Showing posts with label Theory of Neurophysiology. Show all posts
Showing posts with label Theory of Neurophysiology. Show all posts

Saturday, February 7, 2009

Neurophysiology of Learning

By Farzana Bukhari

1. Definition of Neurophysiology and learning
2. Historical background
3. The nerve cell
4. Thy synapse........
All the or none principle..
5. General structure of central nervous system ........
a. Parts of Brain.............................
b. Four lobes of cerebral hemisphere...............
c. Afferent and Efferent nerve tracts...................
6. Level of Arousal and the arousal system...........
7. Delays in nervous system and mediating process.......
8. Fatigue..................................
9. The Autonomic nervous system...............
10. Neurological patents...............................
11. Consolidation of memory traces.............
a. Types of memory with relation to time.........
12. Capacity, practice, motivation, understanding,

transfer of learning and training, forgetting.


Neuro Physiology.
Neuro means nervous system, physiology means function. So neurophysiology means function of the nervous system.

Learning can be defined as any relatively permanent change in behaviour which occurs as a result of practice or experience.

In early 19th century it was found that when a nerve is stimulated the result is muscle contraction. All this function is carried out by a single basic structural and functional unit of the nervous system called neuron.
Thorndike discovered the relation between behaviour and learning. According to him behaviour is to be considered a result of connections between stimuli and responses. And learning was a matter of developing new stimulus response connection.

The nerve cell:
b. Nerve cell is basic unit of nervous system.
c. It consists of following three parts.
i. Dendrites ii. Axon iii. Cell body
I. Dendrites: It is a root like structure provide connection with the other neuron.
II. Axon: It is that part of neuron which serves the function of transmission of message from neuron to muscle.
III. Cell body: It consists of the protoplasm with a central
nucleus. Which serves the function of control room of neuron.
In all these parts the recovery of damage is possible with dendrites and impossible with Axon and cell body

The synapse:
One nerve cell, does not actually join another nerve cell. The membrance of one nerve cell isolate it from the next. There are, however, places where the axon of one cell comes into contact with the dendrites of another cell or with the other cell body it self. This point of contact is known as a “synapse”.
At this place the axon or branches of the axon grow tiny knobs, which can be seen under high-powered microscopes. It is believed that these knobs play an important role in the transmission of nerve impulses from one cell to another.
Transmission at the synapse may be from the axon of one cell to the dendrites of another, or it may be from the axon of the one cell to the cell body of another.
The process of transmission is very slow and uncertain. And there is possibility that the impulse started in the dendrites may fade out before it reaches the cell body, and hence may fail to fire the cell.
The all or none principle: In the axon of nerve cell, firing takes place on an all-or-none principle. This means that if a nerve impulse is transmitted down the axon, then a full-size impulse is always transmitted. It is impossible to transmit half-size impulses by providing some rather weak stimulus to the nerve cell. This is known as all-or-none principle, which has certain important implications for the way the nerve system operates. If a sense organ is stimulated first with a weak stimulus and then with a strong one, the weak one does not produce the smaller impulse than the stronger one. Both produce nerve impulse of equal size.
However the stronger source of stimulation produces a greater number of impulses per second than does the weaker one. Intensity of stimulation is translated in the nervous system into frequency of nerve impulse. A strong stimulus in contrast to a weak stimulus also has another effect. It may excite more nerve cells and thus produce a greater volley of nerve impulse.
General structure of central nervous system:
Two main parts.
Spinal Cord
There are three layers in the body.
a. Ectoderm
b. Mesoderm
c. Endoderm.
Brain and spinal cord are Ectodermal derivative:;

Brain is divided into three parts:
1. Fore Brain: Cerebral hemisphere
2. Mid Brain:
Nucli e.g.
Red nucleus
Communicating point between fore brain & hind brain.
3. Hind Brain:
Medulla oblongata

Each hemisphere has four lobes. Each lobe is further divided by elevation (gyrus) depresion (Sulcus)
1. Frontal lobe:
* Thinking
* Behaviour (general)
* Abstract thinking.

2. Parietal lobe:
* Speech
* Hearing
* Skilled movement e.g.
* Writing and Sewing etc.

3. Temporal lobe:
* Behaviour (specific)
* Emotions

4. Occipital lobe
* Vision

Central Salcus – A demarcation point between motor area (efferent) and sensory area (afferent).

