Where We Stand in Understanding Consciousness

Many scientists, even physical scientists, assert that the Holy Grail of science is to understand human consciousness. This human state is even hard to define, but is characterized by a state in which we know what we believe, know, and imagine, know what we decide and plan, and feel what we feel. That explains nothing.

The problem in understanding is not only that the mechanisms must surely be complicated, but also that we don’t have good non-invasive experimental tools. There are only two useful tools, a metabolic proxy of neural electrical activity (functional fMRI) and scalp monitoring of electrical activity (the electroencephalogram {EEG), or its magnetic field counterpart. Among the problems with fMRI are that it is only an indirect measure of the actual signaling within the brain that generates thought and feeling and enables consciousness. Its time resolution is about one-second or more, whereas signaling in the brain occurs on a millisecond scale. Although the EEG monitors activity on the appropriate time scale, it has very poor spatial resolution, inasmuch as voltage fields over various regions of cortex overlap, because the voltage extends in progressively diminished amplitude throughout the conductive medium of brain from its source of generation to other source generators. Although the EEG does monitor the appropriate target (electrical activity), that activity is an envelope of the algebraically summed signals from heterogeneous neuronal ensembles, which are nerve impulses and their associated postsynaptic potentials nearest the sensing electrodes.

                                             By Davidboyashi - Own work, CC BY-SA 4.0

Nonetheless, we do know many useful things about brain function that are surely involved in conscious functioning. Neuroscientists have discovered much of this in lower animals from invasive procedures that are not permissible in humans. In summary, we can list the following brain functions that are relevant to consciousness:

• The brain is a network of richly inter-connected networks.
• Functions are modular. Different networks have different and shifting primary functions, and some may be selectively recruited when their function is needed.
•  Some networks can perform multiple functions, depending on which other networks have recruited them into action.
• Some aspects of functional connectivity of different networks differ in unconscious and conscious states.
• Wakefulness and consciousness are not the same. Wakefulness is necessary but not sufficient for consciousness.
•  A great deal has been learned about the neural mechanisms causing wakefulness but that has not helped much in understanding consciousness.
• The messaging signals of brain are nerve impulses and their neurotransmitter postsynaptic effects.
• The summed voltages of the messaging have electrostatic effects that alter the excitability of the neurons within the voltage field.
• The frequency of bursts of impulses and their EEG envelope impose important effects on gating and throughput of information as it propagates and is modified throughout the global workspace of networks.
• There are multiple neural correlates of consciousness, but we have not identified with certainty which ones are necessary and sufficient for consciousness.

Oscillatory electrical activity is thought to have a key role in selective routing of information in the brain. Oscillations seem to modulate excitability, depending on phase relationships of linked neuronal ensembles. Two prominent hypotheses have been advanced as crucial for consciousness, and they are not mutually exclusive:

• Phase-locked activity in two or more ensembles (coherence)
• Inhibitory gating that directs pathways for propagation within networks.

The key to discovering mechanisms of consciousness is to identify all the neural correlates and then winnow the list to those that are both necessary and sufficient for consciousness. Sometimes, important discoveries occur when you study the opposite of what you want to study. This principle is manifest in studies on brain function during various states of unconsciousness (like anesthesia, coma, or non-dream sleep). A recent review of research compared the neural correlates of unconsciousness with those of consciousness. The evaluation showed disrupted connectivity in the brain and greater modularity during unconscious state, which inhibited the efficient integration of information required during consciousness. Additionally, the review made the key point that the neural correlates of consciousness that matter are the ones that occur in consciousness but not in unconscious states. Of particular relevance are the correlates related to functional connectivity among networks, because multiple lines of evidence reveal that this connectivity degrades during unconscious states and returns when consciousness resumes.

In rodents, multi-array recordings in visual cortex indicate that connectivity patterns are the same during anesthesia as in wakefulness. Perhaps this indicates that rodents do not have the needed network architecture to enable consciousness. They can be awake but not conscious. Being awake is clearly necessary for consciousness, but not sufficient. In addition (if you don’t believe me, see the classical U-tube basketball-game video on inattentional blindness). At any given instant, we are only consciously aware of the specific cognitive targets to which we attend.

 Statistical co-variation of activity in linked networks is a measure of functional connectivity. The activity in linked networks may randomly jitter or be in phase or locked at certain time lags. Operationally, the connectivity may enable one group of neurons to mediate or modulate activity in another for past, present, or future operations. The temporal dynamics of these processes differ depending on the state of consciousness.

