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AD. He located and delineated various anatomical and physiological structures and made further
investigations into the function and structure of the nervous system.
Like the later Greeks, he assumed that memory and mental processes were part of the lower order of
animal spirits. He thought that these spirits were manufactured in the sides of the brain and that,
consequently, memory was seated there. Galen thought that air was sucked into the brain and mixed
with the vital spirits. This mixture produced animal spirits that were pushed down through the nervous
system, enabling humans to experience sensation.
Galen's ideas on memory were rapidly accepted and condoned by the church, which at this time was
beginning to exert a great influence. His ideas became doctrine, and as a result little progress was
made in the field for 1500 years. These intellectual strictures stifled some of the greatest minds that
philosophy and science have produced. In the fourth century AD St. Augustine accepted the church's
idea that memory was a function of the soul and that the soul was located in the brain. He never
expanded on the anatomical aspects of these ideas.
From the time of St. Augustine until the seventeenth century there were almost no significant
developments, and even in the seventeenth century new ideas were restricted by doctrine. Even so
great a thinker as Descartes accepted Galen's basic ideas, although he thought that animal spirits were
sent from the pineal gland on special courses could be triggered.
The more clear-cut these courses, the more readily, he thought, would they open when animal spirits
travelled through them. It was in this way that he explained the improvement of memory and the
development of what are known as memory traces. A memory trace is a physical change in the
nervous system that was not present before learning. The trace enables us to recall.
Another great philosopher, who went along with the tide, was Thomas Hobbes, who discussed and
considered the idea of memory but contributed little to what had already been said. He agreed with
Aristotle's ideas, rejecting nonphysical explanations of memory. He did not, however, specify the real
nature of memory, nor did he make any significant attempts to locate it accurately.
It is evident from the theories of the seventeenth-century intellectuals that the inhibiting influence of
Galen and the church had been profound. Practically all these great thinkers accepted without question
primitive ideas on memory.
50
Transitional Period  the Eighteenth Century
One of the first thinkers to be influenced by the Renaissance and by the ideas of Newton was David
Hartley, who developed the vibratory theory of memory. Applying Newton's ideas on vibrating
particles, Hartley suggested that there were memory vibrations in the brain that began before birth.
New sensations modified existing vibrations in degree, kind, place and direction. After being
influenced by a new sensation, vibrations quickly returned to their natural state. But if the same
sensation appeared again, the vibrations took a little longer to return.
This progression would finally result in the vibrations remaining in their 'new' state, and a memory
trace was thus established.
Other major thinkers of this period included Zanotti, who was the first to link electrical forces with
brain functions, and Bonnet, who developed the ideas of Hartley in relation to the flexibility of nerve
fibres. He felt that the more often nerves were used, the more easily they vibrated, and the better
memory would be.
The theories of these men were more sophisticated than previous ones because they had been largely
influenced by developments in related scientific fields. This interaction of ideas laid the groundwork
for some of the modern theories of memory.
The Nineteenth Century
With the development of science in Germany in the nineteenth century, some important advances
occurred. Many of the ideas initiated by the Greeks were overthrown, and work on memory expanded
to include the biological sciences.
Georg Prochaska, a Czech physiologist, finally and irrevocably rejected the age-old idea of animal
spirits on the grounds that it had no scientific basis and that there was no evidence to support it. He
felt that limited existing knowledge made speculation on the location of memory in the brain a waste
of time. 'Spatial localisation may be possible,' he said, 'but we just do not Know enough at the moment
to make it a useful idea'. It was not for some fifty years that localising the area of memory function
became a useful pursuit.
Another major theory presented in this century was that of Pierre Flourens, a French physiologist,
who 'located' the memory in every part of the brain. He said that the brain acted as a whole and could
not be considered as the interaction of elementary parts.
Modern Theories
Developments in memory research have been aided to an enormous degree by advances in technology
and methodology. Almost without exception psychologists and other thinkers in this field agree that
memory is located in the cerebrum, which is the large area of the brain covering the surface of the
cortex. Even today, however, the exact localization of memory areas is proving a difficult task, as is
the accurate understanding of the function of memory itself.
Current thought has progressed from Hermann Ebbinghaus's work, at the turn of the century, with
regard to basic learning and forgetting curves, to advanced and complex theories. Research and theory
can be roughly divided into three main areas: work on establishing a biochemical basis for memory;
theories suggesting that memory can no longer be considered as a single process but must be broken [ Pobierz całość w formacie PDF ]