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my lunch hour



I will start with disappointments, then work into the content matter. The title of the presentation is far out of context - it should have been "Fear and the Amygdala". The seminar started off by basically saying it was not at all going to deal with the mind/body issue - rather that through extensive study of fear, the presenter (Joseph E. LeDoux, PhD) was going to show how emotional response resulted as an effect of emotional stimulus. He defined emotional stimuli (an environmental occurance) which elicited an emotional response, and an emotional reaction. These are alikened to a reflex action, and a conscious reaction - your hand jumps off the hot pan handle before your mind "knows" it is hot. Emotional stimuli elicit a physical reaction about 30 milliseconds before the actual emotional reaction. Rather amazing, that things have been worked out to that level of detail.

Not exactly "Soul" but interesting work nonetheless.

Basically, what this research team has been doing (called the "Manhattan Project" because all the docs are located in NYC) is studying the physiological effects of fear stimulus (in a Pavlovian model) on all manner of animals, as it relates to the brain organelle known as the amygdala. Their findings go against the grain of historical findings on the matter, showing conclusive evidence which removes the so-called limbic system as the center of all emotional brain activity.

Until the past decade, much of psychology's answer to emotional "questions" as they pertained to brain chemistry lay under the magic umbrella forged by McLean in the depths of the 1950's. This sub-brain system, with the hippocampus as its "nucleus" supposedly explained the interaction of emotions as they relate to synaptic activity within the brain.

What LeDoux’s researchers have found is that, as far as patterned fear response is concerned, the amygdala, rather than the hippocampus is the center of neurobiological activity, as well as learning it seems.

Testing with rats, tones, and electric shock, LeDoux’s team was able to show the reaction of stimulated cells within the upper dorsal amygdala to a fear-inducing stimulus. Furthermore, in subdividing the amygdala, they showed which portions were responsible for reacting to brain excitation caused by external stimulus, as well as which were storage cells, which became programmed to respond to said stimuli after as few as three exposures. What I found amazing, is that this cellular organelle, as well as its patterned reactions, were modelled in anything in the animal kingdom, from sea snails, through all forms of vertebrates.

While there was some research on presynamptic plasticity, as well as variance of inter-neuron transmitter hypersensitivity, and interaction with other brain organelles, the findings in these follow-up queries were not nearly as significant as the conclusions drawn from this research’s central findings.

By understanding on a chemical level down to the sub-oranells, those areas of the brain involved in a fear response, there is incredible potential in the field of fear-therapy; most notably in dealing with OCD, PTST, and phobias. Furthermore, an understanding of how current therapies work, and how they can be improved are quickly ascertainable if the right research were to be applied to the footsteps of these findings.

Beyond that (in what I feel is the most important finding) is a new understanding of how learned-response seems to work in the brain. Less recent findings suggest the following model of activity on a cellular level:

Stimuli->Response->Storage

After initial imprinting, any time the stimuli are encountered, the working model was that the imprinted cells in storage were simply reacting in a preprogrammed manner. That is to say, the reaction they had to interneural transmitters, and what they themselves produced as a reaction to a particular current charge did not differ greatly after intial imprinting. The variance encountered was largely written off to differentials in the level of exposure, rather than the reaction of the storage cells.

The reality, however, seems to be that each time the stimulus is encountered, after the cellular activity peak in the upper-dorsal amygdala, that there is a retrieval, but also a chance for reprogramming. That is to say, the plasticity of the storage cells is not statically programmed, but rather, can be altered chemically based on the circumstances surrounding retrieval-transmission activity.

So what?

What this means, is that thresholds to learned fears can be lowered or heightened on a chemical level. There were suspicions of this, but no confirmations, as it seemed just as likely that therapy was simply strengthening another brain process to override a preprogrammed response, rather than changing the response at its root.

To me, this raises some strong questions as fear relates to sleep, especially nightmares (a pet research project of mine). I am wondering if nightmares might not be chemical echoes of activity in the amygdala – where the brain is essentially testing a programmed synaptic response against immaterial stimuli (generated by the subconscious) to maintain peak cellular plasticity in the face of a real stimulus.

Laymans: People are afraid of certain things by nature (heights, snakes, bugs, drowning etc) – other things are learned (guns, chainsaws, dynamite etc). In either case however, there is room to change the fear at its source, on a biological level. If that is the case, then nightmares are the reinforcing psychobiological method through which the brain maintains “peak fear reaction”, despite the fact that the fear stimuli may be noticeably absent from regular conscious stimuli.

This further draws me back into questions about dreaming, especially as to how it relates to the mind/body question. What are the regulatory systems which maintain this renforcing biological method? If the conclusion of my hypothesis is sound, there must be some greater pattern (perhaps within the hippocampal-amydalan pathways) which determines which stimuli need to be reinforced to maintain elasticity, and which are allowed to fade.

In a simple example, why do some people grow out of being afraid of something, and others are afraid of it their entire life? Chemically, based on the presentation I saw today, we know the “how” but are still pretty shady on the “why”.

Curiouser and curiouser, we meat puppets are.

Comments

( 2 comments — Leave a comment )
online_stalker
Jan. 8th, 2004 02:19 pm (UTC)
small horrible world
Joseph E. LeDoux, PhD

my brain shut down after reading that line because it is impossible for me to process an intelligent and articulate entry like this, but joe ledoux is a professor at the center for neural science at nyu, where i used to be a workstudy as i pursued my undergraduate degree. come christmas party time, he can really tie one on.

one of my responsibilities was paying his invoices for orders of animals on which to experiment. *cringe*

on a side note, while i was working there, i must have cataloged a thousand journals entitled "hippocampus" but i had absolutely no idea what that meant until i read your entry.
delascabezas
Jan. 8th, 2004 06:59 pm (UTC)
sick sad world indeed
he is still affiliated with nyu - you were probably finishing the orders for the research he was talking about today.
( 2 comments — Leave a comment )

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delascabezas
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