Cortical Feedback Control of Olfactory Bulb Circuits

Neuron. 2012 Dec 20;76(6):1161-74. doi: 10.1016/j.neuron.2012.10.020.

Abstract

Olfactory cortex pyramidal cells integrate sensory input from olfactory bulb mitral and tufted (M/T) cells and project axons back to the bulb. However, the impact of cortical feedback projections on olfactory bulb circuits is unclear. Here, we selectively express channelrhodopsin-2 in olfactory cortex pyramidal cells and show that cortical feedback projections excite diverse populations of bulb interneurons. Activation of cortical fibers directly excites GABAergic granule cells, which in turn inhibit M/T cells. However, we show that cortical inputs preferentially target short axon cells that drive feedforward inhibition of granule cells. In vivo, activation of olfactory cortex that only weakly affects spontaneous M/T cell firing strongly gates odor-evoked M/T cell responses: cortical activity suppresses odor-evoked excitation and enhances odor-evoked inhibition. Together, these results indicate that although cortical projections have diverse actions on olfactory bulb microcircuits, the net effect of cortical feedback on M/T cells is an amplification of odor-evoked inhibition.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cerebral Cortex / cytology
  • Cerebral Cortex / physiology
  • Feedback, Physiological / physiology*
  • In Vitro Techniques
  • Interneurons / cytology
  • Interneurons / physiology
  • Mice
  • Mice, Transgenic
  • Olfactory Bulb / cytology*
  • Olfactory Bulb / physiology
  • Olfactory Pathways / cytology
  • Olfactory Pathways / physiology*
  • Olfactory Perception / physiology*
  • Pyramidal Cells / cytology
  • Pyramidal Cells / physiology*