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Published on: March 21, 2012
Lateral dendritic shunt inhibition can regularize mitral cell spike patterning
François David1, Christiane Linster, Thomas A Cleland
1Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA. fdavid@olfac.univ-lyon1.fr
Abstract:
Mitral cells, the principal output neurons of the olfactory bulb, receive direct synaptic activation from primary sensory neurons. Shunting inhibitory inputs delivered by granule cell interneurons onto mitral cell lateral dendrites, while poorly positioned to prevent spike initiation, are believed to influence spike timing and underlie coordinated field potential oscillations. We investigated this phenomenon in a reduced compartmental mitral cell model suitable for incorporation into network simulations. Lateral dendritic shunt conductances delayed spiking to a degree dependent on both their electrotonic distance and phase of onset. Moreover, when the afferent activation of mitral cells was loosely coordinated in time, recurrent inhibition significantly narrowed the distribution of mitral cell spike times, illustrating a tendency towards coordinated synchronous activity. However, if mitral cell activity was initially disorganized, recurrent inhibition actually increased the variance in spike timing. This result suggests an essential role for early mechanisms of temporal coordination in olfaction, such as sniffing and the initial synchronization of mitral cell intrinsic oscillations by periglomerular cell-mediated inhibition.
Insights
Shunting inhibition in mitral cells influences spike timing. Coordinated inputs promote synchronous activity, while disorganized inputs increase timing variability, highlighting the importance of early temporal coordination in olfaction.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Olfactory System Research
Background:
- Mitral cells are key output neurons in the olfactory bulb.
- Granule cell interneurons provide shunting inhibition to mitral cell dendrites.
- This inhibition is thought to affect spike timing and field potential oscillations.
Purpose of the Study:
- To investigate the impact of shunting inhibition on mitral cell spike timing.
- To model the role of recurrent inhibition in neural network simulations.
- To understand the conditions under which inhibition promotes or disrupts temporal coordination.
Main Methods:
- Developed a reduced compartmental mitral cell model.
- Simulated shunting inhibitory inputs at varying electrotonic distances and onset phases.
- Analyzed the effect of inhibition on spike timing under different afferent activation patterns.
Main Results:
- Lateral dendritic shunting conductances delayed spiking, with effects dependent on distance and phase.
- Recurrent inhibition narrowed spike time distributions when afferent activation was loosely coordinated.
- Conversely, recurrent inhibition increased spike timing variance for initially disorganized mitral cell activity.
Conclusions:
- Shunting inhibition plays a crucial role in modulating mitral cell spike timing.
- Temporal coordination of inputs is essential for recurrent inhibition to promote synchronous activity.
- Early sensory processing mechanisms, like sniffing, are vital for establishing temporal order in olfaction.
