baudrunner's space: The dynamics of memory
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Monday, January 21, 2008

The dynamics of memory

The mind's ability to recall memories has traditionally been one of the most puzzling of its features. Scientists are still in the process of completing their theories regarding the process by which memory engrams are stored and retrieved by the brain. Complex experiments have been conducted which conclude only that inhibitory and excitatory neural activity plays a major role in pattern recognition and that this therefore constitutes an important component in the process whereby memory engrams are constructed.

It has been determined that neurons in culture are dedicated to the task of inhibition or excitation and that their ratio is about 80% excitatory to 20% inhibitory. (Even though the experiment described in the Oxford Journal seems to suggest that single neurons can display both inhibitory and excitatory behaviour, it is difficult to obtain a reading from a single neuron by using electrodes and making those kinds of determinations from graphs of electrical responses to stimulus. Such determination is best achieved by analysing neural activity in vitro)

Recent experiments by researchers at Tel Aviv University in Israel shed some light on the complex task of pattern generation and memorization. They isolated neurons in cultures and treated the inhibitory neurons with gamma-aminobutyric acid (GABA), which was used to suppress the inhibitory mechanism. When stimulated, the excitatory neurons established a firing pattern which was maintained without intervention for an entire day. This pattern "coexisted with the electrical pattern that was spontaneously generated when the neural culture was initially linked." Furthermore, establishing another new pattern did not restrict the original firing sequences and the three patterns coexisted without interruption.

This experiment is important in that it demonstrates the parallel processing which the brain is capable of performing. Additionally, it may very well lead to the development of neural memory modules for computing applications. But its real value lies in the contribution toward developing a more comprehensive theory on just how the brain functions with respect to memory.

Simply imprinting a pattern does not guarantee long term memory (LTM). If disruption of the brain's attention occurs then retention fails. LTM requires at least five to ten minutes and up to one hour of associative neural activity and engram construction for retention or consolidation of new information to take place. There is every reason to believe that once established, the engram is permanent. Memory loss is the result of a break in the associative process whereby the brain attempts to retrieve the engram, usually caused by trauma or some type of degenerative brain condition.

It is association which restores the pattern of neural firing and allows memory recall to occur. This association may be in the form of visual cues or contextual cues that reassemble the pattern from thought. In my opinion, imagination results from the ready assembly of abstractions resulting from a conscious effort to establish an original firing pattern, and will always have its roots in established engram structure and recall through the associative process.

None of this actually explains just how the patterns are stored and how that storage is reinforced during the process. It isn't entirely inconceivable that neural firing patterns and firing pattern potential - a form of pattern compression in the amygdala and hippocampal areas - continues so long as we are alive. The Tel Aviv experiments lay the groundwork for that theory. We are no doubt consciously allocating priorities to certain memories which we are more likely to retain in long term storage. What is perhaps even more puzzling than remembering is what it is that generates the interest to do so in the first place.

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