by Zeev Nitsan
With regard to spotting the source of sounds, the “stereophonic gap” is a time gap of several thousandths of a second in the echoing of sound waves between the two ears.
People with one-ear hearing might rely on changes in the intensity of sound waves when they are echoed from the surface and from various textures in the environment to help them find the direction of the source of sound.
Loss of the depth dimension might take place at the time of perceiving a visual input—which will cause the loss of stereoscopic ability—and with regard to perceiving an auditory input—the loss of stereophonic ability. The depth dimension enriches the ability of experiencing world phenomena, and, on the practical aspect, it serves as an efficient tool for assessing the distance from the viewed, or heard, phenomenon. Some claim that the omission of the depth dimension from the auditory or visual input makes the perception of the experience duller also, in the sense of the emotional echo it triggers.
The Anarchic Hand Phenomenon
The alien or anarchic hand phenomenon, which appears in the degenerative brain disease called “corticobasal degeneration (CBD),” is reflected in a condition in which one of the hands acts in an independent manner, without the patient’s voluntary sense of control. A CBD patient described that while one of his hands was buttoning up his shirt, the other hand was involuntarily unbuttoning them. A process of “alienation” takes place. The hand becomes a stranger to its owner with respect to his sense of control over it.
Aspects of Brain Rehabilitation Following an Injury
Aspects of Rehabilitation of Motor Function
When the brain suffers from an injury, it tries to improvise a response in an attempt to compensate for the damage.
The brain’s compensation ability depends on the severity and duration of the damage and also on the networking patterns that characterize the specific brain.
When the traffic of signals in the neural pathway is disrupted, the brain tries to compensate for that by exposing bypass routes that are intended to preserve the neural network in a functional mode and to enable the signals to be transferred from the original location to their destination. The brain attempts to do so even if it is done not through the main road, and even through pathways that resemble winding, mountainous courses. As these pathways are used time and time again, they become wider and more user-friendly.
In the hope of rehabilitating their brain, people with nervous system injuries often walk down arduous paths of treatment.
A key question with regard to rehabilitation of patients who suffer from neurological damage focuses on how to induce inactivation of the prior action pattern, which is no longer applicable after the injury, and, at the same time, promote new learning in the shortest way, in an attempt to avoid the arduous process of prolonged practice that deters many of the patients.
Among the principles of optimization of rehabilitating function, as shown in various studies, there is the focused, short practice, which shows more concrete improvement compared to practice that spreads over a longer period of time with lower frequency of practice. The patient should be faced with challenges with a rising level of difficulty. The practice should focus on skills that are similar to those required for daily functioning.
In brain injuries that involve disruption of the natural skill of walking, sometimes it is worthwhile to learn how to walk from the beginning while being provided tools to cope with the deficiencies that caused the disruption. Such learning creates a new networking of the brain map, which encodes walking, instead of the old map, which is worn and disrupted, and skills that compensate for the brain damage are imbedded in the new map.
It is somewhat similar to reacquiring “gravitation feet” among astronauts who return from missions in space that involve conditions of almost zero gravity. The astronauts need a few days of practicing walking—like infants who take their first steps—until their “earthy feet” come back to them.
In a case of a broken limb that does not function, as in a case of a prolonged period of wearing a cast on a joint of a limb that prevents normal movement, the limb loses its “representation areas” in the representation maps of the body in the brain for the sake of functional areas in the body, which deprives it of its territory. If the limb’s function is fully or partially retained, however, it is forced to reconquer the territory of its brain representation. The rehabilitation of the limb itself is not sufficient. In order for it to function appropriately, the rehabilitation of its neural representation in the brain is also needed—in the absence of which, the function of the limb will remain faulty, even after the limb has fully recuperated.
The brain map representing the injured limb unweaves and dissolves due to limited use or lack of use. This process is called “acquired lack of use.” As if in a vicious circle, the tendency of acquired lack of use is reinforced, and the disability becomes more and more fixed. Studies show that, among people who suffer extreme weakness of the arm following a stroke, the motor representation map of the arm shrinks up to half of the representation territory it had prior to the damage. Reversing this trend by forced activation of the limb and reviving the neural network—i.e., the brain map that encodes the function of the limb—sugarcoats the pill and often greatly improves function of the damaged limb. In the case of limb weakness due to brain damage, it was found that intentionally restricting the movement of the opposite, healthy limb forces the brain to use the damaged limb, and its function is improved in the long term. A similar principle is used in treating a “lazy eye” (an eye that does not function well at the level of the cortex that processes the visual information coming from it): an eye patch that is worn over the healthy eye forces the brain to use the lazy eye, and the performance of the brain areas that process the information deriving from it improves as time goes by. The treatment is successful, especially during the time window of early childhood. The brain creates new networks of function maps based on the new artificial constraints. It seems that many rehabilitation programs for improving brain functions can benefit from these findings.
