Olfaction in insects

Abstract

Odorants provide insects with crucial information about their environment and trigger various insect behaviors. A remarkably sensitive and selective sense of smell allows the animals to detect extremely low amounts of relevant odorants and thereby recognize, e.g., food, conspecifics, and predators. In recent years, significant progress has been made to­wards understanding the molecular elements and cellular mechanisms of odorant detection in the antenna and the principles under­lying the primary processing of olfactory signals in the brain. These findings show that olfactory hairs on the antenna are specifically equipped with chemosensory detector units. They contain several binding proteins, which transfer odorants to specific receptors resid­ing in the dendritic membrane of olfacto­ry sensory neurons (OSN). Binding of odor­ant to the receptor initiates ionotropic and/or metabotropic mechanisms, translating the chemical signal into potential changes, which alter the spontaneous action potential frequency in the axon of the sensory neurons. The odor-dependent action potentials propagate from the antennae along the axon to the brain leading to an input signal with­in the antennal lobe. In the antennal lobe, the first relay station for olfactory information, the input signals are extensively processed by a complex network of local interneurons be­fore being relayed by projection neurons to higher brain centers, where olfactory perception takes place.