Lateral olfactory processing

A recent publication reports a series of findings demonstrating a network of inhibitory connections between antennal lobe glomeruli in the Drosophila olfactory system. These connections include a GABA-mediated presynaptic inhibition that suppresses transmitter release from olfactory receptor neuron terminals. This presynaptic inhibition is organized on an interglomerular basis, such that the inhibition scales with the global sensory input the antennal lobe, rather than with local inputs to specific glomeruli. This functional organization suggests that the inhibition may serve as a general gain control for olfactory input. These inhibitory connections were also shown to narrow the range of odorants to which the corresponding principal neurons respond, thus improving the efficiency of the neural code for odors. The Drosophila antennal lobe thus shares important organizational features with the mammalian olfactory bulb.