Anesthesia differentially modulates spontaneous network dynamics by cortical area and layer

Sellers KK, Bennett DV, Hutt A, Fröhlich F. J Neurophysiol. 2013 Dec;110(12):2739-51 PMID: 24047911 Anesthetics are generally thought to depress neuronal activity, but that's not always the case. Current thinking seems to be that they work by modulating network communication, even though that may mean increasing activity in some cases. In this paper, they looked at how 0.5, 0.75, and 1.0% isofluorane modulates activity in the visual cortex and the association cortex at the field and multiunit levels in ferrets. What they found was that the different regions responded differently to anesthesia, and even different cortical layers within the same area responded differently. For instance, the overall activity of the visual cortex did not change, there was an increase in layer IV neuron activity and a decrease in other layers. So while they were able to see the slow oscillations that have previously been seen in anesthesia, they were able to measure differences between areas and layers. I wanted to read this paper because we are starting to examine neuronal activity, and we've had questions of what sedation can do to our animals. I didn't really get any answers to my questions, but I have more questions now and I realize that things could get a lot more complicated. I guess we should be careful about how we do our upcoming MeMRI studies. I guess this also makes me question some of the early studies showing greater Mn uptake as sedation wore off, but that's a whole different issue right there. -DH