Neuronal Plasticity – How our brain transforms itself

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A painting of a large ship amidst an unforgiving storm.

“I can’t change the direction of the wind, but I can adjust my sails to always reach my destination.” – Jimmy Dean

Index

  1. ) Introduction
  2. ) Ingrained adaptability
  3. ) Our plastic brain
  4. ) Neural utility
  5. ) Neuronal principles
  6. ) Conclusion/Related reading
  7. ) References
1) Introduction

This article will provide you with a variety of interesting facts and pieces of knowledge related to our brain’s innate restructuring mechanisms. First and foremost, you will be informed about neuronal plasticity, a process which is imperative in terms of tackling the fluidity of our existence.

Other than that, you will also be able to gain insight into how new memories are formed and how our brain manages to reorganize itself. Besides, you will also be given an in-depth overview of underlying mental processes concerning the formation of memory and a few pieces of information related to the art of learning itself.

2) Ingrained adaptability

In order to remain vigilant and thus propagate our genes into the next generation, nature has endowed us with a powerful mental faculty – namely the brain. Scientists speculate that our biological super-processor consists, on average, of about 86 billion neurons [1]. These small parts of natures’ most complex invention allow us to excel in a plethora of disciplines. Its congenital fluidity, which is commonly referred to as “neuronal plasticity”, is the reason, why humans tend to differ from each other in their everyday conductance.

Neuroplasticity poses a trait, which is not limited to human beings. All animals are capable of learning, respectively memorization – for that is, what neurons do. Yet humans appear to savor said brain-related rearrangement the most – an apparent no-brainer, given our societal flourishment.

Jordan Grafman has postulated that there are four types of neuronal plasticity [2]:

 

I) Map expansion

A compass lies on a map in an archaic style.

Our internal structure consists of a grand variety of maps.

Our brain consists of a myriad of neuronal maps, which can either increase or shrink in size. Grafman believes that the central part of a specific area of our brain encompasses the neurons, which are most committed to the task.

Neurons, which lie at the border of a given map are somewhat constantly in competition with adjacent brain regions, in terms of neuronal recruitment.

Neurons, which are not in use, will de facto give way to neurons whose services are more often needed. A somewhat eternal process (given the ongoing function of the brain, that is) of reorganization, which serves as the basis for our wildly differentiated maps.

 

II) Sensory reassignment

This type of mental reorganization occurs when one sense is no longer needed. Individuals, who have gone blind, have been shown to have undergone radical neural reconfigurations. Areas, which used to belong to visual perception, have as a consequence of the abovementioned loss of function, been reassigned to process other inputs, such as touch.

 

III) Compensatory masquerade

Our brain has many ways of approaching a given task in its repertoire. Some individuals possess an uncanny ability in the realm of spatial processing, whilst others use certain landmarks in order to navigate through a certain area. If said people were to lose their spatial abilities, they could always fall back on landmarks in order to maneuver through the environment.

Before neuronal plasticity has been recognized, this type of innate re-organization has been coined “alternative strategies”. These “strategies” have been employed to help human beings with learning disabilities – f.e. using audiotapes, insofar as accumulating knowledge goes, in homo sapiens, who are incapable of reading in a constructive manner.

 

IV) Mirror region takeover

If one area of a hemisphere fails to do its job, the mirror region in the opposite part of our brain takes over the missing mental function as best as it can.

3) Our plastic brain
Localizationism

The very thought of some kind of ingrained restructuring process was deemed absurd not too long ago. Its roots can be found in animal studies, which have been conducted in the 1950s. These precursors basically tested, whether the brains of rodents were to show a certain difference in regard to their size in relation to a given environment. Small gnawers that grew up isolated, without any sort of new input, have been compared to other small gnawers that have been exposed to a so-called enriched environment. An enriched environment basically constitutes a place, which offers all sorts of stimuli, in order to keep the mammal engaged.

A follow-up autopsy has shown a distinct differentiation in regard to not only the cortex but also the hippocampus of the mammals, which have spent their time being in an enriched environment. Said group’s brains have also shown an increase in cellular connections. [3]

It wasn’t until 1998 that the same abilities have been proven to be present in homo sapiens.

The global census before the abovementioned findings has always been in favor of “localizationism”. A term, which describes the erroneous belief that our brains are somewhat hardwired and henceforth incapable of adapting to a plethora of external stimuli, respectively experiences.

