Olfactory-induced behaviors such as homing, food or mate searching are crucial for the survival and reproduction of most animals. A neural basis for such behaviors in vertebrates was recently uncovered using a basal vertebrate model, the lamprey, and consists of a neural pathway extending from the medial olfactory bulb, a first-order relay of olfactory information in the brain, to locomotor regions. The new study by Daghfous et al. investigated modulatory mechanisms acting on this neural pathway, discovering a novel pathway linking olfactory and motor centers in the brain, indicating that olfactory inputs can activate locomotor centers via two distinct pathways. Both pathways are strongly modulated by the neurotransmitter GABA in the olfactory bulb. The existence of segregated olfactory subsystems in lampreys sheds light on the evolution of olfactory systems in vertebrates. The image shows how the organization of the lamprey olfactory bulb resembles that of mammals; axons of olfactory sensory neurons (green) enter the olfactory bulb and form glomeruli where they synapse with dendrites of projection neurons (blue). Daghfous et al.

Image Credit: Daghfous et al.