Anesthesia, Consciousness, and Language

I was fascinated to read the recent paper and editorial concerning anesthesia and consciousness, and I wondered whether we might learn more about the effects of anesthesia if we consider one of the brain’s most impressive faculties—that of human language.^1,2  There have been a number of reports of patients fixating on a second language while under the effects of anesthesia, either during sedation or sometimes for hours postoperatively.^3–8  In all cases, the switching of the production of speech to exclusively the patient’s second language appears to be a direct and involuntary effect of anesthesia, one that spontaneously resolves without sequelae once recovery is complete. Patients often report not being able to remember speaking in their second language after the fixation event, and more intriguingly, even deny an ability to speak their second language at all (when not having spoken it voluntarily for many years).

It is well known that the production of a first language is associated with Broca’s area, while production of a second language that is acquired after approximately the age of seven can involve a number of cortical areas in both hemispheres.⁹  I previously have hypothesized that this fact might explain why it is that language switching under the effects of anesthesia appears to occur in only one direction, that is, from first to second language.⁹  The idea being that if there are a number of scattered brain areas associated with a second language, but only one area for a first language, there may be a greater chance that an anesthetic agent that differentially affects brain structures could impair the first language while functionally sparing some of the more numerous areas associated with the second language.

Hashmi et al. provide quantitative evidence suggesting that something like this may, in fact, be occurring.²  If loss of consciousness is due to the blocking of certain information “hubs” in the brain, reducing the efficiency of global information transfer, even in the face of remaining local brain activity, then Broca’s area is likely to be such a hub for the production of the patient’s first language. With a blocked first-language hub, local networks that remain active may contain some of the more numerous areas capable of producing the patient’s second language. This also could explain why patients often do not remember speaking in their second language, given the impairment of global information networks and conscious awareness. This language switching phenomena may be underreported. If the patient’s second language is not recognized by those attending the patient at the time, it is likely that the fixation event would simply be put down to postoperative confusion (in three of the known cases only a single staff member spoke the patient’s second language). If a way could be devised to study this rare phenomenon more systematically, the large number of anesthetic procedures conducted throughout the world every day would present a valuable opportunity for a natural experiment with the potential to tell us much about language and consciousness.

Support was provided solely from institutional and/or departmental sources.

The author owns a small number of shares in Safer Sleep Ltd. (London, United Kingdom), a company that aims to improve safety during anesthesia, but this is unrelated to the topic of this letter.