Misunderstanding Sleep: And, so, Misunderstanding how we Attend when Awake

napping-neuronsWhile we are quite interested in noting that these researchers have detected this exceedingly subtle phenomenon, we suspect that their interpretation of their findings is exceedingly superficial.

No, we don’t have research results to the contrary, but our intution tells us that they are truly missing the ultimate signficance of their findings and that they are “stuck” in an outdated and cliched view of “sleep” itself.

What they have uncovered is not some odd “anthropomorphizing” melodrama about the neurons being so tired from alll their hard work that they need to take a nap to refresh themselves for their next task or demand from the environment. That is truly bordering on the laughable to us. (Sorry but we just have never been very politically correct).

In philosophical discussion, this kind of “error” in logic is called the “merological” fallacy. It is clear that just because the pattern of frequencies and waves is analogous to the pattern that occurs at night when we are sleeping in those nonREM periods, THAT does not at all imply that the “neurons” are themselves tired and need a nap and are therefore “sleeping’!!!!! Wow!

As to the findings here, there is a well-known correlation between arousal and neuronal activity in the brain. However, it is unclear how these general effects are reflected on a local scale.

Engel et al. recorded from higher visual areas in behaving monkeys and discovered a new principle of cortical state fluctuations.

In the past, people had known that individual neurons go through phases of being more or less active, but with this probe they saw for the first time that all the neurons in a given column cycled together between firing very rapidly then firing at a much slower rate, similar to coordinated cycles in sleep.

“Selective attention is similar to making small parts of your brain a little bit more awake,

When we are in a deep slumber our brain’s activity ebbs and flows in big, obvious waves, like watching a tide of human bodies rise up and sit down around a sports stadium. It’s hard to miss.

During slow-wave sleep and anesthesia, ensem- ble neural activity exhibits slow synchronous transitions between periods of high activity and quiescence. In individual neurons, these tran- sitions manifest as alternating Down (hyper- polarized) and Up (depolarized) phases of the membrane potential due to, respectively, an ebb and flow of synaptic activity . In awake animals, these slow synchronous transitions are less frequent, and thus, ensemble neural activity appears less synchronized than during anesthe- sia or slow-wave sleep

Stanford researchers have found, those same cycles exist in wake as in sleep, but with only small sections sitting and standing in unison rather than the entire stadium. It’s as if tiny portions of the brain are independently falling asleep and waking back up all the time.

The On and Off episodes resembled the Up and Down phases commonly observed during anesthesia and slow- wave sleep and were consistent with the large fluctuations in cortical membrane potentials rec- orded intracellularly in behaving monkeys

What’s more, it appears that when the neurons have cycled into the more active, or “on,” state they are better at responding to the world. The neurons also spend more time in the on state when paying attention to a task. This finding suggests processes that regulate brain activity in sleep might also play a role in attention.

The outcomes indicate that On-Off dy- namics are locally and selectively modulated within confined retinotopic regions and do not
solely reflect a global arousal state.

http://neurosciencenews.com/brain-sleep-neuroscience-5652/

Their data revealed that the state changes affected neuronal excitability across all layers of the neocortex. They found that ensemble neural activity in primate visual cortex spontaneously fluctuated between phases of vigorous (On) and faint (Off) spiking synchronously across cortical layers.

Those cycles, which occur on the order of seconds or fractions of seconds, weren’t as visible when awake because the wave doesn’t propagate much beyond that column, unlike in sleep when the wave spreads across almost the entire brain and is easy to detect.

These On-Off dynamics, reflecting global changes in cortical state, were also modulated at a local scale during selective attention.

When the team gave a cue to where a change might occur, the neurons within the column that senses that part of the world all began spending more time in the active state.

In essence, they all continued flipping between states in unison, but they spent more time in the active state if they were paying attention

When the animals attended to a stimulus, the vigorous spiking states became longer and the faint spiking states became shorter.

Our results suggest that global mechanisms governing cortical states may them- selves also operate on a local scale or, alterna- tively, may interact with separate attentional control mechanisms operating locally.

http://science.sciencemag.org/content/354/6316/1140

The Rest of the Story:

While we are quite interested in noting that these researchers have detected this exceedingly subtle phenomenon, we suspect that their interpretation of their findings is exceedingly superficial.

No, we don’t have research results to the contrary, but our intution tells us that they are truly missing the ultimate signficance of their findings and that they are “stuck” in an outdated and cliched view of “sleep” itself.

So, here’s what the paparazzi say, for example,”It’s as if tiny portions of the brain are independently falling asleep and waking back up all the time.”…Truly a bit of melodrama here that invokes a view of sleep thats about 100 years old.

The authors of the reseach themselves, lapse into this idea of ‘sleep’ as an event based on an exhaustion and replenishing of energy being required.

A question that comes out of this work is why the neurons cycle into a lower activity state when we’re awake. Why not just stay in the more active state all the time in case that’s when the saber tooth tiger attacks?

One answer could relate to energy. “There is a metabolic cost associated with neurons firing all the time,” Boahen said. The brain uses a lot of energy and maybe giving the cells a chance to do the energetic equivalent of sitting down allows the brain to save energy.

Also, when neurons are very active they generate cellular byproducts that can damage the cells. Engel pointed out that the low-activity states could allow time to clear out this neuronal waste.