A very popular view on consciousness among neuroscientists these days is that higher-order thinking, especially conscious thinking, is mediated by extracellular voltage fields that oscillate in the range of 12 to 60  or more waves per second. Changes in oscillatory frequency and coherent coupling of the oscillations among various pools of neurons are thought to reflect the nature and intensity of thought.

The issue arises as to how these voltages, commonly called field potentials, can influence the underlying nerve impulse activity that causes the oscillation in the first place. The messages of thought are carried in patterns of nerve impulses flowing in neural networks. Field potentials are not signaling, at least  not directly. They may well indirectly influence messaging by electrostatically biasing networks to be more or less able to generate and propagate nerve impulse traffic.

Neuroscientists attach much importance to the temporal dynamics of EEG voltage frequencies. For example, at one time neuroscientists believed that 40/sec synchrony was critical to consciousness, but later studies revealed that this synchrony can be maintained and even enhanced during anesthesia. Later, investigators thought they had found a crucial role for higher frequency gamma synchrony, but that too is now called into question. This gamma synchrony can be present or even enhanced during unconsciousness. However, the spatial extent of synchrony may be the meaningful correlate of consciousness. Widespread synchrony breaks down during unconsciousness, while more localized synchrony remains intact or even enhanced.

Numerous studies show a breakdown of functional connectivity during various states of unconsciousness. For example, fMRIs reveal cortico-cortical and thalamocortical disconnections during sleep, general anesthesia, and pathological states. EEG analysis shows similar connectivity breakdowns. Additionally, the repertoire of possible connectivity configurations that can be accessed diminishes during unconscious states and is restored as consciousness resumes. This obviously limits the robustness of information processing that can occur in unconsciousness. Conscious selective attentiveness likely requires a different repertoire of connectivity than inattentive consciousness.

Neuroscientists are also discovering the importance not only of multi-area coherence at a given frequency band, but also that the phase synchrony to two different frequencies can also modulate network communication. Cross-frequency coupling of the alpha and beta oscillations with higher frequency gamma oscillations can amplify, inhibit, or gate the flow of nerve impulses throughout circuitry.

Future advancements will surely include more emphasis on monitoring functional connectivity as the brain shifts into and out of various states of consciousness and unconsciousness. I think, however, that we will not make definitive progress in consciousness research until we make progress in one area of theory and another of tactical methodology.

The theory deficiency lies in models of neural networks. Computer models of man-made networks yield interesting results, but they are probably  not relevant. Brains do not work with the same principles that computers do. Moreover, brain networks have intrinsic plasticity that cannot yet be duplicated by computers.

The method deficiency is that we have no non-invasive way to monitor the actually signaling in even a significant fraction of all the neurons in all the networks. Moreover, even if we had a way to monitor individual neurons noninvasively, it would likely be necessary to selectively monitor neurons in defined circuits. Ultimately, we may confirm that some things are just not knowable. Surely, however, we can learn more than we do now.

Sources:

Bonnefond, Mathilde et al. (2017). Communication between brain areas base on nested oscillators. eNeuro. 10 March. 4(2) ENEURO.0153-16.2017. doi: https://doi.org/101523/ENEURO.0153-16.2017.

Mashour, George A., and Hudetz, Anthony G. (2018). Neural correlates of unconsciousness in large-scale brain networks. Trends in Neurosciences. 41(3), 150-160.

Cursive Writing Makes Kids Smarter

Ever try to read your physician’s prescriptions? Children increasingly print their writing because they don’t know cursive or theirs is unreadable. I have a middle-school grandson who has trouble reading his own cursive. Grandparents may find that their grandchildren can’t read the notes they send. Our new U.S. Secretary of the Treasury can’t (or won’t) write his own name on the new money being printed.

When we adults went to school, one of the first things we learned was how to write the alphabet, in caps and lower case, and then to hand-write words, sentences, paragraphs, and essays. Some of us were lucky enough to have penmanship class where we learned how to make our writing pretty and readable. Today, keyboarding is in, the Common Core Standards no longer require elementary students to learn cursive, and some schools are dropping the teaching of cursive, dismissing it as an “ancient skill.”[1]

The primary schools that teach handwriting spend only just over an hour a week, according to Zaner-Bloser Inc., one of the nation's largest handwriting-curriculum publishers. Cursive is not generally taught after the third grade (my penmanship class was in the 7^th grade; maybe its just coincidence, but the 7^th grade was when I was magically transformed from a poor student into an exceptional student).

