Physiological mechanisms
underlying the basic functions of the central nervous system

Conditioned-Reflex Theory of Memory

Posted: December 1st, 2009 | Filed under: Memory | Tags: , , , , , , , | No Comments »

According to the second theory of memory, the process of remembering involves the formation of a new system and the building of new links between the nerve cells. Can these potential nerve contacts last throughout man’s life? Can the fading of memory in old age (the ability to remember new events diminishes) be accounted for by the fact that the reserves of the nervous system are exhausted by that time? Mathematicians cannot throw any light on the subject. However, taking into consideration that any nerve cell receives several thousand nerve endings, it is very likely that the nerve network of human brain is capable of storing all the information required.

An argument in favour of this theory is that the nerve cells themselves have changed very little in the course of evolution. The biochemical processes occurring in the neurons of lower animals and man are very similar. Progress has mainly been made in the increase in the number of nerve cells and the improved organization of the nervous system.

Not everything that we know about memory at present corroborates this theory. If the larva of an insect, for example, of a flour beetle, is trained to turn only to the right when moving in a labyrinth, the adult beetle witl retain this habit. Hence, its memory has not been disturbed in spite of the fact that, when the larva changes into the pupa, its body structure changes, and all the nerve contacts and 90 per cent of nerve cells are destroyed. It remains a mystery how its memory is preserved.

At present it is difficult to say which of memory theories is correct. But, as to a conditioned-reflex memory, there is a unanimous opinion that temporary connections exist between the nerve centers, which retain recollections caused by a conditioned stimulus, and a command point governing the responses to it. However, this still leaves a lot to be explained. How this connection is formed is obscure. Some scientists claim that this bond is purely functional and merely transmits excitation more efficiently through certain synapses. Others consider that the formation of conditioned reflexes is accompanied by the appearance of new contacts between the neurons due either to the growth of their processes or of new synaptic formations on these processes.