Attention/concentration of motivation are specified function of cerebral hemisphere.
· Each cerebral hemisphere has lobes, with specific function

Afferent nerves are those nerves which carry the sensory information from the sense organ like eye, ears, skin, nose and vision to the primary sensory areas in the brain, which is located posterior to the central sulcus.
Efferent are those tracts which starts from the motor areas in the brain to the sense organs. These tracts transmit information from the brain to the rest of the body.
Arousal system operates on at the following three sites.
1) Cerebral hemispheres.
2) Thalamus
3) Reticular activating system (RAS)

Common observation indicates that a person varies from time to time is likelihood of producing a response. When one is waiting for a visitor, the slightest sound of footsteps on the sidewalk outside the house will alert him in readiness to greet the visitor, but when one is relaxing on Sunday afternoon, similar sounds may go unnoticed. In the one case the nervous system is in a higher state of arousal than in the other. During sleep, the arousal level is at a minimum.
One must suppose that built into the brain is some system which can initiate and maintain arousal. One possible system would be a circular activity between the cortex of the brain and some of the lower centers. If this were so, then the lower centers could stimulate the cortex, and the cortex could in turn stimulate the lower centers. The arousal system may be to some extent dependent on external stimulation for its activity, but it must have some capacity for initiating activity; otherwise arousal would stop as soon as stimulation stopped, and the individual would fall asleep. Clearly this is not so, for we may remain a high level of arousal even when outside stimulation falls to a very low level.
Berger discovered that when an individual is in a waking state but relaxed and not attending to anything in particular, his brain produces changes in electrical potential at about the rate of ten cycles persecond. This rhythm, which rapidly disappears when he becomes active and starts to solve a problem, is known as the “alpha rhythm,” and its presence or absence is of considerable importance in the diagnosis of brain disorders.
When the person ceases to be passive but, say, is asked to solve some simple arithmetical problem, the rhythm tends to disappear In technical terms it can be said that the higher the state of arousal of the individual, the less marked is the alpha rhythm. In its place there appears a new, but less marked, rhythm with faster frequencies, known as the “beta rhythm.
What this means in behavioral terms is that when the brain is relatively inactive, insofar as the production of behavior is concerned, the cells work together synchronously In contrast, during activity they tend work on an individual basis and to fire a synchronously that is, groups of cells containing considerable numbers cease to he active together.
Bindra (1959) proposes two generalizations which summarize much that is known about the operation of the arousal system in relation to learning. His first generalization is as follows.
1. There is an optimum range of level of arousal within which a given measure of performance will reach its highest (or lowest) value; the greater the deviation in either direction from the optimum arousal level, the greater will be the decrease (or increase) in the performance measure.
2. With increased practice at performing an activity or task (i.e., with increased habit strength of a response), there is an increase in the range of the optimal level of arousal, as well as the range within which the activity occurs at all.

When the professor asks the student, “What is the numerical value of sine 45°?” the student pauses and then, after a few seconds’ delay, gives his answer. Thinking processes produce delays, and we may well ask what kind of neural processes could account for such delays. It is clear that some kind of processes must occur between the afferent inputs into the central nervous system and the occurrence of the different outputs, and these processes are known as “mediating” processes
· First there is the fact that different nerve fibers conduct impulses at different speed.
· Second, some delay occurs each time an impulse traveling down one nerve cell arrives at a synapse and activates another nerve cell.
· Since impulses travel at a high speed it is probable that the impulse would return to the point from which it started before that section of the loop and had time to recover and transmit the impulse again around the loop. If at that point a second loop were available the impulse might then travel around this second loop.

Such a system of loop is known cell assembly.
Hebb (1949) also relates the theory of the cell assembly to the process of learning in another way. He suggests that the establishment of the cell assemblies corresponds to the early learning process. The difficulty of the blind adult who gains vision for the first time is that he has no cell assemblies related to visual perception which enable him to interpret his percepts. His first task in learning to use visual cues involves the establishment of cell assemblies which permit him to recognize elements in his visual field.
Hebb suggests that the establishment of these assemblies is a very slow process, which accounts for the fact that early learning takes place at such a slow speed. However, once the assemblies have been established, learning of complex functions dependent upon them moves ahead at a rapid pace. These more advanced, or late, learning activities involve the development of connections between assemblies so that, a whole series of assemblies may become activated in sequence. While this theory has considerable elegance and fits the facts quite well, the evidence which supports it is indirect.
In order to obtain a partial understanding the student must first become familiar with certain related facts.
· First, nerves do not become fatigued through prolonged and repeated stimulation. Each time a nerve is stimulated and transmits impulse, there is a very brief period which follows, known as the refractory period, during which another impulse cannot be transmitted. At the end of this very short period recovery is complete, and the nerve ready to transmit another impulse. Repeated stimulation does not produce a state of fatigue in which the nerve .is unable to transmit an impulse for several second, minutes or hours. Nervous fatigue, as a condition depressed nervous activity resulting from excessive activity and the accumulation of by-products, does not occur).
· Second’, muscles can show fatigue. After a muscle has been frequently and strongly stimulated through the nerve, a time will come when further stimulation shows a very weak level of activity. Try doing push-ups, and the time will soon come when we cannot raise ourselves off the floor. In such a situation we would commonly say that our muscles were tired. Actually the difficulty is not muscular fatigue, but fatigue at the point where the nerve joins the muscle. Nervous impulses become blocked at that point and fail to activate the muscle).
· Third, inhibitory processes in the nervous system tend to set in after a given activity has been pursued for a time. After a person has studied a book, say on history, for a long period of time, the point is reached where a chance of activity is so that. It is larger for this reason that vacations are taken, to break the monotony of the daily routine.

