Table 1.

Operational classification of phenomenological consciousness states related to access consciousness and phenomenological self, and the relative contribution of wakefulness, internal awareness, and external awareness to those states. Adapted with permission from Martial and colleagues.²² NREM, non-rapid eye movement sleep; REM, rapid eye moment sleep; MCS−, minimally conscious state −, with non-linguistic signs of conscious awareness; MCS+, minimally conscious state with clear evidence of expressive language functions. ^a Patients with partially preserved cortical activity compatible with MCS but not showing any behavioural sign of conscious awareness (although cognitive-motor dissociation may exist, and appropriate cortical responses to active paradigms be present as evidenced by functional neuroimaging). ^b Reportable internal consciousness experience with features that are specific to near-death experiences (out-of-body experience,…) but not associated to a critical event potentially leading to death.

Phenomenological state		Wakefulness	Internal awareness	External awareness (connectedness)	Responsiveness to verbal command
Normal awake consciousness		++++	++++	++++	++++
General anaesthesia	Deep	0	0	0	0
	Disconnected consciousness (with dreams; e.g. ketamine anaesthesia)	0	++	0	0
	Connected consciousness episodes	++	++	++	++
Sleep	NREM sleep without dream	0	0	0	0
	NREM sleep with dreams	0	++	0	0
	REM sleep with dreams	0	+++	0	0
	REM sleep with lucid dream23	0	+++	Unknown	Possible
Severe brain injury	Coma without dreams/near-death experiences	0	0	0	0
	Coma with dreams/near-death experiences	0	0	Unknown	0
	Unresponsive wakefulness syndrome	+ (fluctuating)	0	0	0
	Minimally conscious state	+ (fluctuating)	+	+	0 (MCS−) or + (MCS+)
	Minimally conscious state or non-behavioural minimally conscious statea,24	+ (fluctuating)	Possible	Possible	0 (behaviourally, but appropriate cortical response may be present)
	Emergence from minimally conscious state	++++ (fluctuating)	++	++	+
	Locked-in syndrome	++++	++++	++++	++++
Others	Drug-induced and psychotic hallucinations	++++	++++	Variable	Variable
	Near-death experience	0	+++	Unknown	Unknown
	Near-death-like experiencesb	Variable	+++	Variable	Variable