 

Our nervous systems
A neuronal network in blue with a black background.

Our body is basically being delegated by two distinct, overarching circuitries.

 

 

 

Our body possesses two distinct nervous systems, which pretty much guide the way we feel, think and behave.

 

 

I) Peripheral nervous system

The “PNS” allows us to perceive and process external stimuli, roughly speaking. It basically acts as a relay between the brain, the spinal cord and the rest of the body.

 

It can even further be divided into two parts

a) Somatic nervous system

It is in charge of carrying motor and sensor information to and from the central nervous system. Your skeletal muscles are being directed by your somatic nervous system – this means that any sort of voluntary movement, such as your raising an arm, is the direct result of your somatic nervous system’s partaking.

b) Autonomous nervous system

This part of your PNS can be regarded as the system, which takes care of your bodily household. It directs all sorts of involuntary movements, such as breathing, heart rate, blood flow and digestion.

 

It can be further broken down into two subcategories:

Sympathetic system

It regulates your fight-or-flight response. This primeval survival mechanism kicks in, whenever your body perceives some sort of threatening distress. It basically shuts down processes such as digestion, it causes your body to release adrenalin, raises your heartbeat and so forth.

The reason being that, if you were to encounter a wild animal (which constitutes a stressful event), surviving said unlucky encounter would be at the top of your innate bucket list. Digesting your daily intake in the face of death would be a most foolish course of action, as well as an unnecessary way of expending your energy reserves and thus be put to a halt immediately.

Parasympathetic system

This system describes your body’s normal way of conductance. Once a threat has been passed, this system kicks in again and reduces your heart rate, slows your breathing and reduces the blood flow to the muscles.

 

II) Central nervous system

This system consists of our spinal chord, as well as our brain. It is in charge of our emotions, thoughts, desires, and movements. It is also responsible for breathing, heart rate, hormonal release and a plethora of other bodily functions.

Our spinal chord serves as a quick means of reacting to specific external influences. This part of our body relays pieces of information from the brain the rest of our blood-driven vessel. Reflexive responses are also pieces of its repertoire – whenever sensory input related to pain makes its way through the highway of nerves, our spine immediately acts, without further delaying the necessary motoric movement needed to evade further hurtful inputs. So, whenever you touch a heated plate, you reflexively move back your arm without having to think about it.

By the way, experiments on animals have shown that input from the brain is not needed, when it comes to coordinating muscles necessary to walk. E.g. a cat, whose brain has been separated from the spinal chord – so that the brain is in no contact with its body – will spontaneously start walking, when placed on a treadmill. [4]

 

False localization

Sometimes, when a large peripheral nerve gets cut, a strange phenomenon has been observed – namely “cross-wiring” of certain nerves.

This occurs when axons reattach to axons of the wrong nerve. This “shuffling” basically results in a distorted sense of perception. Individuals who experience “false localization” may feel that their pinkie finger has been touched, even though it was their thumb.

Needless to say, these neuronal mishaps do not last too long, for our brain is able to change itself and henceforth unshuffle the signals from the wrongly crossed nerves.

 

Neurogenesis

Our neurons spring from a somewhat eternal fountain of youth, namely neuronal stem cells. These have been coined that way, for they are able to divide, as well as differentiate, in order to become neurons, respectively glia cells, which basically support other neurons in the brain. Stem cells, which are by the way not only present in the brain, but also in other parts of our body, principally pose as the framework for new cells. These parts of our body are able to produce exact replicas of themselves. This rejuvenating process, in regard to this specific subject matter, is commonly referred to as “neurogenesis”. [5]

Stem cells do not age per se, yet genetic mutations and the like take their toll on those biological springs. A state, where proliferation and division are no longer possible, is known as cellular senescence.

 

Periods of plasticity

Our super-processor houses billions of neurons, yet this number is, as you already know, highly dependent on a variety of factors. One such factor is actually age.

A light bulb shines forth and illuminates its surroundings.

It is best to make use of our innate plasticity as soon as possible.

Speaking in terms of language development, humans appear to maximize their growth during a specific timespan [6]. Said peak basically begins during infancy and ends somewhere between the age of eight years and puberty. Gaining proficiency in another language without an accent is way harder afterwards. In fact, languages which are learned subsequently are even processed in different parts of our brain, as compared to the native tongue.

