How does ADHD affect neuroplasticity
4.2. Excursus: neuroplasticity
Overview back next
Neuroplasticity = active adaptability of the brain.
This ability plays an important role in medicine and I will go into this here: motor learning, chronic pain syndromes, phantom pain, ADHD, ADD, stroke, traumatic brain injury, dyslexia, aging processes and depression.
Overview of the most important scientific results:
- The brain isn't hardwired.
- The expansion of the brain areas of body regions increases with frequent use.
- Learning processes activate stem cells in the brain and improve nerve connections.
- Nerve cells cannot multiply simply by dividing.
- Old people also form new nerve cells in the brain through stem cell activation.
- New nerve cells can develop from supporting nerve cells.
- The mind can change the body, e.g. through training or meditation.
- Experiences activate one's own genes individually.
- Parents' behavior changes the chemistry of their children's and grandchildren's genes.
- Parents' behavior changes their children's brains.
- Our thinking and our actions can significantly change our future thinking and actions, mentally and physically.
- We decide who we want to be tomorrow.
The brain isn't hardwired.
Until a few years ago it was believed that the brain had a fixed number of nerve cells with invariable connections. Today we know that the brain can change in a targeted manner at any time in life. This happens through neuroplasticity, i.e. through adaptation of the nerve cells. The brain makes more tissue available for functions that are carried out frequently. The brain enlarges its area, e.g. for finger motor skills in a violinist. In the same way, a certain way of thinking can also lead to mental change. We can always recreate ourselves with new patterns of movement and new thinking structures.
Below is a chronological overview of the discoveries of neuroplasticity:
The expansion of the motor cortex (cerebral cortex) depends on the frequency of use and is constantly changing.
The motor cortex is the area of the brain that is responsible for movement. In an animal experiment around 1917, Sherrington demonstrated that the motor cortex is very individual, depending on how intensively the movements take place, the larger the corresponding brain area.
Learning processes occur because the same information is perceived repeatedly (Hebb 1949). Neurophysiologically it takes place like this: If two neurons fire at the same time, then over time they fire more strongly and become more easily excitable. The brain builds "roads" in a network and "highways" when used very frequently.
"Repetition is the mother of wisdom" (repetitio est mater studiorum), this creates "highways" in the brain. In this way everyone learns their own typical motor skills. The toddler his gait, the school child his writing. The athlete his specific technique ...
But: Creativity does not run on "highways", but on the possibility of other paths. Maybe that's why creative children get bored at school when a lot is repeated. Boredom does not build "highways" and does not encourage detours, these are then underachievers who get bad grades. Or these children react with an increased / compensatory urge to move, which we call hyperactivity (ADHD, ADS).
In this way, chronic pain also arises. With constant pain, a "highway" forms in the nervous system, which is permanently active, even if the triggering cause of the pain is no longer there.
Information is not only passed on to synapses.
(D. Dietrich, Clinic for Neurosurgery, University of Bonn, 2007, www1.uni-bonn.de)
The transmission of information from neuron to neuron does not only take place at the synapses - these are the contact points between the nerve cell extensions. Apparently, the neurons also release messenger substances along the entire length of their extensions and thus excite neighboring cells. The results don't just shatter basic ideas about how our brains work.
A severed sensory nerve loses its responsible brain area.
Michael Merzenich can be described as the father of the discoveries of neuroplasticity. In 1983 he cut a nerve on the hand of monkeys, which leads to the brain for the feeling of 3 fingers. The responsible area in the cerebral cortex was then taken over by nerves from the neighboring region.
That's how he went about it. Monkeys were stimulated with a brush in many different places on their hands under anesthesia. With the skull carefully opened, the scientists inserted a thin probe into the relevant brain region. In this way, the irritated skin region generated small currents in the relevant brain region. This is how a map of the brain can be drawn (drawing 1).
The measurements were repeated after severing a nerve (drawing 2) and after amputating a finger (drawing 3).
From: Reorganization of Cortical Representations of the Hand Following Alterations of Skin Inputs by Nerve Injury, Skin Island Transfers, and Experience.
