The purpose of sleep and the mnemonic forms of experience

 

So we have a science story in the NYT entitled ‘The purpose of sleep is to forget’: https://www.nytimes.com/2017/02/02/science/sleep-memory-brain-forgetting.html

Catchy but maybe not as summary a title as one would want. They cite some assiduous research showing that during sleep the brain decreases synapses in some areas, an action mediated by at least one particular protein that we know of. Some of this work was done by Guilio Tononi who collaborated with Gerald Edelman before his death. What a lot of good science is being done. The premise underlying the title is that loss of synapses equals forgetting. Not so fast there, my friends. Pruning improves and sharpens growth, helping forms to be articulated more coherently, as the story goes on to explain. Sure we may forget some details due to pruning, but we also forget without pruning, and the larger purpose is to remember (and imagine) more clearly. Let me explain myself better.

The NYT title refers simply to the ongoing debate about what is sleep is for. Why sleep? We know sentience and being awake helps exploit environmental resources, e.g., food. Some think sleep keeps us quiet at night when predators are about; others think sleep lets the brain clean up metabolites and such, much like I take the compost out after cooking. Tononi and colleagues posed the hypothesis a while back that sleep lets us clear our minds of the residua of the day and prepare for another and further research has slowly begun to support such a view. Presumably the synapses that shrunk, in some areas by as much as 18%, quite a significant proportion, had enlarged dealing with the exigencies of the days past. Here is my question: does the shrinkage constitute pruning, like apoptosis, or consolidation, like items in STM moving to LTM, if you get my gist here. Remember that TMs are not spaces but activity and that activity contributes to invariant and variant mental structures (you know, of information).

Our model for pruning comes from apoptosis, the death of neurons that are poorly connected or that connect poorly during early maturation of the year or so after birth, thereby contributing to the invariances of personality through attachment and affective regulation. This pruning promotes the development of other systems and structures, reducing noise in the processes, that are presumably more adaptive to the person’s niche. Our model for consolidation is not quite so clear. It can be looked at from several perspectives. There is the long standing cognitive research tradition studying short and long term memories, how the transition between them might happen and what happens when it doesn’t happen as in the case of H.M. who had his hippocampi ablated to control epilepsy but taught us so much about the loss of that transition between STM and LTM. Neuroscience, both clinical and experimental, has long studied the processes of symbolic competence and performance, i.e., the maturation and development of language and how it is compromised by disorder and trauma (aphasias, etc.). For example, consider word retrieval. Frequently used words in your vocabulary come to mind almost effortlessly while more unusual ones are more difficult to remember. Could it be that the higher frequency usage keeps the memory traces of neurons and synapses primed while pruning leaves less frequently used words less accessible?

Consider as well the connectome, that ongoing connective patterning of CNS communication amongst its systems, and the clinical example of a young scientist falling into icy water who died, whose body was recovered after some time underwater, and who was later resuscitated at a hospital, her identity intact and who with therapy came back close to her previous self and competence. Somehow her connectome was resilient and unpruned or at least, information not forgotten and lost.  Next consider the question of how dreaming plays into synaptic flux. Do synapses shrink or grow or just maintain with dreaming? And what about meditation? How does this pruning/consolidation change with developing expertise at meditation?

My list goes on, a sort of wish list for empirical clarification. When someone is depressed and their cognition is a maladaptive redundant feedback loop called rumination, what happens to their synaptic tidal rhythms? Does cognitive therapy bolster both the ebbing of ruminative circuits and their replacement with the flow of adaptive flexible and realistic cognition? Does this tidal flow while sleeping contribute to that? When someone cogitates over a problem like Monod’s colleague, Jakob Wolff, who subconsciously solved a problem leading to our understanding of rDNA, how does the brain keep the thought processes alive when asleep, as with Kekule’s dream of the benzene ring or Wolff’s insight flash during a movie with his wife? (She did indeed, I hope, understand why they had to leave the theatre and return to his desk). Did the cogitations over a theoretical problem keep certain thoughts bright and let others dim, thereby heightening and clarifying the gestalt answering the theoretical call?

This is already a longer post for me (and I have much else to do today), so let me not go into a lot more details of which there are many, and instead go back to my notion that sentience and consciousness are quite different. In my thinking sentience is a basic life function; the sensing of the environment is necessary to solve the world problem of finding nutrients and conspecifics and avoiding the bad stuff. The evolution of sentience, then, can be traced from early single celled organisms to multicellular ones and then through its evolutionary victory with vertebrates, especially mammals. When we think of an animal’s Umvelt, we usually think of its sentient abilities. Consciousness is the contribution of the organism’s own autogenic impulses to its Umvelt; consciousness is the suffusion of information from memory and imagination to sentience. I have talked about this many times in past posts, like when I say we can be +/-sentient and +/-conscious, creating a 4 celled matrix:

SENTIENCE/CONSCIOUS            + sentient                                  -sentient

+conscious                                       awake                                              dream (REM sleep)

-conscious                                       hypnosis/dissociative                    sleep (slow wave)

I have also discussed this in reference to Jaak Panksepp’s remarkable observation that the center for dreaming (REM) seems to have appeared in evolution before the centers for arousal/awake. Thus, looking at this in a poetic light, animals dreamed before they awoke. (Actually the earlier dream centers controlled arousal through the suffusion of conscious energy into sentient processes. With further evolution sentient processes gained their own arousal governance system, I presume because of the increasing scope and power of perceptual abilities, e.g., olfactory, auditory, and visual and the special systems for conspecific recognition and interaction and consciousness increased in its power to manage memory and imagination.)

Here’s my point now: The research into the tidal ebb and flow of synapses during sleep does not reveal that the purpose of sleep is forgetting, though that is part of it, but it does provide a glimpse into how sentience and consciousness interact in a balanced manner, of how they are balanced. This is a dialectical process by which the organism’s vital nerve centers incipient to its intentional stance exert control over and respond to the sentient processes that are necessary for adaptive functioning. Unconscious sentience is mechanical and inflexible. Insentient consciousness is fluid with a reality unbounded by necessities though fertile with possibilities. Conscious sentience, when balanced, allows creative intelligence to flourish, and some of that balancing occurs when unconscious insentience allows the chaff of the days to be separated from the seeds needed for the next mental crop.

So remember, please, as you travel on, where you read such thoughts first put together. I will pause and dream about variant and invariant forms in language and art, in memes and tropes, and how each aesthetic communication transmits an organized form of experience allowing it to be replicated in another mind and how this organization leads to mobilization. Right on.

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