However, it seems to us…that what is missing here is the critical point that Slow Wave Sleep and its characteristic activity is a basic essential to the ongoing development of our cognitive processes and our ability to learn from experience.

Ir ia not an intermittent exhaustion and shut down of “the awake state”..a key aspect of the way our ‘minding brain” goes about “mind”-ing..

Short-term memory of events is stored in an area of the brain called the hippocampus. Long-term memories, however, are encoded in the neocortex. The transfer of memories from the hippocampus to the neocortex is called memory consolidation, and happens while we sleep.

Intracellular recordings indicate that sleep slow waves reflect a bistability of cortical neurons undergoing a slow oscillation (<1 Hz) between two distinct states, each lasting hundreds of milliseconds.

Regional Slow Waves and Spindles in Human Sleep

http://dx.doi.org/10.1016/j.neuron.2011.02.043

Up states are associated with depolarization and vigorous firing, whereas in down states, the membrane potential is hyperpolarized and neuronal firing fades  Although a role has been suggested for thalamic oscillators , the slow oscillation can be generated and sustained in cerebral cortex alone

This, after all, is what the recent explosion of findings having to do with “consolidation” of memory during the slow wave sleep stage directly implicates.

At one extreme, typical of early NREM sleep, high-amplitude slow waves were usually global, detectable with scalp EEG. At the other extreme, more typical of late NREM sleep, slow waves could be entirely local, where any region could be active or inactive.

In addition, we find that sleep spindles—the other EEG hallmark of NREM sleep—also occur mostly locally, establishing that the two fundamental sleep oscillations are mostly confined to local circuits.

There is also a robust tendency of sleep slow waves to propagate from medial prefrontal cortex to the medial temporal lobe (MTL) and hippocampus.

In other words, what goes on during that stage…and then the subsequent REM stage which must deal with the consequencdes of the consolidating interactions between the hippocampus and cortex appears to be the basis of learning from events in our experience and the alteration of our neural patterning and connectivity as a result of those moments.

Memory consolidation is a process whereby new memories are integrated into a pre-existing stable network of long-term associations

Consolidation is strongest during ‘off-line’ periods when there is no interference from new encoding-such as during sleep  Several studies report the importance of slow wave sleep (SWS) in the consolidation of declarative, consciously accessible memories

It is believed that during SWS, slow oscillations temporally coordinate hippocampal and thalamic brain activity during the depolarizing up-state of the oscillation.

This hippocampal-neocortical dialog is thought to underly the transfer of information between brain structures and their memory systems .This very same “consolidation” process actually occurs during the brief naps that many of us experience during the day…

Cross-hemispheric Alternating Current Stimulation During a Nap Disrupts Slow Wave Activity and Associated Memory Consolidation

DOI: http://dx.doi.org/10.1016/j.brs.2014.12.010

Scientists had long believed that each sleep spindle oscillation peaked at the same time everywhere in the neocortex of the brain. But even at night the phenomenon does occur in such a manner that it appears differently in differnent neuronal assemblies however, the sleep spindles weren’t peaking simultaneously everywhere in the cortex.  Instead, the oscillations were sweeping in circular patterns around and around the neocortex, peaking in one area, and then—a few milliseconds later—an adjacent area.

. It is now thought that this type of cycling over different regions of the brain and the resulting  organization is letting neurons talk to neurons in other areas,” says Muller. “The time scale that these waves travel at is the same speed it takes for neurons to communicate with each other.”

Rotating waves during human sleep spindles organize global patterns of activity that repeat precisely through the night

https://elifesciences.org/content/5/e17267/article-metrics

However, when we read the consolidation research and marval at how vital the SWS periods are to learning, the question immediately arises and has arisen for many of the authors:  Surely we can benefit from the moments of our lives in a more immediate fashion and not have to wait to go to sleep that night in order to the impact of the waking moment to have made itself felt in our neural structuring and the networks associated with it.

What happens when events duirng the day lead to consequences within the next hours or even minutes…and these conseuqences are more than fleeting.

It appears that this finding of these ongoing, previously undetected events during attemtion processes may indeed be the clue to the answering of this question.

What these researchers see is not some odd “anthropomorphizing” fairy tale about the neurons being so tired from alll their hard work that they need to take a nap to refresh themselves for their next task or demand from the environment. That is truly bordering on the laughable to us. (Sorry but we just have never been very politically correct).

In philosophical discussion, this kind of “error” in logic is called the “merological” fallacy. It is clear that just because the pattern of frequencies and waves is analogous to the pattern that occurs at night when we are sleeping in those nonREM periods, THAT does not at all imply that the “neurons” are themselves “sleeping’!!!!! Wow!

On the contrary, if we see these characteristics of what occurs in SlowWaveSleep during our nights reemerging on a more covert and sleeting basis while we are actually engaged in tasks which are essentially “life and death” evolutionarily in terms of ‘lessons being learned” and the consolidation and integration of those experiences into the ongoing structures of thought…then clearly this “sleeping’ is NOT at all just sleeping. But should be looked at as a key, a crucial key to how our minds work and integrate experience during the day time…

and really lets not forget that we do spend about 70% of our time awake…and we better have mechanisms, albeit likely similar mechanisms for “consolidating “memory during those hours as well.

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