M. Merzenich, W. Jenkins. Journal of Hand Therapy 1993
Drawing 1. Normal conditions:
3b region of the sensory cortex (= cerebral cortex for sensitive inputs)
A = cortex (= cerebral cortex)
B = section from 3b region for fingers D1 to D5. The dark fields correspond to the back of the hand, the light fields to the palm (palmar side)
Drawing 2. Experiment with cutting a sensitive nerve:
A Normal distribution of the median nerve, radial nerve and ulnar nerve on the hand.
Above: Left: palm (glabrous) and right extensor side (dorsum).
Below: normal representation in the cerebral cortex (sensitive cortex). The trackside representative offices are shown in gray again.
B Above: After severing the median nerve, its region becomes numb (anesthetic skin).
Below: The representation of the median nerve disappears in the cerebral cortex, only a smaller area on the extensor side of the first 3 fingers of the radial nerve remains detectable in the cortex. The brain region for the 4th and 5th fingers from the ulnar nerve enlarges.
The same happens when a finger is amputated:
A Normal representation of the 3rd finger (gray) in the cerebral cortex.
B After amputation of the third finger, the area of the brain is taken over by the neighboring fingers.
C The region of the hand marked in gray is represented in the remaining area D3 of the cerebral cortex.
Repeated stimulation of a sensitive nerve enlarges its brain area.
A nerve that is responsible for feeling conduction (sensitive nerve) gets an increasingly larger brain area when it is repeatedly stimulated. This corresponds to a learning process / training.
Attempt by Jenkins:
Monkeys keep holding a rotating disc between two fingers. If the monkey holds too tightly, the disc will stand still. If it is held too loosely, the hand will be thrown away by centrifugal force. If he exerts moderate pressure, the fingers stay on the disc without stopping and without being thrown away. If he manages this, he gets a treat. Electrode measurements in the brains showed that after several weeks the corresponding brain area quadrupled.
Repeated stimulation of a motor nerve enlarges its brain area.
Try from Nudo:
4 squirrel monkeys practiced hundreds of times with one finger to fish delicacies from a bowl with a constriction for several days. The motor cortex doubled for this finger without negatively affecting the neighboring regions.
Brain areas are not defined locally.
Result: Sensitive signals from the arm can be directed to the cheek and acoustic signals can be directed into the visual cortex. The localization of the brain areas in the cortex does not seem to play an essential role (attempts by Taub and Sur).
Was known: Nerve cells cannot multiply simply by dividing like skin cells, for example.
Learning processes activate stem cellsthat grow into the cortex as new neurons.
Famous attempt by Nottebohm in 1983: Canaries learn a new melody every spring. The responsible brain area is then 99% larger than in winter. He injected them with radioactively labeled thymidine (= component of cell nuclei) every day. A month later he found thousands upon thousands of new brain cells. They were activated from stem cells in the ventricular region and grew as new brain cells in the cerebral cortex.
Learning processes improve the nerve connections.
Rats that grow up in a stimulated environment have larger synapses (= connecting gap between nerves), more dendrites (= connecting arms between nerves), larger nerve cells, larger cell nuclei, higher transmitter production (= chemical compounds of the synapses) and more active glial cells (= supporting cells) than rats from a less stimulating environment. This structural change leads to different behavior, making the stimulating environment "more intelligent" (Greenough, Rosenzweig).
Fred Gage is a brain researcher with a special family tradition. He is a descendant of Phineas Gage, a famous railroad worker who was shot in the head with an iron bar in an explosion. He lived for many years with a few changes in behavior.
Old people also form new nerve cells in the brain through stem cell activation.
Gage heard from cancer patients in Sweden who had been injected with radioactive labeled DNA to find metastases. In these patients (50-80 years old) Gage examined the brain histologically after their death. 500 to 1000 new Neurons / day had formed from neuronal stem cells in the hippocampus and grew towards the cerebral cortex.
Such new brain cell production was later found to be triggered by exercise, calorie restriction, a stimulating environment, brain trauma, estrogen, marijuana, growth factors, serotonin, and electroshock therapy. A slowdown in the formation of new brain cells was found with increasing age, serotonin and sleep deficiency, stress, alcohol, opiates and metamphetamines.
The performance of the brain can be maintained and improved through training programs. E.g. by learning a new poem every day, sodoku or through a scientifically developed program http://support.positscience.com.
After brain injuries: New nerve cells develop from neural supporting cells (glia).