Generally speaking, during said plasticity, way more neurons are generated than necessary. We need to differentiate between two general ways, respectively periods, of neuronal plasticity. These periods are commonly being referred to as “critical-period plasticity” and “adult plasticity”.

Critical-period plasticity, which is, as previously stated, apparent in infancy, allows the cortex of our offspring to simply change its structure by merely being exposed to new stimuli. This makes sense since the brain has yet to differentiate between stimuli, which are relevant in terms of survival and vice versa.

Adult plasticity refers to the period which occurs thereafter. Our brain is still highly plastic, yet it is more difficult to acquire new skills. [7]

4) Neural utility
Use it or lose it

It is important to understand that plasticity is a highly competitive process. Brain maps, which are out of use tend to give way to those that are regularly being tapped into. Linguistically speaking, as we age, we are naturally predisposed towards using our native language the most. As years go by said language dominates our linguistic map space. It becomes harder to acquire new skills as the old ones, which are repeated over and over again, solidify their mental prowess.

Think of it in this way: Our brain maps are tantamount to a snowy hill. The more we use our sled to speed down a specific trail, the harder it gets for us to leave said prefabricated track.

It is, therefore, best to practice new skills in the right manner from the get-go, so as to ensure that you do not stray from the correct route and slide down the path towards redundant territory. For unlearning is harder than learning – once a specific habit has been solidified, it becomes quite hard to get rid of. Mental maps, which have not been used in years actually do not go away completely. A slight stimulus related to a former habit will cause the respective neurons to fire again. Henceforth rejuvenating long gone trails.

 

Effective synchronicity

 

Ripples on a small patch of water can be seen.

A single ripple within our sea of thought can lead to an unprecedented cascade of internal processes.

As you already know by now, our neuronal structure can be altered by experiences. For such alteration to take place, our neuronal pathways need to fire together. A find, which appears to have first been proposed by Freud, but apparently conceptualized by Hebb. [8]

 

Experiments have shown that maps can merge together, if the respective motoric functions are intertwined, roughly speaking. Individuals, who suffer from syndactyly, respectively “webbed-finger syndrome”, have been born with fingers, which have been fused together. Brain-scans have revealed that said individuals possess a single, enlarged brain map for their fused fingers.

After surgical intervention, which resulted in a division between the erroneously fused extremities, follow-up scans have shown that the brain maps have thusly been split. This perfectly illustrates another principle of neuronal plasticity – neurons, which do not fire in accordance with each other, tend to wire apart.

 

 

Please note:

“Neurons that fire together, wire together.”

“Neurons that fire apart, wire apart.”

 

Cortical topography

Many of our daily activities consist of repeated sequences, which are performed in a consequent order. In order to illustrate this point, I would like you to imagine grabbing an object, the size of your palms, with your hands. We are prone to pick it up first with our index finger and with our thumb. Since both parts of our hand tend to almost simultaneously perform the previously explained task, its neurons tend to fire together. Such wiring can only take place, whenever neurons fire within thousandths to tenths of seconds. [9]

This means that the maps related to both the index finger and the thumb are formed closely together in our brain.

As the stated gripping process runs its course, we naturally use our middle finger next – this map is henceforth closer to the map of our index finger and further apart from the region allocated to the thumb.

It is important to note that signals, whose internal expression deviates in regard to time (e.g. signals from the pinkie and the thumb), result in more distant brain maps.

The modus operandi of most, if not all brain maps, consists of essentially clustering together events, which happen in concordance with each other. In a spatial manner, that is. [10]

 

Neuronal efficiency

As our brain maps grow in size, a process related to efficacy takes place in two stages. After training and somewhat enhancing our proficiency in a given field, the respective brain maps grow and therefore take up more space. Yet, as time goes by, individual neurons located within the map become more proficient. This leads to a decrease in neurons needed to perform a given task.

Human beings, who perform any sort of motoric tasks, such as playing the piano, are doing so first in a rather abrasive manner.  As this sort of acclimating process goes on, the processing speed of our neurons rises. Interestingly, the speed of our very thought processes is plastic.