Tourette’s syndrome is characterized by meaningless movements (ticks), which the person who suffers from the syndrome feels an irrepressible urge to perform. One possible treatment of the syndrome is to try to recruit these forced spouts of movement for the sake of focused, target-oriented actions that result in purposeful behavior.
Life as a song: People who suffer from brain injuries, particularly at the frontal lobes, which cause difficulty in performing sequences of daily activities, might find it helpful to use functional directions for performing a sequence of actions transcribed as a rhymed song with a familiar melody.
Aspects of Rehabilitating Speech
Aphasia is damage to the skills of producing or understanding speech.
When we produce speech, our brain exchanges a sequence of symbols, in the figures of words that conceptualize thinking, for a sequence of movements in the muscles of the pharynx, the tongue, the palate, and the lips. It seems that the brain area that orchestrates these movements into a single melodic sequence is the premotor cortex at the left frontal lobe. An injury at this area is commonly reflected in difficulty with producing syllables (phonemes)—the basic units of speech.
Semantic aphasia is the inability to process representations, symbolization objects, and abstract concepts, and it mostly derives from injury at a particular area in the left, temporal lobe, which is in charge of granting meaning to the contents of speech. In accordance with the severity of injury, people who suffer from such injury have difficulties in understanding the contents of speech when other people speak; on the other hand, the content of the sentences they produce is usually incomprehensible (gibberish), or embedded with meaningful islands surrounded by a sea of meaningless wording.
According to common estimation, about 40 percent of people who have had a stroke in the left hemisphere suffer from aphasia. In those cases, it was also found that an intense practice program improves the condition more signif
icantly compared to prolonged practice programs with long intervals between one training period to the other.
It was found that the people who suffer from aphasia, who are unable to talk, are sometimes able to sing. The fact that the stream of words has not dried up completely might serve as an encouragement for them. It seems that a familiar composed transcription, in which threads of emotion are weaved and whose content is “ready-made” and does not require “syntactic engineering,” often enables them to overcome the wall of aphasia that blocks purposeful speech, and it is based on self-creation of contents and syntax.
A concrete example of rapid acquisition of an acquired skill is acquiring a new language while staying in a foreign country. The constraint of communicating in the local language; the intense, frequent exposure; the daily implementation—all of these accelerate the pace of language acquisition and deepen its traces in our brain. Similarly, intense and frequent exposure to practicing of language skills usually accelerates speech rehabilitation among those who suffer from aphasia.
Aspects of Coping with Degenerative Brain Diseases
Nowadays, treatment of degenerative brain diseases might seem like a sequence of rearguard battles intended to slow down degeneration. Sometimes the shreds of functioning that survived in the shattered brain cannot be patched up—brain plasticity also has unfortunate limitations that cannot be overcome.
Brain diseases, especially those that affect the frontal lobes, are able to reshape personality and calibrate beliefs, habits, and typical behaviors in a new pattern.
Dementia deprives the brain of its most magnificent assets. The consequences of dementia are destructive. A brain of a wise person who suffers from dementia resembles an architectural masterpiece that turned into ruins following an earthquake.
Patients who suffer from dementia, which envelops their consciousness in loneliness, are like a wanderer in the wilderness of the cold tundra; they are accompanied only by a gloomy silence and sometimes warm themselves up in the light of music, which is capable of wakening dormant emotions.
Physical Exercise and the Brain—the Brain in Sports Shoes
Physical exercise intensifies the creation of new neurons in the brain.
An experiment that was conducted on mice showed that urging them to perform aerobic physical exercise doubled the pace of the production of new neurons in the brain area called the dentate gyrus, which is located in the hippocampus. Other studies also found that aerobic physical exercise is a habit that has maximal positive effect on the brain.
Brain researcher Art Kramer and his associates found that among people at the age of sixty and above who regularly performed aerobic exercise for a period of six months, there was an increase in the volume of the gray matter in the frontal lobes, which are considered the most vulnerable to aging. In addition, they found thickening of the volume of the white matter in the corpus callosum, an area in which there are numerous axons that constitute a “latitude road” that mediates the streaming of information between the two hemispheres. At the practical level, the active group demonstrated improved performance with respect to focusing attention and the ability to ignore distracting information (functions that are ascribed to the frontal lobes).[38]
Physical exercise also triggers the production of brain-derived neurotrophic factor (BDNF), which also has an important role with respect to the structural and functional flexibility of the brain.
As we further expand our education and become more active physically and more socially involved, we improve our coping capabilities, and our potential compensation repertoire, related to coping with the process of dementia in the unfortunate case it affects us in the future.
