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BLUEBLOCR
Social climber
joshua tree
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Jul 20, 2014 - 03:45pm PT
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but it will not tell you how your neurons produce the sensations you experience, or how other people's experience and thinking may differ from your own.
Here's agood answer per ur question,
found in Wiki, under fMRI.
Physiology
The brain does not store glucose, the primary source of its energy. When neurons go active, getting them back to their original (polarized) state requires actively pumping ions back and forth across the neuronal cell membranes. The energy for these motor pumps is produced from glucose. More blood flows in to transport more glucose, also bringing in more oxygen in the form of oxygenated hemoglobin molecules in red blood cells. This is from both a higher rate of blood flow and an expansion of blood vessels. The blood-flow change is localized to within 2 or 3 mm of where the neural activity is. Usually the brought-in oxygen is more than the oxygen consumed in burning glucose (it is not yet settled whether most glucose consumption is oxidative), and this causes a net decrease in dHb in that brain area's blood vessels. This changes the magnetic property of the blood, making it interfere less with the magnetization and its eventual decay induced by the MRI process.[17]
The cerebral blood flow (CBF) corresponds to the consumed glucose differently in different brain regions. Initial results show there is more inflow than consumption of glucose in regions such as the amygdala, basal ganglia, thalamus and cingulate cortex, all of which are recruited for fast responses. In regions that are more deliberative, such as the lateral frontal and lateral parietal lobes, it seems that incoming flow is less than consumption. This affects BOLD sensitivity.[18]
Hemoglobin differs in how it responds to magnetic fields, depending on whether it has a bound oxygen molecule. The dHb molecule is more attracted to magnetic fields. Hence, it distorts the surrounding magnetic field induced by an MRI scanner, causing the nuclei there to lose magnetization faster via the T2* decay. Thus MR pulse sequences sensitive to T2* show more MR signal where blood is highly oxygenated and less where it is not. This effect increases with the square of the strength of the magnetic field. The fMRI signal hence needs both a strong magnetic field (1.5 T or higher) and a pulse sequence such as EPI, which is sensitive to T2* contrast.[19]
The physiological blood-flow response largely decides the temporal sensitivity, that is how well we can measure when neurons are active, in BOLD fMRI. The basic time resolution parameter is the TR, which dictates how often a particular brain slice is excited and allowed to lose its magnetization. TRs could vary from the very short (500 ms) to the very long (3 s). For fMRI specifically, the hemodynamic response lasts over 10 seconds, rising multiplicatively (that is, as a proportion of current value), peaking at 4 to 6 seconds, and then falling multiplicatively. Changes in the blood-flow system, the vascular system, integrate responses to neuronal activity over time. Because this response is a smooth continuous function, sampling with ever-faster TRs does not help; it just gives more points on the response curve obtainable by simple linear interpolation anyway. Experimental paradigms such as staggering when a stimulus is presented at various trials can improve temporal resolution, but reduces the number of effective data points obtained.[20]
BOLD hemodynamic response
The change in the MR signal from neuronal activity is called the hemodynamic response (HDR). It lags the neuronal events triggering it by 1 to 2 seconds, since it takes that long for the vascular system to respond to the brain's need for glucose. From this point it typically rises to a peak at about 5 seconds after the stimulus. If the neurons keep firing, say from a continuous stimulus, the peak spreads to a flat plateau while the neurons stay active. After activity stops, the BOLD signal falls below the original level, the baseline, a phenomenon called the undershoot. Over time the signal recovers to the baseline. There is some evidence continuous metabolic requirements in a brain region contribute to the undershoot.[21]
The mechanism by which the neural system provides feedback to the vascular system of its need for more glucose is partly the release of glutamate as part of neuron firing. This glutamate affects nearby supporting cells, astrocytes, causing a change in calcium ion concentration. This, in turn, releases nitric oxide at the contact point of astrocytes and intermediate-sized blood vessels, the arterioles. Nitric oxide is a vasodilator causing arterioles to expand and draw in more blood.[22]
A single voxel's response signal over time is called its timecourse. Typically, the unwanted signal called the noise, from the scanner, random brain activity and similar elements, is as big as the signal itself. To eliminate these, fMRI studies repeat a stimulus presentation multiple times
Breaking it down in my layman's mind, if i were to talk in your ear. Would i in a sense, be Creating matter(the "meat brain") out of nothing? Well not nothing, sound waves to be exact.
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Ward Trotter
Trad climber
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Jul 20, 2014 - 03:54pm PT
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Free will is a question of whether or not a person consciously chooses an action or non-action unfettered from mechanically imposed constraints. It is pretty easy to find our for yourself how this all works, but you have to be willing to do a lot of quiet empirical observation and for many on this list, not only is this impossible or at any rate beyond them, they don't trust any observation sans measuring instruments.
But you haven't provided an answer or clarification to your "free will" entree, only that the putative answer as regards free will lies with your listeners willingness to engage in "empirical observation". That's a funny way of putting it Largo. I mean, what is saliently 'empirical' about meditatin' ? And , while were at it, what empirical protocol in general will lead us to an answer for the age-old enigma of free will?
