Neuron
Volume 86, Issue 6, 17 June 2015, Pages 1461-1477
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Article
Cortical Feedback Decorrelates Olfactory Bulb Output in Awake Mice

https://doi.org/10.1016/j.neuron.2015.05.023Get rights and content
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Highlights

  • Piriform feedback to olfactory bulb is sparse, odor specific, and locally diverse

  • Distinct feedback axon types enhance or suppress their baseline activity to odors

  • Feedback responses are layer selective and can outlast odor stimulation by seconds

  • Piriform cortex decorrelates mitral but not tufted cells’ odor responses

Summary

The olfactory bulb receives rich glutamatergic projections from the piriform cortex. However, the dynamics and importance of these feedback signals remain unknown. Here, we use multiphoton calcium imaging to monitor cortical feedback in the olfactory bulb of awake mice and further probe its impact on the bulb output. Responses of feedback boutons were sparse, odor specific, and often outlasted stimuli by several seconds. Odor presentation either enhanced or suppressed the activity of boutons. However, any given bouton responded with stereotypic polarity across multiple odors, preferring either enhancement or suppression. Feedback representations were locally diverse and differed in dynamics across bulb layers. Inactivation of piriform cortex increased odor responsiveness and pairwise similarity of mitral cells but had little impact on tufted cells. We propose that cortical feedback differentially impacts these two output channels of the bulb by specifically decorrelating mitral cell responses to enable odor separation.

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