Making Waves: Initiation and Propagation of Corticothalamic Ca2+ Waves In Vivo

Neuron, 2013, http://dx.doi.org/10.1016/j.neuron.2013.01.031, Volume 77, Issue 6, 1136-1150 published on 20.03.2013
Neuron, online article
Corticothalamic slow oscillations of neuronal activity determine internal brain states. At least in the cortex, the electrical activity is associated with large neuronal Ca2+ transients. Here we implemented an optogenetic approach to explore causal features of the generation of slow oscillation-associated Ca2+ waves in the in vivo mouse brain. We demonstrate that brief optogenetic stimulation (3–20 ms) of a local group of layer 5 cortical neurons is sufficient for the induction of global brain Ca2+ waves. These Ca2+ waves are evoked in an all-or-none manner, exhibit refractoriness during repetitive stimulation, and propagate over long distances. By local optogenetic stimulation, we demonstrate that evoked Ca2+ waves initially invade the cortex, followed by a secondary recruitment of the thalamus. Together, our results establish that synchronous activity in a small cluster of layer 5 cortical neurons can initiate a global neuronal wave of activity suited for long-range corticothalamic integration.  

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