Most of the cells in the human brain are not nerve cells, but supporting cells (glial cells). They serve as a scaffold for nerve cells and play an important role in the wound response that occurs when the brain is injured. How these 'reactive glial cells' in the brains of mice and humans develop and what cells they develop into, however, were previously unknown. Glial cells in the mouse brain resume cell division after injury. They then become stem cells from which nerve cells can be formed again. In 2008, the groundbreaking proof was thus achieved that adult neural stem cells are present in an injured region of the brain, which could then serve as a source for new nerve cells.
(according to Prof. Magdalena Goetz, Helmholz Center Munich. www.helmotz-muenchen.de)
Gage showed in mice that when they voluntarily walk they formed more new neurons and became smarter in the test. However, neurogenesis and learning skills were only increased when running was voluntary. Physical activity alone was not enough.
Conclusion: Learning only works voluntarily. An active lifestyle prevents aging.
Infants have twice as many neurons as adults.
Around 100 billion neurons with an average of 2500 connections with other neurons. By the time they are 3 years they have an average of 15,000 links, a maximum of 100,000. After the age of 4, we have lost half of our neurons.
The brain has set development times for certain skills.
Infants lose the ability to distinguish phonemes. Classic experiment: 7-month-old Japanese babies could distinguish an English R from an English l, while 10-month-old babies could no longer tell. The auditory cortex loses its ability to store new phonemes. The same applies to visual skills, e.g. being able to distinguish Asian faces.
Nerve cells are not localized.
In people without a sense of hearing, the performance of visual neurons is significantly increased. The auditory area of the brain can at least be used for peripheral vision and movement perception. The sense of hearing is therefore not anatomically defined.
This extreme neuroplasticity decreases with age. Anyone who becomes blind after the age of 15 can no longer restructure their visual cortex so radically that, for example, the sense of touch increases significantly. However, some degree of neuroplasticity is retained here at any age as well. At least 15% of neurons can be changed by experience at any age.
Attention improves e.g. dyslexia (Paula Talla).
Most dyslexics cannot differentiate between sounds because people speak too quickly. In the FastForWord program, tapes with artificially stretched speech are played to the children and then increasingly faster. After 20-40 hours of training, these children were able to distinguish fast sounds better than non-dyslexics. After 1 month, her speech development was 2 years further. In half a million children across the United States, 90% of dyslexics were able to improve reading skills after 6-8 weeks, giving them a language development of 1.5 to 2 years.
Neurons damaged by a stroke are capable of regeneration.
Edward Taub's CIM therapy (constraint-induced therapy) from 2000 and 2006 for stroke patients:
The functional opposite arm is worn in a sling for 90% of the waking time for 14 days. 10 days of 6 hours of intensive training with the paralyzed arm. If the patient cannot actively do this to the full, then active support from an auxiliary person.
Study: 41 stroke patients on average 4 years after stroke. Half of them were treated according to CIM and their motor skills were significantly better after just 2 weeks, which was retained 2 years later. The "learned non-use" is thus overcome. The brain is reorganized through previously unused areas of the brain.
With transcranial magnetic stimulation, Taub showed that the motor cortex of the paralyzed hand became twice as large and the neighboring regions were also activated. The earlier and more intensive the therapy, the better the results.
Since the therapy is very time-consuming, Taub developed an automated version of AutoCITE. A 2004 study showed that the effects are just as good with this.
The motor cortex is specifically enlarged in musicians.
String instrument players have a very large motor area for the left hand, especially if they started playing before the age of 12.
Behavioral therapy and medication work about equally well for depression.
Depression study Gavin Andrews 1996
250 patients with 4 treatments:
- Interpersonal therapy:
External events that led to depression, such as the situation with the children leaving the house, are treated as the cause of the distress.
- Cognitive behavior therapy:
Learn to deal with your thoughts differently and not ponder endlessly about small setbacks. The reality of interpersonal relationships was reasonably checked, which showed them unrealistic pessimistic attitudes.
It is primarily a mindfulness training (S 261) in which the patient concentrates on consciously feeling individual body regions, e.g. knees, feet ... and finally breathing. If you wander with your thoughts, you simply return to the topic. The breath acts as a magnet back to the attention of the moment.