Yet scientists are discovering that learning cursive is an important tool for cognitive development, particularly in training the brain to learn “functional specialization,”[2] that is capacity for optimal efficiency. In the case of learning cursive writing, the brain develops functional specialization that integrates both sensation, movement control, and thinking. Brain imaging studies reveal that multiple areas of brain become co-activated during learning of cursive writing of pseudo-letters, as opposed to typing or just visual practice.

There is spill-over benefit for thinking skills used in reading and writing. To write legible cursive, fine motor control is needed over the fingers. Students have to pay attention and think about what and how they are doing. They have to practice. Brain imaging studies show that cursive activates areas of the brain that are not affected by keyboarding.

Much of the benefit of cursive writing comes simply from the self-generated mechanics of hand- printing letters. During one study at Indiana University to be published this year,[3] researchers conducted brain scans on pre-literate 5-year olds before and after receiving different letter-learning instruction. In children who had practiced self-generated printing by hand, the neural activity was far more enhanced and "adult-like" than in those who had simply looked at letters. The brain’s “reading circuit” of linked regions that are activated during reading was activated during cursive writing, but not during typing. This lab has also demonstrated that writing letters in meaningful context, as opposed to just writing them as drawing objects, produced much more robust activation of many areas in both hemispheres.

In learning to write by hand, even if it is just printing, a child’s brain must:

•            Locate each stroke relative to other strokes.
•            Learn and remember appropriate size, slant of global form, and feature detail characteristic of each letter.
•       Develop categorization skills.

Cursive writing, compared to printing, is even more beneficial because the movement tasks are more demanding, the letters are less stereotypical, and the visual recognition requirements create a broader repertoire of letter representation. Cursive is also faster and more likely to engage students by providing a better sense of personal style and ownership.

Other research highlights the hand's unique relationship with the brain when it comes to composing thoughts and ideas. Virginia Berninger, a professor at the University of Washington, reported her study of children in grades two, four and six that revealed they wrote more words, faster, and expressed more ideas when writing essays by hand versus with a keyboard.[4]

There is a whole field of research known as “haptics,” which includes the interactions of touch, hand movements, and brain function.[5] Cursive writing helps train the brain to integrate visual, and tactile information, and fine motor dexterity. School systems, driven by ill-informed ideologues and federal mandate, are becoming obsessed with testing knowledge at the expense of training kids to develop better capacity for acquiring knowledge.

The benefits to brain development are similar to what you get with learning to play a musical instrument. Not everybody can afford music lessons, but everybody has access to pencil and paper. Not everybody can afford a computer for their kids−maybe such kids are not as deprived as we would think.

Take heart. Some schools just celebrated National Handwriting Day on Jan. 23. Cursive is not dead yet. Parents need to insist that cursive be maintained in their local school.

Readers who want an easy way to acquire a neuroscience background will want to know about the 2nd Edition of my e-book, “Core Ideas in Neuroscience.” Check my web site for available formats and sources (thankyoubrain.com/neurobook). Also check out the Neuro-education discussion group I just created on Linkedin (type “Neuro-education" in Linkedin’s search field).

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[1] Slape, L. “Cursive Giving Way to Other Pursuits as Educators Debate Its Value.” The Daily News, Feb. 4,

2012. http://tdn.com/news/local/cursive-giving-way-to-other-pursuits-as-educators-debate-its/article_c0302938-4f94-11e1-af3a-0019bb2963f4.html

[2] James, Karin H. an Atwood, Thea P. (2009).The role of sensorimotor learning in the perception of letter-like forms: Tracking the causes of neural specialization for letters. Cognitive Neuropsychology.26 (1), 91-100.

[3] James, K.H. and Engelhardt, L. (2013). The effects of handwriting experience on functional brain

development in pre-literate children. Trends in Neuroscience and Education. Article in press.

[4] Berninger, V. “Evidence-Based, Developmentally Appropriate Writing Skills K–5: Teaching the

Orthographic Loop of Working Memory to Write Letters So Developing Writers Can Spell Words

and Express Ideas.” Presented at Handwriting in the 21st Century?: An Educational Summit,

Washington, D.C., January 23, 2012.

[5] Mangen, A., and Velay, J. –L. (2010). Digitizing literacy: reflections on the haptics of writing. In Advances in Haptics, edited by M. H. Zadeh. http://www.intechopen.com/books/advances-in-haptics/digitizing-literacy-reflections-on-the-haptics-of-writing

Is Lack of Sleep Causing Your Brain to Shrivel?

