When odors enter the nose, the airborne chemicals bind with receptors on olfactory sensory neurons. This information is relayed to the olfactory bulb, the first processing station in olfaction. Neurons of the olfactory bulb project directly to the piriform cortex resulting in a two or at most, three, synapse path between the peripheral sensor and the cortex. Interestingly, in the olfactory bulb there is a clear spatial representation of odor component identity. However, just one synapse away in the piriform cortex, there is complete transformation to odor representations that lack spatial structure. We want to understand the circuit mechanisms that underlie this transformation.
Our hope is that this enticingly simple pathway will provide insight into how sensory information is represented in neural activity and transferred between brain areas to inform our perception of the world around us.
Why olfactory cortex?
It is intriguing to study a structure that is at the interface of early sensory processing and higher-level processes that underlie perception.
One of the most interesting features of the piriform cortex is that odors are represented in the activity of ensembles of neurons that are uniformly distributed over the length of the structure. Thus, unlike the olfactory bulb or other primary sensory cortices, the piriform cortex does not appear to use spatial location to represent stimulus identity. Rather, such distributed assembly activity is more common in areas responsible for higher-order Gestalt representations. This suggests that the piriform cortex not only relays sensory information, but plays an important early role in the long-term representation of odor information. We are investigating in the synaptic, cellular and circuit mechanisms that underlie assembly formation and odor coding by the piriform cortex.