Swiftness poses an important part in our survival. Speaking from an evolutionary standpoint, one has to take into account that events often happen quickly. If our innate super-processor were to be to slow on the uptake of stimuli, whose ambiguity is basically constantly a given, insofar as survival, respectively death goes, we could miss out on crucial pieces of information.

 

Solidifying plastic changes

Our brain processes an enormous influx of external stimuli during most of our waking hours. In order to ensure that stimuli, which appear to be of benefit to our survival, are being consolidated, specific neurotransmitters have to be released. Dopamine, which acts as a microscopic reinforcer, strengthens the particular reward. Whilst Acetylcholine aids our brain insofar as that it “tunes in” and sharpens mental “data”. [11]

5) Neuronal principles
Of nerve-growth factors …

Specific proteins, which are responsible for the growth of neurons, are released, whenever plastic changes occur. These molecular structures have been termed “NGF” or nerve-growth factor(s).

One such factor is most vital when it comes to reinforcing re-structuring mechanisms during critical period plasticity. Brain-derived neurotrophic factor, in short, “BDNF”[12], strengthens neuronal pathways in four distinct ways:

 

I) Whenever an activity ensues, which requires certain neurons to fire together, they release BDNF. This growth factor strengthens the existing neuronal connection in order to provide a certain reliability in the future.

II) This factor also promotes the release of a fatty coat around neurons. Myelin – the engulfing substance – speeds up the electrical transmission of those constructs.

III) The “modulatory control system of plasticity”- that is, a brain structure known as “nucleus basalis”, is being turned on by BDNF during the critical period. Said neurochemical system allows us to focus our attention on a given task and, when active, puts our brain into a highly plastic state.

BDNF basically ensures that this system stays active during the entire time of the critical period. Once it has been turned on, it not only acts as a precursor for focus but also helps us to remember things.

IV) After the task of strengthening key connections has been finished, it is also in charge of ending the awe-inspiring period of critical plasticity by turning off the nucleus basalis. Thus leading to a more stable way of neuronal activity.

 

I would like to emphasize the fact that this nucleus can only be turned on, whenever something novel, important or interesting happens, which poses as a particularly engaging stimulus. Another way of cranking up this mental gear is to pay close attention. Multitasking, which basically divides your focus should henceforth be avoided at all costs.

 

… and rats

Merzenich and his colleague, Mikel Kilgard, have found[13] an artificial way to reopen the window of critical period plasticity in rats. They inserted microelectrodes into the nucleus basalis and stimulated said region by means of electricity. Afterwards they exposed these little mammals to a 9Hz frequency in order to check, whether they could effortlessly develop a related brain map.

Under normal circumstances, the auditory neurons of an adult rat are only able to respond to tones at a maximum of 12 pulses per second. The abovementioned process related to the stimulation of the nucleus basalis allowed the neurons to respond to ever more rapid inputs.

The future implications of these findings are highly promising. A world, where we could simply stimulate the nucleus and greatly enhance our mental prowess in terms of informational uptake would allow us to almost effortlessly gain new knowledge.

 

Intensive Learning

One of the biggest reasons for the decline of our internal systems, which regulate, modulate and control plasticity, is our neglect of intensive learning.

As we age, our processing speed declines[14], which in turn causes a reduction in regard to the accuracy, strength, and sharpness of our perception. This causes us to struggle when it comes to registering new events. This unclear registration means that we won’t be able to remember the respective influx well.

When our mental system gets noisier, we have trouble forming strong memories, since the electrical activity in the background of our minds diverts our neural resources.

 

Signal-noise problems
A vinyl record is being used.

Simply repeating the same sequence over and over again, like a broken record, diminishes our neuronal capacities.

There are two reasons, why our system gets noisier. One is the result of a gradual decline in cognitive abilities brought about by the unforgiving ravages of time. The second being a neglection of our nucleus basalis. This compartment of our brain works with acetylcholine. A neurochemical substance, which aids our memories insofar as that they get sharper and more tuned-in.

The production of acetylcholine in Individuals, who suffer from a mild form of cognitive impairment, is not even measurable. This is an immediate result of a lack of proper mental exercise.

As our time goes by, we fool ourselves into believing that we are learning as we were before. You see, as we get more proficient in our given profession, we simply tend to repeat already ingrained courses of action. The same goes for other learned skills, such as reading the newspaper or speaking our own language.

