Research Highlight: Persistent Structural Plasticity Optimizes Sensory Information Processing in the Olfactory Bulb

The olfactory bulb (OB) has highly dynamic structural plasticity in adult-born synapses, yet the OB network supports stable perceptual function. To resolve this apparent paradox, ENP group leader Pierre-Marie Lledo and colleagues, using in vivo 2-photon imaging to track individual adult-born neurons in the OB, show that the highly dynamic nature of granule GABAergic interneuron (GC) spines mirrors structural reorganization of the reciprocal dendro-dendritic synapses that GCs make with excitatory mitral cell neurons (MC). Furthermore, the authors used computational modeling and showed that GCs are able to efficiently remap their connectivity with MCs when presented with a new odor environment. This suggests that although OB spines are highly dynamic, the massive remapping of the network of GC/MC synapses can maintain stable odor representations, yet be qualified to adapt.

Check out the article:

Persistent Structural Plasticity Optimizes Sensory  Information Processing in the Olfactory Bulb. Kurt A. Sailor,Matthew T. Valley, Martin T. Wiechert, Hermann Riecke, Gerald J. Sun, Wayne Adams, James C. Dennis,  Shirin Sharafi, Guo-li Ming, Hongjun Song, and Pierre-Marie Lledo.  Neuron 91, 384–396, 2016

Figure legend:

A) Images of the same adult-born granule cell dendritic segment (green fluorescent protein) imaged at a 2-day interval over a week showing appearance, stability and loss of spines. 

B) Dendritic segment of a mitral cell neuron with GABAergic post-synaptic sites labeled with a fluorescent protein fused to gephyrin showing synaptic structural changes at a 2-day.

C) Quantification of granule cell (GC) spine dynamics and that of tufted and mitral cell (TC, MC) gephyrin puncta dynamics showing matching turnover of synapses.

D) Schematic cartoon of computation model with input pattern of odor-evoked activity being relayed to mitral cells (MCs) and granule cell (GCs) spine turnover modifying the output pattern.

E) Plot of pattern stability in the computational model over the span of days showing that with structural plasticity, despite the granule cell (GC) low pattern stability (high dynamics), their re-arrangement in synapses is still able to maintain stable sensory representations with high pattern stability in mitral cells (MCs)