Just for the record, I would like to challenge anyone in the field of computer rendering/animation to reproduce the picture found in the link here, titled "Escher style Fractal - Connected Cubes" in three dimensions, and to make it viewable with the right eye glasses.
I have read eleven books about the brain -- some big, some little. The most useful and educational ones have plenty of redundant information in them but that just strengthens one's interpretations about what is read in the rest of those books, not to mention the articles and news items that contribute even more about the subject. I encourage anyone reading this to read as much about the brain as they can get their hands on to stimulate the myriad receptors in their own. There are some great articles on experimental data which should stimulate those regions of it which are intrigued in those who are naturally inclined to be curious.
For example, the cerebral cortex is a gray-hued sheet of brain cells measuring between a millimeter or two in thickness which covers the surface of the white matter which makes up the glial material which forms the scaffolding and structure which supports the neural networks which communicate with the central processing unit sitting on and surrounding the mid-brain. These constitute respectively the thinking and processing part of the brain. Most of the brain mass physically supports the network circuitry.
Scans which show activity when a subject is stimulated, such as the CAT (Computed Axial Tomography), MRI (Magnetic Resonance Imaging), fMRI (Functional Magnetic Resonance Imaging), PET (Positron Emission Tomography), SPECT (Single Photon Emission Computed Tomography), and DOT (Diffuse Optical Imaging) etc. tend to go a little deeper into the brain and display information when the neurons are activated, displaying the information transfer along the pathways and all the processes leading to where that information ends up. As to whether the actual information is stored or simply processed in the areas one speculates about is beyond the ability of scanning techniques to resolve or decipher.
This is where brain theory comes in. Not much is known for certain about the storage of information inside the brain but we do know the bio-electro-mechanics of information transfer via axons and dendrites and therefore we can draw some plausible conclusions. It may be that memory is an ongoing associative process whereby networks are reactivated on recall according to the original pattern of information processing when related information is received. An analogy to the brownian motion of atoms may be drawn. It is a motion that never ceases. Furthermore, the information pertaining to the visual imagery of the surface characteristics of objects that we see is modulated on all the particles which comprise the medium which transmits this information and we can draw an additional analogy from this fact, in that the information pertaining to imagery is retained as modulations reduced, or 'unrefined', to the molecular level and stored as patterns rather than as bits and bytes as in computer memory. In this way, the physical components of the brain can detach from the memory portions while still very much associated with them. Insomuch as it has been established to the satisfaction of many experts that an infinite amount of information can be stored on an electron the brain probably has infinite capacity for storage and different information can probably be stored within the same essential circuitry. As the association of experience recalls a memory the engram 'enlarges' into the unique pattern representing specific information.
In essence, while largely speculative, this idea limits the depth of the involvement at the quantum level of the process of memory and recall and which yet links that realm to the reality that we perceive at the macroscopic level. Nevertheless, a very definite analogy to quantum computing can be made, in that a qubit, or quantum bit, can assume all possible states at the same time. We are undeniably macroscopic representations, manifestations if you will, of quantum structures.
Tuesday, January 22, 2008
The brain encodes and decodes visual information
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.
I'd rather have a bottle in front of me than a frontal lobotomy
News Flash: A MRI study conducted by American researchers on 1,839 people who were categorized as abstainers, light drinkers, moderate drinkers, and heavy drinkers revealed that brain volume decreased with alcohol consumption. The decrease in volume was .25% for every increase in drinking category. Separate studies at University of North Carolina at Chapel Hill confirmed that alcohol has detrimental effects on brain functioning and cognition but Dr James Garbutt cautions that no studies have been done that show how brain volume and cognition are related and whether alcohol has any effect.
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I am reminded of the work of the late Dr. John Lorber, a neurology professor at the University of Sheffield in England. He used a CAT scan on a student who was referred by the campus doctor after being treated for a minor ailment because the doctor noticed that the student's head was slightly larger than normal. Lorber discovered that the student had virtually no brain. The student had about 1 mm of cerebral tissue clinging to the inside of the skull and about 1 cm at the top of his spinal column. The rest of the cranial cavity was filled with cerebral spinal fluid. He had the condition know as hydrocephalus, wherein the csf is prevented from normal circulation by being dammed up inside. The student had a measured IQ of 126, and graduated with honors from a mathematics program. Lorber went on to specialize in the study of people with hydrocephalus and developed case files on hundreds of individuals, many with "no detectable brain" and many measuring higher than average IQ's.
Then there is the work of Dr. Michael Gershon, professor of anatomy and cell biology at Columbia-Presbyterian Medical Center in New York, one of the founders of a new field of medical science known as "neurogastroenterology" and author of the book "The Second Brain". He re-examined studies first documented by a 19th century German neurologist by the name of Leopold Auerbach. Close examination of the nerves lining the esophagus, stomach and digestive tract reveals a complex network of neurons about the same in number as exist in the cerebral cortex. According to Dr. Gershon nearly every chemical that controls the brain in the head has been identified in the gut, including hormones and neurotransmitters. We have, in effect, a second brain in our enteric system.
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The brain in our head is made up of a thin layer of neurons up to two millimeters thick which follow the folds and creases of the outer brain and which comprise the cerebral cortex, or the gray matter. This is the thinking part of the brain. These neurons are networked via axons and dendrites through the glia, the white matter, to the mid brain, where information processing occurs. We could essentially do without the glia and fill that space with csf, which is basically the case with people who have hydrocephalus. The seriousness of that condition is entirely related to buildup of fluid causing pressure on the brain which can cause potentially fatal seizures, and this is why many of these patients have permanent shunts installed to drain the fluid to prevent the buildup of pressure, but their normal brain functioning is not normally impaired unless damage has occurred.
The studies relating alcohol consumption to reduction in brain volume did not specify whether this was the case for the entire brain or for the cerebral cortex. Studying cognitive impairment and brain functioning of people under the influence of alcohol need not be done in the laboratory. In any event, it's old news that the average person uses but a small amount of the full potential of their brain. That fact probably makes me a little more indifferent to the alcohol related study. That, and the bottle in front of me.
