcircuits in the Mushroom-Body Calyx of the Honey Bee

Abstract

Mushroom bodies (MBs) are prominent neuropils in the insect brain that have been implicated in higher order processing such as sensory integration, learning and memory, and spatial orientation. Hymenoptera, like the honey bee, possess particularly large MBs with doubled MB calyces (major sensory input structures of the MBs) that are divided into compartments. In this review we focus on characteristic modular synaptic complexes (microglomeruli, MG) in the honey bee MB calyx (CA). The main components of MG comprise a presynaptic bouton from projection neurons (PNs) (e.g. olfactory, visual), numerous dendritic spines from MB intrinsic neurons (Kenyon cells, KC), and processes from recurrent GABAergic neurons. Recent work has demonstrated a remarkable structural plasticity of MG associated with postembryonic brood care, age, sensory experience, and stable long-term memory. The mechanisms and functional significance of this neuronal plasticity are discussed and related to behavioral plasticity and social organization.