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Cortical feedback control of olfactory bulb circuits.
Alison M Boyd1, James F Sturgill, Cindy Poo
1Center for Neural Circuits and Behavior, Department of Neuroscience, University of California, San Diego, School of Medicine, La Jolla, CA 92093, USA.
Neuron
|December 25, 2012
Summary
Olfactory cortex feedback excites diverse bulb interneurons, influencing mitral and tufted (M/T) cell responses. Cortical activity amplifies odor-evoked inhibition in M/T cells, refining olfactory processing.
Area of Science:
- Neuroscience
- Olfactory System Research
- Sensory Processing
Background:
- Olfactory cortex pyramidal cells receive input from olfactory bulb mitral and tufted (M/T) cells.
- Cortical feedback projections to the olfactory bulb are known but their circuit-level impact remains unclear.
Purpose of the Study:
- To investigate the functional impact of olfactory cortex pyramidal cell feedback projections on olfactory bulb circuits.
- To elucidate how cortical feedback modulates olfactory bulb mitral and tufted (M/T) cell activity during odor perception.
Main Methods:
- Selective expression of channelrhodopsin-2 in olfactory cortex pyramidal cells.
- Electrophysiological recordings in vivo to assess M/T cell responses.
- Optogenetic activation of cortical feedback projections.
Main Results:
- Cortical feedback projections excite various olfactory bulb interneurons, including GABAergic granule cells.
- Cortical inputs preferentially target short axon cells, enhancing feedforward inhibition of granule cells.
- In vivo, cortical activation suppresses odor-evoked excitation and enhances odor-evoked inhibition in M/T cells.
Conclusions:
- Olfactory cortex feedback has diverse effects on olfactory bulb microcircuits.
- The net effect of cortical feedback is an amplification of odor-evoked inhibition in M/T cells.
- This feedback mechanism plays a crucial role in gating and refining olfactory sensory information processing.
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