Thoughts and feelings are observed impartially, only looked at, not evaluated and let go, like a butterfly fluttering through the field of vision.
Most importantly, keep telling yourself that your thoughts are not truthfully reflecting reality.
- Imipramine (antidepressant drug)
Imipramine worked best, placebo worst, the other two therapies were in between, and just as good as imipramine for milder depression. By marketing, antidepressants are believed to be more effective.
Placebo and antidepressants work equally well.
PET examination (positron emission tomography) by Helen MAYBERG 2002 showed that antidepressants work just as well as placebo. Trial with 27 depressed patients. One half was treated with Praxil, the other half with cognitive behavioral therapy.PET showed that behavior therapy dampened overactivity in the frontal lobes (mind, logic, analysis of higher thoughts, including cloudy thoughts)
- Praxil increased the activity here.
- Behavior therapy increased activity in the hippocampus of the limbic system (center of feelings),
- Praxil reduced the activity here.
- Behavioral therapy affected other areas of the brain that Praxil did not reach.
- Behavioral therapy works top-down, Praxil bottom-up.
Attention-based behavior therapy breaks the depression circuit.
The mind can change the body.
A group learns a 5-finger exercise on the piano for 5 days for 2 hours each.
A comparison group only learned the exercise by thinking about it but not doing it. The activity of brain cells can be localized by means of transcranial magnetic stimulation. The motor cortex for the hands increased equally in both groups.
(Pascual-Leone 90s, Harvard)
Attention causes the mind to affect the brain organically. Attention is needed for neuroplasticity.
Experiment Michael Merzenich:
2 groups of monkeys
1st group: fingers stimulated every day for 6 weeks with a grooved turntable. They heard certain tones through headphones. Conditioned with attention: if the turntable was changed, they got fruit juice. So they paid attention to fingers, not sounds.
2. Group got a reward if the tones changed, but fingers were also on the turntable.
The physical stimuli of finger stimulation and hearing the sounds were the same in both groups. Difference only by paying attention.
6 weeks later: Motor cortex was only found in those conditioned on finger touch, not in the others.
The attention thus decided on the organic enlargement of the motor cortex.
Merzenich: "We decide in a very real sense who we will be in the next moment, and these decisions leave a physical imprint on us."
Experience is passed on individually by activating genes (epigenetics).
The water flea forms a kind of helmet and spiked tail when it grows up in a hostile environment (fish). If you take a water flea into an aquarium without fish, the armament does not grow. If you put a clone in an aquarium with fish, the weapons grow. If you reset it, the weapons shrink.
If a water flea that has seen fish lays eggs, the next generation will grow bigger guns, even though they never saw an enemy (Michael Meany).
A common phenomenon in nature, what is called so. Epigenetics has become a huge area of research.
“The difference between genetics and epigenetics can probably be compared to the difference between writing and reading a book. After a book is written, the text (the genes or the information stored in the DNA) is the same in all copies distributed to the interested audience. However, every single reader of the book will interpret the story in slightly different ways, with feelings and expectations developing differently as the chapters progress. In a very similar way, epigenetics enables different interpretations of a fixed template (the book or the genetic code), which leads to different readings depending on the variable conditions under which the template is viewed. "
(Thomas Jenuwein http://epigenome.eu/de)
The 19,042 chromosomes in humans consist of 50% genes (contain 3.2 billion DNA building blocks) and 50% proteins (epigenes), which can switch genes on or off by adding methyl groups. Obviously, this can be done for a specific purpose.
According to this, Darwin's theory of evolution, which assumes spontaneous mutations and natural selection, would be wrong. The current findings in epigenetics speak in favor of Lamarck's forgotten theory of evolution. He claims, for example, that giraffes have always stretched for the seductive foliage of the treetops, which has made giraffes' necks a little longer from generation to generation.
The living conditions influence the hormonal balance through the quantity of the formation of receptors.
It had been found that rats change their behavior when exposed to different situations in the first 21 days of life.
2 groups of rats. A were separated from their mothers 15 minutes a day, B not. In adulthood, A rats had better stress control, as measured by the cortisone level after an electrical surge.
They only needed a small amount of cortisone to develop stress, so they reacted more sensitively. The cause was the increased formation of receptors for cortisone in the hippocampus due to increased activation of the corresponding gene.
