SPLTRAK Abstract Submission
Two parallel pathways for olfactory processing in the mammalian brain
Honggoo Chae, Arkarup Banerjee, Dinu F. Albeanu
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, United States

Understanding the interplay between feedforward and feedback signals across interconnected brain areas is essential for unveiling the computations they perform. Across the brain, specialized long-range circuits support different streams of processing and broadcast multiple features of sensory stimuli and diverse substrates for planning and execution of motor actions. To date, the logic of information flow within the early mammalian olfactory system remains poorly understood. It is not known whether different projection neurons carry different signals to particular areas, and to what degree feedback from different target brain areas to the sensory periphery is specific to their input channels. Here we find that activity of the two classes of olfactory bulb outputs, the mitral and tufted cells (MCs and TCs) which innervate distinct sets of higher brain areas, including the piriform cortex (PC) versus the anterior olfactory nucleus (AON), is in turn regulated by differential feedback from these areas via multiphoton calcium imaging in awake head-fixed mice. Overall, feedback signals from PC and AON complemented each other in controlling the response amplitude, timing and pairwise correlation of odor representations at the level of mitral versus tufted ensembles, in a stimulus and cell specific manner. Furthermore, odor specific, robust sensory representations emerge already in the bulb outputs. TCs ensemble substantially outperformed MCs in decoding concentration invariant stimulus identity, while operating in largely a feedforward fashion. In contrast, the odor decoding performance of MCs was further drastically impaired by removal of PC feedback. These results identify two parallel feedforward-feedback loops in the early olfactory system, and indicate they have specialized roles in odor processing.