Moreover, if free will exists outside of physical antecedents , from where does it arise? From a patient, breath-mediated ,entrained observation of one's subjective experience? From an as yet undefined or defined supernatural source? From whence?
I am not discounting non-physical antecedents out-of-hand--- I would just like to hear a few more that I may not already be aware of.
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BLUEBLOCR
Social climber
joshua tree
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Jul 20, 2014 - 04:46pm PT
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fMRI machines measure the blood flow in our brain's. The blood follows behind neuron activity to replenish energy to the worked neuron. Neuron activity is provoked,inspired, through our senses by way of the central nervous system. The CNS sends electrical pulses to the neuron, which inturn converts the pulse to "meat". We know we have information stored on the meat walls of a cell called DNA. Is the brain's memory stored in the same manner?
fMRI"s are a long ways from telling us what the brain is doing. They even cause more activity or noise than the sensory input. And they don't see what the brain is firstly doing, the electrical synapses. It merely see's the footprints of where they been..
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Ward Trotter
Trad climber
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Jul 20, 2014 - 05:11pm PT
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Is the brain's memory stored in the same manner?
I'm not a neuroscientist but I can let you know what I've learned:
In general memories are stored in groups of neurons that are primed to fire in more or less the same way as when they were originally formed . There are groups of neurons in your brain that are classified as "Mom" and were formed under unique circumstances , as well as being constantly updated. Whenever you think of mom those neurons fire in a distinct way , and do so by unique pathways, differentiated from say, "hydrogen bomb" which is stored by another group of neurons.
The exact processes are still under investigation. However part of the machinery as regards the original encoding of these neuron groups might have something to do with the brain's metabolic scenario as described in your pre-edited post. You know the bit about baseline and undershots, etc..
Furthermore, by just thinking of 'Mom' you reactivate those neurons which in turn sets in motion a series of housecleaning maintenance projects involving autophagic elimination of damaged cells, as well as minimizing amyloid plague deposition in your dendritic connections between cells. This of course reveals a "use it or lose it" scenario.
If the formation of plaque exceeds your ability to clean it up then you can run the risk of developing dementia or Alzheimer's , resulting in the loss of memory and a consequent inability to remember exactly who Mom is--- as distinct from "chair"
The reason for this is that the plaque interferes with the group of Mom neurons and their ability to communicate with one another. Therefore,your memory of Mom depends on the capacity of a particular group of neurons to be sociable with one another.
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jgill
Boulder climber
Colorado
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Jul 20, 2014 - 05:38pm PT
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Basucakky, where Tvash's belief crumbles is when one holds an open focus - and one can experience the "micro machinery" begging you to look at this thought or focus on this sensation or feelings or memory - and you don't . . . . This sounds lucidrous when stated like this, but when encountered in direct experience, it all gets clear in a flash. (JL)
Oh boy, I had a feeling that I would be told the only way to experience free will would be sitting on my butt staring at nothing. It hardly seems worth it. And, by the way, my romps with "I" consciousness satisfied "but when encountered in direct experience, it all gets clear in a flash." It would seem that if "I" is an illusion, then so is free will.
The simple examples JL gave about writing and free will were unpersuasive, but I should meditate on that.
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BASE104
Social climber
An Oil Field
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Jul 20, 2014 - 05:46pm PT
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It is refreshing to hear you guys discussing the physical brain. JL and his gang have constantly dismissed it as the "meat brain." This baffles me.
Neuroscience is an interesting area of study, with many questions and lots of observation taking place. Many of these observations cannot be dismissed.
The argument that there is some hidden spark, such as the religious notion of an eternal "soul," is where you step off of firm ground and venture into mysticism, spiritism, pseudo science, and pure guessing.
The reductionist, physical study, of the brains of humans, and thousands of species of animals, is bearing constant fruit. To dismiss this as irrelevant nonsense is a deeply flawed position.
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BLUEBLOCR
Social climber
joshua tree
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Jul 20, 2014 - 05:46pm PT
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Doesn't this sound like a means for storing info?
The mechanism by which the neural system provides feedback to the vascular system of its need for more glucose is partly the release of glutamate as part of neuron firing. This glutamate affects nearby supporting cells, astrocytes, causing a change in calcium ion concentration. This, in turn, releases nitric oxide at the contact point of astrocytes and intermediate-sized blood vessels, the arterioles. Nitric oxide is a vasodilator causing arterioles to expand and draw in more blood.[22]
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WBraun
climber
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Jul 20, 2014 - 06:01pm PT
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The argument that there is some hidden spark, such as the religious notion of an eternal "soul," is where you step off of firm ground
First of all it's not hidden at all.
You're vision is imperfect, perfect it and you'll see that you are not on firm ground ultimately.
Your knowledge is incomplete ......
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Ward Trotter
Trad climber
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Jul 20, 2014 - 06:01pm PT
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Doesn't this sound like a means for storing info?
Yes . If my memory serves me right (no pun intended) the glutamate system amounts to a general neurotransmission pathway. The complex pathways involving the cholinergic system and the precise interplay with the glutamate is still poorly understood.
