Does our consciousness die when we go to sleep or fall into a coma? I have sometimes wondered if our consciousness dies when we go to sleep at night or perhaps when we enter a deep coma, like from brain damage, for example.  When we wake, or are woken, a new consciousness is booted up with the memories of the previous consciousness, so that it gives the illusion of one continuous consciousness.   This question may be partly philosophical as well as scientific, because it looks at some of the assumptions about the nature of consciousness.

A possibly unfair analogy might be to a computer, when its running it has a memory-set like a consciousness.  And if you shutdown and reboot the computer, then it can continue running as it did before, as if it had never been shut down.  However, once a computer is shut down, its largely inert, though I know there are unimportant edge cases exceptions to this.  The computer is effectively dead when its shut down, its ram has largely dispersed.  We can start the computer back up, but it will really be loading the ram from disk.  The original electrical activity that made up the 'consciousness' of the computer before it was rebooted is effectively dead.

How do we know we don't die when we go to sleep? I mean even if our consciousness doesn't wholly die, we may suffer a partial death of sorts. I could be wrong, but I believe its possible for victims of brain damage to show minimal neural activity.  Rarely, but occasionally some of these victims recover, but perhaps their brain has rebooted their mental ram (if you will). And they may not technically be the same consciousness who fell into the coma, but merely a copy of that consciousness reconstituted from data held in the brain.

Surely plenty have considered this question, has there been any research?  Do we have any kind of answer to this question?
Q: Does our consciousness die when we go to sleep or fall into a coma?

A: No, neuroscientifically speaking, the consciousness does not die when we are sleeping or are in a coma; it is just in a sleep mode or in a severely depressed mode. This is because the group of neural circuits that function to create consciousness (ref 1, 2, 3) does not die when we are in those conditions; it is just functioning in the mentioned modes, which are different from the mode when we are fully conscious. This is unlike the case when one actually dies or when one has a brain death. In such cases, this group of neural circuits actually dies. So, neuroscientifically speaking, the consciousness that comes from the function of this group of neural circuits dies too.

(Philosophically speaking, this question may be answered differently, depending on what one means by the word “die”, which can be different among different philosophers. But this is a neuroscience forum, so I won’t get into that discussion and use the word “die” in the neuroscientific sense.)

It should also be noted that consciousness is not an all-or-none phenomenon but is a graded phenomenon. There can be graded different levels of consciousness, such as (from high to low) heightened alertness, normal alertness, drowsiness, sleeping (from light to deep), stupor, and coma, depending on the stimulation/facilitation of the consciousness neural circuits from the ARAS (ascending reticular activating system, which arises from the rostral brainstem)(ref 4,5), and the ARAS stimulation can be affected by stimulants, physiological diurnal sleep-wake cycle, depressants, and various pathological conditions (such as trauma, brainstem hemorrhage, and tumor). Also, even if a person is/appears alert,  there can be graded different consciousness states in that person. These different consciousness states have different consciousness content, such as normal conscious awareness, confusion, akinetic mutism, minimally conscious state (MCS), and vegetative state (VS), depending on the severity of damages to the consciousness neural circuits, which can be affected by similar pharmacological and pathological causes just mentioned. In these conditions, patients may appear alert (i.e, opening eyes, blinking, and chewing spontaneously) but have abnormal content of consciousness (deranged in confusion, retarded in akinetic mutism, minimal in MCS, and none or almost none in VS).(ref 6,7)

So, consciousness during sleep or coma is just consciousness in one of these various physiological/pathological states. And, as long as the consciousness neural circuits are still functioning, albeit in an abnormal mode, and living, it can be considered that, neuroscientifically, consciousness is still living too (albeit in an abnormal mode).

Q: When we wake, or are woken, a new consciousness is booted up with the memories of the previous consciousness, so that it gives the illusion of one continuous consciousness. …

I could be wrong, but I believe its possible for victims of brain damage to show minimal neural activity. Rarely, but occasionally some of these victims recover, but perhaps their brain has rebooted their mental ram (if you will). And they may not technically be the same consciousness who fell into the coma, but merely a copy of that consciousness reconstituted from data held in the brain.

A: You are right. And actually, technically speaking, our present-moment consciousness is just a slightly different copy of the previous-moment one. Our brain cells are in continuous metabolic activities, which continually change both their structural components and functional components. So, technically speaking, we this moment are a biologically different entity from we a moment ago. It’s been always like this since we’re born. Yet, we feel that we are the same person with same consciousness and the same “self” all along. 

It can be argued that this feeling of same consciousness and same “self” is an evolved function to enhance the survival of an organism that has this feeling. Theoretically,  comparing two types of animals, one with this sense, and the other without this sense, with all other things identical, the one with this sense obviously has more drive to avoid danger, to seek happiness, to stay alive, and to procreate (all for the sake of its "self") than the one without this sense. So, it is logical to conclude that the sense of same consciousness and same “self” is just the evolved function to help increase the survival chance of the being and the species that possess it. (more detailed discussion in ref 8, 9)

References:


Koch C, Massimini M, Boly M, Tononi G. Neural correlates of consciousness: progress and problems. Nature Reviews Neuroscience. 2016;17: 307-321. The full pdf file can be downloaded from here.
Song X, Tang X. An extended theory of global workspace of consciousness.
Progress in Natural Science. 2008 Jul;18(7):789–793. 
Ukachoke C. Chapter 6 – Consciousness.  In: The Basic Theory of the Mind. 1st ed, 2018. p 8-18. Charansanitwong Printing Co. Bangkok, Thailand.
Yeo SS, Chang PH, Jang SH. The ascending reticular activating system from pontine reticular formation to the thalamus in the human brain. Front Hum Neurosci. 2013;7: 416. 
Wikipedia. Function of the ARAS 
Bernat JL. Chronic disorders of consciousness. Lancet 2006;367:1181–1192. 
Cavanna AE, Cavanna SL, Servo S, Monaco F. The neural correlates of impaired consciousness in coma and unresponsive states. Discov Med. 2010 May;9(48):431-438. 
Fabbro F, Aglioti SM,Bergamasco M,Clarici A,Panksepp J. Evolutionary aspects of self- and world consciousness in vertebrates. Front Hum Neurosci 2015; 9: 157.  doi: 10.3389/fnhum.2015.00157
Ukachoke C. Chapter 11 Self. The Basic Theory of the Mind. 2018.