Memory

Memory - the property of the Central nervous system to store and reproduce the traces of previous her excitations. The memory consists of three consecutive stages: 1) remembering events, 2) the preservation of their tracks and 3) reproduction of what is stored in the Central nervous system. There are two basic types of memory spontaneous and random. Involuntary memory is a passive process related to the ability of the Central nervous system to record tracks from influencing stimuli. In this case, before a person does not have a task to remember anything. Arbitrary memory associated with active processes in the Central nervous system, aimed at remembering certain specific material. It is the psychological Foundation of all learning. There are two forms of arbitrary memory: direct and indirect. The first is by repetition, were learned material and may be auditory, visual, motor. Indirect, or logic, memory is the most durable and capacious. Memorization of material in this case is due to its distribution in the system or using a specific code (formulas, charts, graphs). Involuntary memory is strongly developed in children, especially younger children. In adults paramount logical memory.
Duration of preservation of traces of the institution in the Central nervous system distinguish between short-term memory associated mainly with playback and recognition, and long-term memory associated with fixation in the Central nervous system with all of effects in the body.
Currently believe that memory is a function of a brain, but the man and highly organized animals were important elements of the cerebral cortex. In neurosurgical operations it was found that human memory impairment stands in direct dependence on the remote area of the cortex of the brain. Structural and functional basis of memory can be the formation of new nerve connections in the Central nervous system due to the growth processes of neurons and the formation of new synapses, or the formation of the closed neural circuits in which the excitation may circulate for a long time (short term memory). The learning process associated with the transition of short-term memory to long-term. Long-term memory is considered as a function of individual nerve cells. There intracellular the mechanism of long-term information storage in neuron associated with ribonucleic acid (RNA). Under the influence of the excitation pulses coming to the neuron, there is a change nucleotide composition RNA neurons in the result of the replacement of some other nucleotides. Modification of RNA molecules leads to the synthesis of other, different from the former, protein, which is a stable footprint remember. The number of possible permutations in a molecule of RNA is very large, easily preserve 1016 pieces of information - the likely number to a person over 70 years of life. Over time, more statistically likely changes in the molecule of RNA are being depleted and new combinations are only less likely changes. This helps to explain the specific changes in learning and memory in older people.

Memory is the property of the Central nervous system to capture, store and reproduce the traces of previous her excitations. Externally, the memory appears in recognition of the phenomena of the surrounding world and in their play. Psychologists studying mainly these manifestations of memory and its General properties both in norm and in pathology, artificially allocated three kinds P.: 1) the most simple and short is continued feeling; 2) direct, arbitrary; 3) indirect, or logical.
The first idea about localization., in the Central nervous system were obtained from the experiments conducted during neurosurgical operations. If irritation electric shock during operation temporal region of the cerebral cortex in patient arose the memories of his past life. The results of extirpate certain parts of the brain of animals in experiments in humans after neurosurgical operations showed that the deterioration P. depends on the size of the distal part, not on what exactly is the part of the brain udaljenim way, the practice of neurosurgery has allowed to conclude that the PA - diffuse the entire property of the cerebral cortex, although not all the areas of it are equal.


Fig. 1. Principal scheme of the mechanism of circulation of the excitation pulses on closed circuits of neurons underlying short-term memory.

On the question about the mechanisms of memory until recently did not exist any whole theory of precise understanding of the processes associated with P. conditioned reflex theory I. P. Pavlov and the theory of traces experienced dominants A. A. Ukhtomsky can be attributed to the first attempts physiological explanation of the mechanisms., In recent years the problem of P. received new lighting in connection with the development of Cybernetics, computer equipment, as well as subtle methods neurophysiological studies and success of molecular biology and biochemistry. Currently, P. person, as well as P. machines, divided into online (short-term) and long-term. Believe that the memory of the brain is associated with circulation of the excitation pulses on closed circuits of neurons (Fig. 1). Such closed circuit can stay in the system of hippocampal circle (see Subcortical functions)within which the excitation pulses could circulate. P. on the fact, the event object is saved as long as you continue this circulation. If this process continues long enough (30-50 minutes), the structures of protein molecules nerve cells come some changes that are material substratum long P. Modern neurophysiology has numerous experimental proof of the existence of intracellular mechanism of long-term information storage in the neuron.


Fig. 2. Scheme of intracellular mechanism of long-term memory and "memory" (Hideo): 1 - neuron, its kernel and RNA molecule; 2 and 3 - coming nerve impulses cause permutations of purine and pyrimidine bases in RNA molecule; 4 - a new RNA synthesizes different protein; 5 - coming nerve impulses cause the protein and neuron excited that corresponds to the process of "memoirs" (A - adenine, guanine, C - cytosine).

There is a hypothesis, according to which preserve traces of excitation depends on ribonucleic acid (RNA). The frequency of nerve impulses in this nerve cell, violates the ionic balance within it; as a result violated the stability of bases RNA molecules (Fig. 2). This is the phase of transition, unstable remember. In this phase in the molecule of RNA can be replaced with one another, which will increase its resistance to applicants with some frequency nerve impulses. Modification of RNA molecules leads to the synthesis of other, different from the previous protein that provides a stable phase of remembering. In the future, this protein can respond to the same frequency nerve signals pulses, which previously determined the modification of RNA. The reaction of the protein may be accompanied by its decay, stimulating the nerve cell, which in turn leads to the excitation of a network of neurons. This process underlies the "memories". The number of possible permutations bases in RNA molecules is so great that it can easily preserve 1015 pieces of information - the likely number to a person over 70 years of life. Over time, according to the statistics, more than likely changes in the molecule of RNA are being depleted and new combinations of memorized information only remain less likely changes. This helps to explain the specific changes in the ability to acquire new skills and memory in older people.
The stated views of the mechanisms of short-term and long-term memory allows us to understand the clinical manifestations of some of its disorders (see Amnesia). The transition short-P. in the long is the process of consolidation or consolidation. It is a very unstable process, since the circulation of excitation on neuronin circuits can be easily broken. If in the process of consolidation of the brain is exposed to strong electric irritation, chemicals (anesthesia) or mechanical trauma, the consolidation is broken and the person forgets the events immediately before impact (retrograde amnesia). If to the moment of impact of harmful agent consolidation process was completed, the information embodied in the structures of protein molecules, held very strongly. No compatible with life, physical or chemical factors, even cooling of the body to very low temperatures, have already unable to eradicate.
In the recent years was the hypothesis about the role of glial elements in the mechanisms of memory. According to this hypothesis nejroglialnyh elements are the Central organizing and programming system of the brain to provide a coherent actions of neurons. Now it is possible to consider, that in a basis of the mechanisms of memory lie molecular processes unfolding in the "nerve cell - glia".