Aspects of Rehabilitation of Emotional Regulation
Long periods of stress or deep depression might cause a reduction in the size of the hippocampus. On the other hand, it was found that antidepressant drugs that increase the level of the neurotransmitter serotonin at the neural junctions brings about an increase in the amount of stem cells that turn into neurons in the hippocampus.
Usually it takes three weeks or more until the effect of such an antidepressant is noticeable. It is also the duration of the period required for newly created neurons to network themselves in the hippocampus and create new neural pathways. Thus, some of the antidepressant drugs might have a neurotropic effect—one that encourages the thriving of neurons and their links. It might be wise to prescribe them as part of the routine therapeutic process in cases of other degenerative brain diseases like Parkinson’s and Alzheimer’s.
Doctors of the soul have noticed that therapy that includes talks improves patients’ mood, and the ability to perform cognitive tasks, among those who suffer from depression. It might be that a therapeutic talk can change the biochemistry in the brain to such an extent that creation of new neurons in the hippocampus is encouraged and networking among them is intensified. According to this supposition, we might be able to claim that words are formed into new links between neurons.
In the case of adults who suffer from depression and also experienced a traumatic event during childhood, it was found that the volume of the hippocampus is about 20 percent smaller compared to adults who suffer from depression but did not experience significant trauma during childhood. When stress does not last long, there is a component of reversibility, and the original size of the hippocampus is restored. It seems that beyond a certain period of time, however, the damage is for good.
How the Brain Copes with Injury
Injuries in the structure of the brain, such as in areas that remain scarred after strokes, usually do not have a linear connection to functional loss. The correlation between them is usually related to a certain threshold. In other words, once the structural injuries cross a certain threshold, which derives from their accumulated effect, it results in a significant functional impairment that was not noticed at the subthreshold level.
Shades of gray: The effects of brain injury can be noticed on a spectrum. Damage to the gray matter and the white matter in the brain is often manifested in the gray area, rather than in absolute black or white terms.
The scope of flexibility in rehabilitating neural wear also derives from the ability, though limited, of creating neurons in the brain in adulthood. Studies show that the support cells in the brain, which constitute the logistic infrastructure that supports the activity of neurons, have a potential ability to exchange their identity and turn into neurons due to the influence of certain regulation proteins that induce this transformation.
Most brain cells belong to the glia type of support cells. Some of them have the shape of a star, which is the source of their name—astroglia. At the early stages of brain development, the astroglia cells constitute a kind of reserve, and some of them become functional neurons. At later stages of development, the functional and structural transformation capability is lost. Researchers have found a way to reintroduce this magnificent past ability of structural and functional transformation, however, by clicking the buttons of the right genes.
It has far-reaching implications with respect to a future option of rehabilitating the neurons’ tissue following neural wear caused by various factors.
In 1868, Jules Cotard studied children who suffered from a serious brain disease that caused severe injury in the left hemisphere. Despite the injury, these children spoke normally. Hemispherectomy is a term that describes a surgery during which a whole brain hemisphere is removed. This extreme surgery is performed only as a last resort, mostly in people who suffer from brain injury in which one of the hemispheres generates repetitive electrical storms (epileptogenic zone) that severely impair life quality, and when all other treatment alternatives fail to bring about significant improvement.
Some children who underwent hemispherectomy, mostly due to repetitive convulsion episodes that could not be controlled by medications, managed to acquire almost full language skills. One of the famous cases in medical literature is of a girl who underwent surgery at the age of e
ight. Her left hemisphere was removed, but she managed to acquire good mastery of both Turkish and German. It seems that the significant brain flexibility during childhood enabled language skills to skip to the right hemisphere and find in it a neural infrastructure in which to settle.
One of the main causes of the gap between the high rehabilitative abilities of a child’s brain and the more limited abilities of an adult’s brain (the “recuperation gap”) derives from the fact that children’s brains are more flexible and plastic and have not yet accumulated core insights that are hostile toward incompatible new information. On the other hand, adults’ brains are, in this sense, “expert brains” with regard to world phenomena. They have reduced flexibility, and when they are damaged their rehabilitative potential is also reduced.
A Shining Path to Treatment—Electricity-Aided Therapeutic Approaches
Transcranial magnetic stimulation (TMS) is a therapeutic method designed to trigger a different action pattern in brain areas that suffer from malfunctioning; it’s delivered by means of magnetic fields. Through a ring of copper coil placed as a crown on the patient’s head, electrical current is transferred and induces the creation of a changing magnetic field. The changing magnetic field induces electrical current around it. This is a noninvasive method of triggering electrical currents in the neurons. This method is used to activate certain brain areas or, on the other hand, to block their activity. The triggering of neurons creates an “echoing cycle,” which continues to operate for a while, even after the triggering through the device has ended.