It is a system of fight and flight. It is an automatic system which is not under the control of will.
There are two components:
* Sympathetic nervous system
* Para-sympathetic nervous system.

Structurally it consists of:
* Hypothalamus and
* Ganglia

Features of sympathetic nervous system: It is characterized by the following features.
It rises blood pressure.
It causes stimulation of the heart rate.
Decrease peristalsis
Pupilary dilation.
Hyper tention.
Features of parasympathetic
Decreased heart rate.
Hypotention (low blood pressure).
Miosis (Pupilary constriction)
Palmar Sweating (sweating of hands).
When a person under goes a surgical operation for epileptic focus in the temporal lobe then after surgery the patient has retrograde amnesia (loss of memory). All this memory process is controlled by a structure called hippo-campus. The amnesia is temporary and complete recovery is possible.
Leaning is the product of activity. The more you perform an action, the more you learn about that. While memory is a quality of the brain which is related with the hippocampus area. The loss of memory is called amnesia. While the disturbance of memory is called dementia.
The learning / activity is controlled by the parietal lobe of the brain. Similarly the memory center is located in the hippocampal area of the temporal lobe.
Recent memory: It is also called the immediate memory related with the present circumstances. And it is usually detected by objective finding disturbance and forget fullness for recent events.
Remote memory: This type of memory is determined by looking into the events performed / experienced in the past.Some of the abnormal mental conditions like psychosis, Chischizophernia, sever depression, catatonia can be treated / controlled with external cerebral stimulation (ECT). In this procedure the memory is disturbed so the primary problem is forgotten and the behavioural therapy can be administered with better results. Duncan (1949), had done experiments or rats. In this experiment ECT given to a rat soon after a learning trial interferes with its performance of the appropriate habit when it is tested the next day after recovery from the short lived convulsion

After knowing about the structure and functions of brain and role of nerves. We can say that human has a great power of brain which enable him to learn more and more but it depends upon his environment, that what kind of stimuli is present in it.
Teaching skills, classroom environment and presence of physical facilities in classroom of private schools and public schools.
In both schools students have same neurophysiology but it depends upon stimuli which are provided to them.

There is a mechanism in human’s brain which is performs function in different situations of revard punishment and at Atousal level. Motivation has a greater role in teaching learning process.
According to neurophysiology stimuli motivate and stimulate an organism to behave and respond.
In classroom situation:
When a student shows good performance in classroom e.g., during teaching learning process, behave good, actively communicate with teacher and group fellows. The teacher will appreciate him and this appreciation will motivate him for more better performance.
A student who show low performance in classroom will punished by teacher. And this punishment will motivate him to improve his or her self.
During teaching learning process when teacher ask the questions and invites the students to participates and communicate. So he arouses the students and motivate them for learning.
The role of understanding is minimized, not because it is undemonstrable, but because it grown out of earlier habits. The best way to get understanding is to build a body of connections appropriate to that understanding. When situations are understood at once, it is matter of transfer or assimilation, that is, there are enough elements in common with old situations to permit old habits to be used appropriately.
Transfer of training was defined through a statement from McGeogh and Irion, which follows: “Transfer of training occuts when ever the existence of a previously established habit has an influence upon the acquisition, performance, or relearning of a second habit”.
As for as neurophysiology of learning is concern we can say that human learn through stimulated response connection and after cell assembly he is able to respond better towards different and difficult stimuli.
For example:
Teacher is teaching maths at secondary level.:
He: Explain formula No – 1 (a+b)2
(a+b) 2 = a2 + b2 + 2ab.
1. Transfer of learning: (x+y)2
=(7+3) 2
=(2s+9b) 2
2. Transfer of training:
=(a – b) 2
= a2 – 2ab + b2
(a+b+c) 2
= a2 +b2 + c2 – ab – bc - ca

Forgetting as a fading process.
Forgetting as a repression process
Forgetting as an interference
Forgetting as an extinction process.

Hilgard R.Ernest Theories of Learning
Morgan, King, Robinson, 6th Edition Introduction to psychology
Travers M.W. Robert Essentials of Learning.