We thank Dr. Mashour for his interest in our article.1It is hard to avoid getting entangled in semantic issues in this type of research. As Dr. Mashour has indicated, the problem with traditional heuristic definitions of sleep stage is that they are arbitrarily defined and lack a proper causal linkage with sleep functions. Thus, we are in favor of Dr. Mashour's term “protoconsciousness” to describe states of mentation associated with activation (depolarization) of the cerebral cortex, but which fall short of wakeful responsiveness to the external world. These states are usually indicated by the increased electroencephalographic and bispectral index values and are common during general anesthesia.

*Royal Melbourne Hospital, Parkville, Victoria, Australia. kate.leslie@mh.org.au

Leslie K, Sleigh J, Paech MJ, Voss L, Lim CW, Sleigh C: Dreaming and electroencephalographic changes during anesthesia maintained with propofol or desflurane. Anesthesiology 2009; 111:547–55