Anesthesia and the Merry-go-round of Information in the Brain

It is widely believed that anesthesia is a syndrome caused by drug-induced disruption of coordination within and between neuronal networks. The underlying teleological assumption is that normal function of the central nervous system requires precise electrical and chemical communication between neurons, and communication implies flow of “information.” In this issue of Anesthesiology is an article by Chang et al.¹  in which isoflurane was given to a nematode (Caenorhabditis elegans), and the resultant real-time changes in activity of about half of its 302 neurons were visualized using high-resolution calcium fluorescence imaging. In this study, the authors focused on how anesthesia alters interneuronal coupling by measuring the entropy of the calcium transients in the imaged neurons. The meaning of the word “entropy” is intuitively difficult. It is often used as a synonym for disorder, uncertainty, or unpredictability. To take the extreme examples: if a neuron has no activity (a...