This is a continuation of post #34, the first half of the book, numbers 16 and greater are the last part. I wanted to keep it all together and to remind myself as I complete my short (but detailed when needed) summary.
1. Mingling of two or more of the sensations (sight, sound, touch, taste, smell) in a cross modal fashion. Most commonly reported is color and hearing.
2. Synesthetic experience is constant and stable (same stimulus results in same response) for the most part. There is no known abnormal pathology known to it.
3. More women than men have it, or at least are reported to admit having it.
4. Seven of the forty two individuals studied by Cytowic had immediate relatives who had it, suggesting there is a genetic component to it.
5. There is no known agreement when those with mixed sensations of say color hearing when two individuals with that trait were compared, their experiences and descriptions were completely unique to the individual describing them.
6. Cytowic was impressed at how highly individualized the triggering stimuli usually are, explaining why the expression of synesthesia vary from person to person. It is an all or nothing trait, and some people seem to have it more than others.
7. Human imagination fill the gaps of those (without it) in trying to understand it. Those who experience it daily have trouble describing the "ineffable quality" of it, leading to bewilderment and confusion of those trying to grasp it. It must be experienced, and cannot be imparted or transferred to others.
6. Failure of tests for items 5 thru 7 above lead Cytowic to a more qualitative investigation of the triune brain, from the bottom up, from the primitive brain (brain stem structures), to the limbic system, and finally to the cortex to determine the origins) of the mixed sensations that those with syesthesia experience. Were one or more of these structures responsible, and if so which and why.
7. Cytowic designed and administered a series of tests designed to qualify what those people experiencing synesthesia were sensing, this result being what is known as "Form Constants", now believed to be a limited number of perceptual frameworks, that appear to be built into the nervous system and are probably part of our genetic heritage.
8. Synesthesia can be induced temporarily by those who use LSD. LSD exerts three physiological actions, two of which oppose one another. It enhances low-level synapses coming from the brainstem relay, the hypothalmus, and at the same time suppressing the synaptic connections between the hypothalmus and high brain areas. Third, LSD causes an overall alertness and enhancement of synaptic pathways to the limbic system, the part of the brain that gives meaning to events and is concerned with emotion and memory. This part is key, "by blocking the normal flow at a point before a unified experience is created, LSD makes it 'stick" at a detail of the perception, like when a phonograph needle skips and plays the same part of a record over and over.
9. Those with synesthasia have great memory for detail, and an indelible recollection of the synesthetic event itself.
10. Temporal Lobe Epilepsy (TLE) can result in the joining of the elements of smell, taste, vision, touch and hearing, memory and emotion and epileptic synesthesia occurs in four percent of TLE events. A personal observation here, compared to people with lifelong synesthesia I can imagine it must be very frightening to suddenly be barraged with a 'mingling of the senses", whereas people who have synesthesia are used to its stimuli and effects.
11. Cytowic and Dr David Stump, an expert in measuring brain metabolism, used a cerebral blood flow (CBF) technique in which a radioactive isotope of xeon (harmless inert gas) is used to identify what areas of the brain are processing, given the blood and glucose is being delivered and consumed, with a helmet device fitted with radiation detectors (16) measuring 16 different brain regions while the subject engages in a task, in this case one that induces a synesthesia response.
12. A baseline state was taken, then two tests were conducted, one to simply stimulate the patient with a stimuli that resulted in a synesthesia response, and the second test, this time adding amyl nitrate (to boost the synesthesia response).
All three tests, baseline, normal stimuli, and normal stimuli with amyl nitrate went smoothly each lasting about eight minutes.
13. Review of the data yielded the following: baseline, low flow for someone the patients age, normal stimuli resulted in the blood flow to the left hemisphere of the patients brain at 18% less than in the baseline, that's right, than in the baseline, Holy crap ! The amount of flow is three times below the accepted flow of a normal person's. This was the first time Dr Stump (who was stumped, pun intended) had ever seen a reduced flow during the activation task (in this case a stimuli that brings on the sensation of synesthesia). The same effect was observed when amyl nitrate was administered. Synesthesia does not occur in the cortex, basically it shuts down when it occurs. The energy is being stimulated in the limbic brain, in the area where zoobyshoe describes as the hippocampus, which up to now I was under the assumption has to do with the storing of new memories, which makes sense in that people with this trait are able to retrieve them in great detail. I just didn't realize that it may be an area where a mingling of the senses occur. One point to note, the limbic system is deep enough that its metabolic activity is beyond the range of the CBF test to detect it.
