What is the role of traveling waves in circuit formation during cortical development?

Question

Propagating waves of activity have been characterized in various regions of the brain such as the visual cortex (Nauhaus et al., 2012). Recently they have been reported for the first time to occur transiently during the developing cerebellum (Watt et al., 2009).

I'm curious as to how they would be important during early development and why they are transient which I'm sure the authors have moved on to try and answer as well.

I've heard before about neuronal activity being important for pruning and forming correct connectivity within a network. For example waves of activity has been shown to be required for the development of precise retinotopic maps (Chang et al., 2005).

I'm not an expert and not familiar with the history or literature of neurodevelopment, so would like to ask if someone who may be more knowledgeable to describe what's known about wave activity during early brain development in other brain areas. How do waves help with proper circuit formation in these other regions? I am hoping this might provide insight to its role in the cerebellum.

_{Nauhaus, I., Busse, L., Ringach, D. L., and Carandini, M. (2012). Robustness of traveling waves in ongoing activity of visual cortex. The Journal of Neuroscience, 32(9):3088–3094. doi:10.1523/JNEUROSCI.5827-11.2012
Watt, A. J., Cuntz, H., Mori, M., Nusser, Z., Sjöström, P. J., and Häusser, M. (2009). Traveling waves in developing cerebellar cortex mediated by asymmetrical purkinje cell connectivity. Nature neuroscience, 12(4):463–473. doi:10.1038/nn.2285
Cang, J., Renterı́a, R. C., Kaneko, M., Liu, X., Copenhagen, D. R., and Stryker, M. P. (2005). Development of precise maps in visual cortex requires patterned spontaneous activity in the retina. Neuron, 48(5):797–809. doi:10.1016/j.neuron.2005.09.015}

Answer 1

Traveling waves are a developmental mechanism to "prime" neural circuits. In a mature adult, certain mechanisms allow the strengthening and weakening of synapses (LTP/LTP, dendritic spine growth, etc...). These same mechanisms are used during development to achieve initial connectivity. For these to work however, spiking activity must be present. Experience will later produce complex and meaningful patterns of activity between structures, that will in turn produce complex and meaningful patterns of connectivity. Until that point, the neural structures must be synaptically linked so that learning can begin after birth.

Certain cellular mechanisms guide axon growth, and this transient bursting activity "captures" the specificity of these growths as synapses. When this bursting activity is disrupted, the precise topographical connections are lost.

References

http://www.sciencedirect.com/science/article/pii/0896627393901228 http://www.annualreviews.org/doi/abs/10.1146/annurev.neuro.28.061604.135714?journalCode=neuro