Same observation in boys by caring and non-caring mothers (licking and cleaning).
"Genes can be silent or active. The activity of a gene is determined by its environment, i.e. the chemical environment in which the genes operate, and this is modified by the level of parental care."
Parents' behavior changes the chemistry of their children's genes.
Character traits are not fixed unchangeably in genes. Character traits are not fixed unchangeably in genes. The rules of epigenetics then apply not only to physical expression, but also to psychological manifestation.
Caring female rats were also caring for their offspring, and neglected rat mothers neglected their offspring.
Stress-ridden mothers neglect their children, who become nervous and anxious and are therefore well adapted to the harsh living conditions.
By neglecting them, mothers prepare their offspring for poor living conditions with better chances of survival (Meany).
So a natural selection in evolution.
The same could be proven in 2 studies for people who grew up in poverty and a criminal environment. In contrast to children who are better off, poor children have higher levels of stress hormones, which have an undesirable impact on their brain and lead to lower intellectual ability and lower emotional control. Children who are neglected or abused are more responsive to stress hormones. Lots of human studies show that neglecting mothers produce anxious children, for example. Organically different brain activities demonstrated in the comparison groups.
This means: Parents have to bring up children with care so that they can be caring for their children again. However, the neglected are more viable and are more likely to prevail in evolutionary terms. They fail because their intellectual abilities are lower.
Parents' behavior changes children's brains.
Investigations by the University of Magdeburg and Leipzig (www.uni-magdeburg.de)
- In the first days of life, Degujung were "shaped" by the call of their mother, i.e. they form an association between the call and a positive emotional situation (being sucked, warmth, emotional affection from the mother).
- The maternal call led to increased activity (measured as the uptake of 14C-fluorodeoxyglucose) in the precentral medial and anterior cingulate cortex (limbic system) in the young animals.
- Even after a very short separation from the parents, there are reductions in synapses in the limbic system.
Conclusions from the animal experiment results:
Especially the very early emotional experiences, ie shortly after birth and in the first weeks of life (rodents) or years (primates including humans) have a lasting ("formative") effect on the development of the brain (limbic system, which is responsible for feelings responsible) and behavior.
Intact parent-child contact is essential for the development of brain function and behavior.
If we are to educate our children in compassion and altruism, the first step is to give them an emotional foundation. More than a dozen studies have shown that attachment behavior is crucial. A mother who avoids attachment creates children who avoid attachment (SHAVER).
Meditation changes the way the brain functions organically.
After 30 years of meditation for compassion, the monk "Happy Gift" was 99.7% more active in the left front brain area than other people.
Larger activities in the left front brain area are associated with positive emotions such as happiness, right front dissatisfaction and unhappiness.
In many monks' brain MRI studies, it has been shown that these activities not only exist during meditation, but become a permanent property.
The mind is trainable.
Everyone knows that the body can be trained through exercise. The same is true of the mind. Buddhism means that you can also train feelings. Even today, the Dalai Lama meditates daily to improve his compassion.
A purely mental process can have measurable effects on the brain.
Feelings can be influenced by meditation.
Davidson MRI Study
Meditation on compassion creates activity in the "right insular cortex" and "caudate nucleus". It is known from other studies that these regions are linked to empathy and maternal love. Strongest with masters, less with other monks with meditation experience and least with beginners.
In the case of the monks, other areas that are generally active in emotions and happiness were also active.
Davidson recommends 1 hour daily meditation on compassion. "Neuroplasticity will counterbalance the deterministic view (that genes determine behavior).
The message I get from my own work is that I have a choice in how to respond. Who I am depends on the choice I make. I am responsible for what I am. "
New thoughts New brain, Goldmann Arkana. From the Mind and Life Conference 2004, by Sharon Begley.
Reorganization of Cortical Representations of the Hand Following Alterations of Skin Inputs Induced by Nerve Injury, Skin Island Transfers, and Experience. Journal of Hand Therapy, April-June 1993, M. Merzenich, W. Jenkins.
The world in a single atom, Theseus Verlag 2005, Dalai Lama.
Human Physiology, Springer Verlag 1995, R. Schmidt, G. Thews.
The day my leg went away, Rowohlt Verlag 1991, O. Sacks.
Epigenetics, Dumont Verlag 2009, B. Kegel.
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