Snore a lot? Get up frequently at night to urinate? Wake up at 2 A.M. with bright ideas or worries? All these disruptions of sleep are common and more so as we get older. Does it matter? Well, of course such awakenings disrupt our sleep, and maybe it is just inconvenient. But disrupted sleep not only is more likely with age, it may promote deterioration in mental functioning. A recent study compared the effects of sleeping behavior in young adults and seniors. The study involved assessing the memory after sleeping of 18 young adults in their 20s and 15 older adults in their 70s. The subjects were tested on 120 word sets before they went to bed, and an EEG machine monitored their brain activity while they slept. Upon awakening, they were tested once again on the word pairs, but this time they took the tests while undergoing functional  magnetic resonance imaging (fMRI) scans.

The quality of deep sleep among the older adults was 75 percent lower than the younger ones, and their memory was significantly worse the next day−55 percent worse. The scans suggested deterioration of the frontal lobe. Shrunken brains can occur from aging and shrunken brains impair thinking and memory. But is it possible we have the cause and the effect backwards. Maybe what happens in the environment, such as impaired sleeping, causes both the shrunken brain and the impaired memory. Or in other words, what causes older brains to shrink?

Scientists consider a decrease of about 2% shrinkage every 10 years as normal. That may not be normal, just what most people experience because they are not taking care of their brains. There is abundant research that shows that exercises for both the brain and body help to reduce brain atrophy.

Of course, anything that damages neurons can reduce the number of their tree-like processes and the density of their contact points with other neurons. The list of such causes is long, including: alcohol abuse, brain inflammation, certain infections, concussion, impaired blood supply, lack of intellectual stimulus, vitamin B12 deficiency. It now appears that we should add fragmented sleep to the list.

Common natural causes of fragmented sleep in older humans are alcohol abuse and sleep apnea. Also, in males, enlarged prostate causes a need for frequent urination. As I have explained in my learning and memory blog posts (thankyoubrain.blogspot.com), learning events during the day are consolidated into lasting form during the sleep at night of the same day. We don’t know exactly how sleep helps, but obviously, you have far fewer mental distractions during sleep — unless, of course you keep waking up.

Alzheimer’s Disease also causes fragmented sleep. So, it is no surprise that the brain degeneration by the disease would cause memory problems. But maybe, just maybe, it is the fragmented sleep that accelerates onset of Alzheimer’s disease. Now, this seemingly ridiculous possibility has to be taken seriously in light of new research showing that sleep-disordered breathing, as in sleep apnea, seems to increase the risk of mental decline and even dementia in older women.

Disrupted sleep may also accelerate normal aging. This is certainly true when the cause is sleep apnea, which raises blood pressure and increases the cardiovascular damage that high blood pressure causes. Blood clotting is promoted, increasing the likelihood of strokes. Obesity and diabetes are often associated with sleep apnea, and it seems that sleep apnea not only results from obesity but can promote obesity and the diabetes that often accompanies obesity. Diabetes is toxic for nerve terminals. Similar neuropathy may also be occurring in their brain. Sleep apnea causes daytime sleepiness, and that it turn reduces attentiveness and mental activity, which when sustained over many years reduces the mental stimulus and promotes atrophy of neuronal processes.

Obviously, blood oxygen drops during sleep apnea. Normally, blood is 94% to 98% saturated with oxygen. But not breathing for 30 seconds or more during sleep causes oxygen level to drop to 80% or less. Any level below 90% oxygen level is dangerous, especially to the brain which demands nearly 20% of all the body’s oxygen supply. The adult brain can only survive about four minutes once oxygen is completely cut off.

So it is entirely possible that the slipping memory we see in so many elderly is a warning sign of something much more serious. But by the time the memory deficits show up, much of the damage has already been done. Prevention is the best hope.

Source:

Mander, B. A., Rao, V.,  Brandon, B. L., Saletin, J. M.,  et al. (2013). Prefrontal atrophy, disrupted NREM slow waves and impaired hippocampal-dependent memory in aging. Nature Neuroscience  doi:10.1038/nn.3324 

http://www.livestrong.com/article/161959-what-are-the-causes-of-brain-atrophy/

Yaffe, K., Laffan, A. M., Harrison, S. L. et al. (2011). Sleep-disordered breathing, hyupoxia, and risk of mild cognitive impairment and dementia in older women. JAMA. 306 (6), 613-619. doi:10.1001/jama.2011.1115

For those who want to learn more about the brain, Dr. Klemm has just released the second edition of his e-book, “Core Ideas in Neuroscience.” See http://thankyoubrain.com/neurobook/index.htm