Nitric Oxide is a messenger molecule in many processes involving memory formation.
Your body's main source for NO is the amino acid Arginine. NO is also responsible for male erections, and is important for the immune system. Certain immune cells use targeted puffs of NO to destroy pathogens---especially bacteria
It also moonlights as a constituent of smog--- again, if my memory serves me right.
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BLUEBLOCR
Social climber
joshua tree
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Jul 20, 2014 - 06:24pm PT
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NO is also responsible for male erections
That's interesting! i wonder if NO could be responsible in implementing the amount emotional significance to the specific experience or thought stored in memory?
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Ward Trotter
Trad climber
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Jul 20, 2014 - 06:36pm PT
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That's interesting! i wonder if NO could be responsible in implementing the amount emotional significance to the specific experience or thought stored in memory?
I don't know. Perhaps it has a role in vasodilation at precise moments . Just off the top of my head I do know that the emotional content of memories are partly stored or regulated by the Amygdala . (The brain's Limbic System)
In psychopaths for instance the Amygdala is known to be undersized--- resulting in a dysregulation of emotional content in processing memory; despite the core memory being otherwise unaffected.
BTW NO is responsible for erections at the site of the penis--- not in the brain.
http://www.human-memory.net/processes_storage.html
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BLUEBLOCR
Social climber
joshua tree
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Jul 20, 2014 - 06:52pm PT
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We definitely partake of experience or an idea bfore it becomes a memory!
Our bodys are a machine devised to measure sensory input and convert it to material dimensions for storage..
BB2014
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MH2
climber
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Jul 20, 2014 - 08:04pm PT
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A nice sample of your misunderstandings, JL.
We can easily see that a staunch physicalist position can never admit nor yet fathom a free choice because it would not, perforce, be biologically/mechanically imposed. (JL)
We make free choices all the time.
What's more, because ALL actions are based on preordained stimulus and uncouscious decision of the bio robot, stimulus and decisions ALL originate at a strictly biological level far below conscious thought. (JL)
Why "far below conscious thought?" Conscious and unconscious thought are in constant communication. There is no clear line between them.
What'ds more, conscious thoght is totally incapible of influencing the biological level, because the direction of influence only goes up (JL)
Hell, no. Conscious and unconscious thought loop around each other. Very very little in the brain only goes one way. Muscles send information back to the brain. The brain even sends messages OUT to sensory receptors. Within the brain everything is pretty much connected to everything else.
It appears that, in short, you object to biology because you think it rules out free will. No so. As BASE104 says, you can have systems which are deterministic but whose behavior cannot be predicted. How would you distinguish that from free will? For all practical purposes, human beings have what we think of as free will and have the ability to make choices which we cannot guess beforehand.
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BLUEBLOCR
Social climber
joshua tree
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Jul 20, 2014 - 09:44pm PT
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you can have systems which are deterministic but whose behavior cannot be predicted.
Are you talk'in biological systems? Can you say that about a cell? How about an acorn, or a fern? Aren't they predictable? what about an ant, or a whole colony? A fish, or a monkey? Are these deterministic systems? Are they not predictable?
What's an example of an unpredictable deterministic system?
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hashbro
Trad climber
Mental Physics........
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Jul 20, 2014 - 10:24pm PT
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"mind"
is nothing more than a human construct
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Tvash
climber
Seattle
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Jul 20, 2014 - 11:13pm PT
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a score of particles is all it takes
to make galaxies, whores, coffee and cakes
to make all that gives birth
four nucleotides will do
Thank God the sexes
were cut off at two
So why the surprise
when we up and suppose
that our sea monkey brains
lead us round by the nose
it feels like a play
but its only a movie
cuz our sea monkey brains
are keeping it groovy.
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BLUEBLOCR
Social climber
joshua tree
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Jul 21, 2014 - 12:08am PT
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^^^that poem couldn't have been predicted!
What happened to bushmans poem last night?
What'ya think about my theory that thought creates matter?
ii'll bet a cheeseburger somewhere in there "brainwaves" creates matter.
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MH2
climber
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Jul 21, 2014 - 08:28am PT
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I guess The Bard did not foresee man making a generation of killer robots and removing himself permanently from The Stage.
Don't worry about predictable versus not, BLUEBLOCR. Humans and other things do not fit easily into the boxes of our words. There is even a piece of rock, a moon of Saturn called Hyperion, whose motion is unpredictable even though only physical forces act on it. Simple physical systems can be unpredictable, and biological organisms are far far from simple.
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Tvash
climber
Seattle
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Jul 21, 2014 - 08:30am PT
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Chaos happens.
The problem here is that knowledge of probabilistic phenomena isn't evenly distributed.
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jgill
Boulder climber
Colorado
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Jul 21, 2014 - 10:44am PT
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For all practical purposes, human beings have what we think of as free will and have the ability to make choices which we cannot guess beforehand (MH2)
That's it in a nutshell. Even with decisions coming to us from "below" in a mechanistic manner, in practice we demonstrate free will. As for those deterministic systems with, practically speaking, unpredictable outcomes . . . weak emergence, once again:
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