Reply: Response to 'Minimally conscious state or cortically mediated state?'

Sir, In a recent review ‘Minimally conscious state or cortically mediated state?’ Naccache argues that the minimally conscious state (MCS) should be relabelled the ‘cortically mediated state (CMS)’ (Naccache, 2017). Naccache motivates this change of nomenclature by arguing that the criteria associated with the MCS ‘do not inform us about the potential residual consciousness of patients, but they do inform us with certainty about the presence of a cortically mediated state’. We begin by addressing Naccache’s positive proposal before turning to his criticisms of the MCS. Naccache is certainly right to claim that the MCS criteria do inform us with certainty about the presence of a CMS. However, this fact alone does not justify the rebranding exercise that he recommends. (After all, the criteria associated with the MCS also inform us with certainty that the patient is still alive, but no-one would suggest that the MCS should be relabelled the ‘Still Alive State’.) Further, there are two very good reasons for not adopting Naccache’s proposed new label. First, this label fails to preserve the distinction between MCS patients and patients who have ‘emerged’ or ‘exited’ from the MCS (EMCS), for the behaviours associated with EMCS patients are also cortically mediated. Indeed, Naccache’s proposal threatens to elide the contrast between MCS patients and neurotypical individuals. Second, Naccache’s proposed terminology fails to engage with the concerns of families and caregivers in the way that the current terminology does. Care-givers and family members are not interested in whether the patient’s behaviours are cortically mediated; instead, they want to know whether these behaviours are accompanied by experiences (and if so, what those experiences are like). They want to know whether the patient is ‘minimally conscious’, or whether s/he is ‘merely vegetative’ and lacks any capacity for consciousness. The diagnostic categories that we use in this domain ought to engage with these concerns rather than avoid them (as Naccache’s proposed categories do). The fact that clinicians might describe a patient as being in a ‘cortically mediated state’ is unlikely to dissuade family members from asking whether s/he is conscious. We turn now to Naccache’s claim that the criteria currently associated with the MCS ‘do not inform us about the potential residual consciousness of patients’. At the heart of Naccache’s worry is what he refers to as the ‘paradoxical’ practice of attempting to infer consciousness in patients who are unable to report their experiences. Naccache regards this practice as ‘paradoxical’ because he thinks that consciousness can be ‘defined’ as the ability to self-report. But there is no genuine paradox here at all. Theorists are obviously at liberty to define ‘consciousness’ as they wish, but definitions of ‘consciousness’ are of interest only insofar as they capture our pre-theoretical conception of consciousness. It is evident that we have a concept of consciousness that is not defined in terms of the capacity for subjective report, for it is an open question whether infants, braindamaged patients and non-human animals have unreportable experiences. (If consciousness were defined in terms of reportability then this would not be an open question.) Naccache also claims that the reportability definition of consciousness is ‘very close’ to the neurological definition of consciousness provided by Plum and Posner (1972): ‘Consciousness means awareness of self and environment’. However, awareness and reportability should be sharply distinguished. A lioness might be aware of the prey that she is stalking, but she presumably lacks the capacity to doi:10.1093/brain/awy023 BRAIN 2018: Page 1 of 2 | e1