14. Drugs can either stimulate or block the effects of synesthetes as follows:
The human cortex as we will see later plays an important part in either enhancing or dulling the effect of synesthasia.
15. As a rule when the cortex is depressed (reduced blood flow results in enhanced synesthesia effects) and when stimulated (increased blood flow results in a dulling or blocking effect of the sensation), Amphetimines block or dull the effects of synesthesia, while alcohol and amyl nitrate enhance it.
16. In 1922 Max Planck's principle dictates that of all possible paths, the one selected is the one that uses the least possible energy.
17. The limbic system processes input quickly, enhances cortical processes, and by extensive reasoning, reduces entropy, acts on incomplete information, creates order from continuous and incoherent of sensations, this gives humans their esthetic capacity. This capacity to determine relevance is what makes us unpredictable and creative.
18. The brain stem and cerebellum provide an action component for motor output, the model of the world is contained in the cerebral cortex, while the critic lives in the limbic system.
I think I understand (basically two main concepts) so far, areas of the brain operate at different frequencies and when triggered by a visual, sound, smell, taste, or touch stimulus can cause other areas in the brain, (normally suppressed to everything but that stimulus) to create a near simultaneous activation in the brain which for most of us is silent because the adjacent processing area in the brain does not respond.
19. Cytowic in his afterward (page 243) published in 2003 puts the elaborate and at time simplified explanation to rest, in 2002, a functional MRI study by Julia Nunn confirmed what was long expected: V4 activation (without V1 or V2 activity(early visual areas)) in synesthetes who see color in response to spoken words. Whereas both synesthetes and controls activated auditory and language areas as expected, the synesthetes also activated the color area (V4), but only on the left--in agreement with earlier results. Such lateralization is tantalizing, given their color experiences were not confined to the right visual field. The fMRI technique, which is the most refined one we have to date, also disclosed activation in transmodal areas concerned with memory and affect, consistent with both the subjective statements and clinical observations of synesthetes.
An unexpected result of this study was when actually viewing colored surfaces, synesthetes don not activate their left V4, the area for color. Right V4 did function for both synesthetes and controls. Ordinarily viewing colors activates both right and left V4, as well as ealry visual areas V1 and V2. The implication therefore, is that participation of left V4 in synesthetic color experience renders it unavailable for color perception--in other words, synesthesia appears to have hijacked an existing brain function. This surprise is consistent with the observation that nonsynesthetes merely imagining colors (compared to performing a visual control task not involving color) do not activate V4, Thus the brain basis of synesthetic color experience is consistent with real color perception rather than color imagery. This refutes earlier criticisms that synesthetes are just "making it up" or have "overactive imaginations."
20. Most who study synesthesia now believe that inheriting an X-linked dominant genertic mutation results in failure in synesthetes' brains to prune juvenile projections between brain structures that normally exist temporariliy during the development of all brains. Everyone is born synesthetic, only to lose the capacity as the brain matures.
21. An exception to the people who have not had their brain structures pruned is when we are able to quiet the chatter of our cognitive mind. Roger Walsh of the University of California (2002) has evidence to support it. He says synesthasia is one hundred times more common in meditative states compared to baseline prevalence. With increasing levels of experience, the numbers who experience synesthesia increases (35% vs 63%). Even within the most inexperienced beginners groups those experiencing synesthesia had twice as much average practice time (17 years) than those who did not experience synesthesia (8 years). Among a third group who had between 24 to 31 years of practice, over half had polymodal experiences and also perceived categories synesthetically--thoughts, emtions, and images felt as a sensation. For all three groups, synesthesia was most apparent during meditation.
I will add the remaining information on the binding problem and the linking to metaphor and language tomorrow evening before the thread is no longer editable.
I hope you all have enjoyed this wild ride. I know I have.
P.S.
Here is some background info I was looking at while researching this post:
Here are a couple of useful videos for context:
http://www.youtube.com/watch?v=g6KpIrKCDwg"
I found this paper:
http://www.google.com/#hl=en&q=alph...&oq=alpha+frequ&gs_rfai=&fp=84c7fb41710deb10"
Rhody...
Zooby: Fixed #1, sorry I missed it. More this evening...
I have to say, the more I learn about the brain the less I understand. So much of it seemed to be localized, then diffuse, now it's a combination of the two. *boggle* Truly it's a marvelous organ and this disucssion in particular highlights both its plasticity, and as you say, the nature of what "triggers" a thought, or not.