Firing and wiring: Hebbian axonal remodelling in Xenopus

Editor's summary:

Correlated neuronal activity is generally thought to drive circuit remodeling in the central nervous system. This model, first proposed by Hebb, is strongly supported by several lines of evidence, though it has been difficult to directly observe such changes in real time. Munz et al. developed an experimental approach to watch structural remodeling of neuronal axons in vivo at high temporal resolution. They measured changes in synaptic efficacy while presenting specific patterned stimuli to test the Hebb model. Although the key predictions of Hebbian developmental plasticity were upheld, the mechanistic details of how this occurred were unexpected.

Article abstract by Munz et al.:

We examined how correlated firing controls axon remodeling, using in vivo time-lapse imaging and electrophysiological analysis of individual retinal ganglion cell (RGC) axons that were visually stimulated either synchronously or asynchronously relative to neighboring inputs in the Xenopus laevis optic tectum. RGCs stimulated out of synchrony rapidly lost the ability to drive tectal postsynaptic partners while their axons grew and added many new branches. In contrast, synchronously activated RGCs produced fewer new branches, but these were more stable. The effects of synchronous activation were prevented by the inhibition of neurotransmitter release and N-methyl-D-aspartate receptor (NMDAR) blockade, which is consistent with a role for synaptic NMDAR activation in the stabilization of axonal branches and suppression of further exploratory branch addition.

Funding from the Canadian Institutes of Health Research

From Martin Munz et al., SCIENCE 344:904 (2014). (http://www.sciencemag.org/content/344/6186/904)

Reprinted with permission from AAAS.

Link to abstract on Xenbase:

http://www.xenbase.org/literature/article.do?method=display&articleId=49053