By the time we are 70, we may have been plastically stagnant for about 50 years. This also explains, why learning a new language during old age is one of the best ways to remain mentally vigilant. All activities, which require you to exert an enormous amount of focus will keep your mental super-processor sharp.

6) Conclusion/Related reading

Sharpening our mental saw in a continuous manner by means of steadily engaging in new activities, whilst remaining highly focused is of paramount importance. As you know by now, our brain shapes our reality. The higher our innate mental prowess, the better our lives get. So what are you waiting for? Pick up that book that you’ve wanted to read for way too long; start learning a new language or begin learning an instrument – you have nothing to lose, but everything to gain!

If you wish to heighten your knowledge in regard to our brain’s plastic capabilities, I usher you to get the following book:

Do you enjoy my articles? If you wish to be immediately notified, whenever a new one has been published, please consider subscribing.

7) References
References
  1. Herculano-Houzel, S. (2009). The Human Brain in Numbers: A Linearly Scaled-up Primate Brain. Frontiers in Human Neuroscience3, 31. http://doi.org/10.3389/neuro.09.031.2009
  2.  Jordan Grafman, Conceptualizing functional neuroplasticity, Journal of Communication Disorders, Volume 33, Issue 4, 2000, Pages 345-356, ISSN 0021-9924, https://doi.org/10.1016/S0021-9924(00)00030-7.
  3. Fares, R. P., Belmeguenai, A., Sanchez, P. E., Kouchi, H. Y., Bodennec, J., Morales, A., … Bezin, L. (2013). Standardized Environmental Enrichment Supports Enhanced Brain Plasticity in Healthy Rats and Prevents Cognitive Impairment in Epileptic Rats. PLoS ONE8(1), e53888. http://doi.org/10.1371/journal.pone.0053888
  4. Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. Spinal Cord Circuitry and Locomotion. Available from: https://www.ncbi.nlm.nih.gov/books/NBK11015/
  5. Sierra, A., Encinas, J. M., & Maletic-Savatic, M. (2011). Adult Human Neurogenesis: From Microscopy to Magnetic Resonance Imaging. Frontiers in Neuroscience5, 47. http://doi.org/10.3389/fnins.2011.00047
  6. Rosselli, M., Ardila, A., Matute, E., & Vélez-Uribe, I. (2014). Language Development across the Life Span: A Neuropsychological/Neuroimaging Perspective. Neuroscience Journal2014, 585237. http://doi.org/10.1155/2014/585237
  7. Lövdén M, Bäckman L, Lindenberger U, Schaefer S, Schmiedek F.,  A theoretical framework for the study of adult cognitive plasticity., Psychol Bull. 2010 Jul;136(4):659-76. doi: 10.1037/a0020080.
  8. Keysers, C., & Gazzola, V. (2014). Hebbian learning and predictive mirror neurons for actions, sensations and emotions. Philosophical Transactions of the Royal Society B: Biological Sciences369(1644), 20130175. http://doi.org/10.1098/rstb.2013.0175
  9. Julesz, B., & Kovács, I. (1995). Maturational windows and adult cortical plasticity. Reading, Mass.: Addison-Wesley.
  10. Patel, G. H., Michael, D. K., & Snyder, L. H. (2014). Topographic organization in the brain: Searching for general principles. Trends in Cognitive Sciences18(7), 351–363. http://doi.org/10.1016/j.tics.2014.03.008
  11. Hasselmo, M. E. (2006). The Role of Acetylcholine in Learning and Memory. Current Opinion in Neurobiology16(6), 710–715. http://doi.org/10.1016/j.conb.2006.09.002
  12. Bathina, S., & Das, U. N. (2015). Brain-derived neurotrophic factor and its clinical implications. Archives of Medical Science : AMS11(6), 1164–1178. http://doi.org/10.5114/aoms.2015.56342
  13. Kilgard MP, Merzenich MM., Science. 1998 Mar 13;279(5357):1714-8., Cortical map reorganization enabled by nucleus basalis activity.
  14. Eckert, M. A., Keren, N. I., Roberts, D. R., Calhoun, V. D., & Harris, K. C. (2010). Age-Related Changes in Processing Speed: Unique Contributions of Cerebellar and Prefrontal Cortex. Frontiers in Human Neuroscience4, 10. http://doi.org/10.3389/neuro.09.010.2010

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