Neuroplasticity
Neuroplasticity refers to the brain’s ability to remap itself in response to experience. The theory was first proposed by Psychologist William James who stated “Organic matter, especially nervous tissue, seems endowed with a very extraordinary degree of plasticity". Simply put, the brain has the ability to change. He used the word plasticity to identify the degree of difficulty involved in the process of change. He defined plasticity as "...the possession of a structure weak enough to yield to an influence, but strong enough not to yield all at once" (James, 1890).
Biology
The brain consists of both neurons and glia cells. The neurons, which are cells housed in a cell body called a Soma, have branches which extend from them, referred to as dendrites. From these dendrites extend axons which send and receive impulses, ending at junction points called synapses. It is at these synapse points that the transfer of information takes place.
At the heart of Neuroplasticity is the idea of synaptic pruning. It is the ability to prune away unused connections, as well as to form new connections. The term is probably best explained in the aphorism, “Neurons that fire together, wire together” (Doidge, 2007, p. 63). The idea being that if two or more neurons fire simultaneously on a continual basis, they will eventually fire on the same cortical map, thus strengthening the connection. The reverse is true in that if two or more neurons begin firing separately, they will eventually form separate cortical maps. In the words of Donald Hebb:
"The general idea is an old one, that any two cells or systems of cells that are repeatedly active at the same time will tend to become 'associated', so that activity in one facilita...
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Two ideas about the nervous system that can be better understood from these observations are the concepts of having and locating the I-function. It seems that the I-function here is very often affected in terms of voluntary movement. A person with Arnold-Chiari malformation who has lost the feeling in and control of his arm for example will not be able to move it even upon someone's request and his or her own desire to do so. Some use of the I-function is definitely impaired. However, these observations do not seem to necessarily imply that some part of the I-function was damaged, because it may very well be located elsewhere- connections may have simply been lost. A person with Arnold-Chiari can still think and have a sense of self, but somehow can not connect with the various body parts that can be affected. Some uses and pathways of the I-function can be understood, but the exact location of it remains vague.
Carr mentions the affect that technology has on the neurological processes of the brain. Plasticity is described as the brains response through neurological pathways through experiences. The brain regions “change with experience, circumstance, and need” (29). Brain plasticity also responds to experiences that cause damage to the nervous system. Carr explains that injuries in accidents “reveal how extensively the brain can reorganize itself” (29).I have heard stories in which amputees are said to have a reaction to their amputated limb; it is known as a phantom limb. These types of studies are instrumental in supporting the claim that the brain can be restructured. Carr asserts that the internet is restructuring our brains while citing the brain plasticity experiments and studies done by other scientists. I have experienced this because I feel like by brain has become accustomed to activities that I do on a regular basis. For example, I rarely realize that I am driving when coming to school because I am used to driving on a specific route.
Scientists are on the brink of doing the unthinkable-replenishing the brains of people who have suffered strokes or head injuries to make them whole again. If that is not astonishing enough, they think they may be able to reverse paralysis. The door is at last open to lifting the terrifying sentence these disorders still decree-loss of physical function, cognitive skills, memory, and personality.
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The neurons or brain cells are shaped like trees. Young brain cells, called soma, resemble an acorn or small seed of a tree. The seed sprouts limbs when stimulated, called dendrites. Further on in development, the cell will grow a trunk like structure called an axon. The axon has an outer shell, like the bark of a tree, called the myelin sheath. Finally, at the base of the cell, there are root-like structures called axon terminal bulbs. Through these bulbs and the dendrite of another cell, cells communicate with each other through electrochemical impulses. These impulses cause the dendrites to
According to Hebbian theory, “neurons that fire together wire together” which can shape the organization of the brain and allow for neuroplasticity. If there is random distribution of processing, then there will be random pathways and organizations of the brain. This can’t be true considering what we know about neuroplasticity, which is not random. There must be a more purposeful integration or distribution across the brain to account for way the brain is organized. According to many brain lesion studies, it seems that the brain has compensatory strategies for certain functions in the event there is failure in some part of the brain. This suggests to me, that although there are unstable pathways that change all the time, they can’t be changing randomly. I believe Dennett & Kinsbourne (1992) should revise or clarify what they mean by random distribution and perhaps suggest a mechanism to support it with real life
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The nervous system is the most complex part of the body, as they govern our thoughts, feelings, and bodily functions. It is an important factor in science because it can lead to new discoveries for cures or diseases. The studies of the nervous system helped lower death rates from heart disease, stroke, accidents, etc. The nervous system is a network of neurons (nerve cells that sends information to the brain to be analyzed.
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The reason for the formation of these connections were to compensate for the loss of a sense, and to maximize the use of every region of the brain. However, once a sense is regained, will these connections still be necessary and thus persist, or will they be subject to neural pruning? If the newly synthesized connections are removed once a sense is regained, this could further suggest that the main mechanism behind cross-modal plasticity is visual or auditory deprivation, rather than increased experience with other senses. On the other hand, if the cross-modal connections are preserved, if would be interesting to do a follow-up study and see how the two connected sensory cortices might interfere with each other, leading to distorted perception. For example, if connections are made between the temporal and occipital cortex and vision is restored to a patient undergoing visual surgery, will the patient’s occipital cortex still respond to auditory stimuli and produce interferences with
Neurons and glia (cells that support neurons) are specialized cells for electrical signaling over long distances. Understanding neuronal structure is important for understanding neuronal function.
Increasing amount of research in recent years has added to developing knowledge of phantom limb pain (PLP). In this research proposal I aim to test the mirror therapy as an effective treatment in PLP. Phantom limb pain occurs in at least 90% of limb amputees. PLP may be stimulated by disconnection between visual feedback and proprioceptive representations of the amputated limb. Therefore, I will research both the neurobiology behind this phenomenon and whether illusions and/or imagery of movement of the amputated limb (mirror therapy) is effective in alleviating PLP of lower limbs. Mirror therapy has been used with noted success in patients who have had upper body amputation, but has not been determined in lower limb amputations. I would like to identify if form of treatment is equally effective in lower limb amputations. Yet, to consider mirror therapy as an effective means of treatment, one must understand PLP in its entirety. The main concern being if a limb is no longer attached to the body, how can neurons in the limb transport signals to the nervous system in order for the body to detect sensations? The biological significance of this project is to determine what occurs on the sensory level to cause PLP. Once that is discovered we can address whether or not mirror therapy is a plausible form of treatment.
"Patterns of activity in small, more primitive areas of the brain are recapitulated in larger, more advanced parts," Sutton says. "This means that nature did not have to develop new rules of operation for different levels of the brain from small clusters of cells to large systems."
The most basic elements of a neural network, the artificial neurons, are modeled after the neurons of the brain. The "real" neuron is composed of four parts: the dendrites, soma, axon, and the synapse. The dendrites receive input from other neuron's synapses, the soma processes the information received, the axon carries the action potential which fires the neuron when a threshold is breached, and the synapse is where the neuron sends its output, which are in the form of neurotransmitters, to the dendrites of other neurons. Each neuron in the human brain can connect with up to 200,000 other neurons. The power and processing of the human brain comes from multitude of these basic components and the many thousands of connections between them.