Sunday, November 25, 2007

Habituation and Post Traumatic Memory Alterations

In the book, In Search Of Memory, Kandel discusses methods of Habituation, Sensitization, and Conditioning (pg 167). Habituation is when a subject is exposed to a stimulus so repeatedly and consistently that the subject grows accustomed to the stimulus and eventually begins to ignore it. This is something that we do many times throughout our lives. An example of how habituation to stimuli in our environment that might otherwise seem threatening can be seen through a wild animal’s reaction to a car opposed to a dog’s reaction to a car. Kandel writes about habituation that it “eliminates inappropriate or exaggerated defensive responses.” The dog no longer responds defensively to a speeding car, or in a large city, maybe even to a car horn which it encounters countless times a day. To habituation to something means to classify it as mundane and unworthy of notability. We are habituated to every rustle of the leaves that doesn’t seem abnormal. Without habituation we would be constantly unable to distinguish the important from the unimportant stimuli. Our reactions might commonly be inappropriately reactionary. We would live in a constant state of discomfort. Through habituation we achieve a level of stability in our world of expectations.

Though this stability and comfort we have learned to be shocked by what is unpredictable and new. If a situation arises which is extremely shocking and negative our system may be so effected by it that our memories and mindset may be altered as a result. This can be seen with post traumatic stress symptoms, discussed in Bourtchouldaze. She writes that traumatic memories so alter the way our memory records that they are extremely visual and they force other memories to be not recorded, such as route daily events (pg 101). The idea that someone’s memory can not only be amplified for a specific period of time, but that they way they remember is actually altered (made more visual) is really interesting to me. But even after reading about this phenomenon in both Schacter and Bourtchouldaze, I still wonder why exactly this occurs.

Furthermore, with regards to Kandel’s discussion of habituation, I started wondering if it is possible to be fully habituation to something that may otherwise cause symptoms of post traumatic stress. If someone expects a bad situation- if what would normally be classified as a traumatic event is part of someone’s world of expectations- then wouldn’t it seem that they shouldn’t exhibit post traumatic stress memory alterations? If a dog can become habituated to a car-horn over a period of time, can people be habituated to war or murder or something equally shocking? People seem to make the argument in the affirmative when they talk about desensitization and video games and America’s youth of today. But what about with actual events in people’s lives?

4 comments:

geoffrey said...

i also find the idea of habituation very interesting. You brought up the example of the dog and a car horn, in my mind i thought of a very real example of a failure of habituation. As i understand it, horses tend to be very restless on highly windy days, and it is dangerous to ride them. This is because every time the wind gusts and moves around foliage nearby them, horses get scared that the rustling is some kind of predator in the bushes. In terms of PTSD and this phenomenon, it seems to me that PTSD does not turn into habituation exactly because that is part of how PTSD affects people. So someone with PTSD who was attacked by someone hiding in the bushes would probably always react like the horse, and never habituate to rustling leaves even if they knew it was a windy day. In terms of war and murder, i am not exactly sure what your asking, but if you mean could a soldier who would normally be expected to dislike or be appalled by war become habituated, i would argue yes and no. As far as i know, those people who have significant trouble with war do not do very well with it ever, though i could see that it ceases to surprise them after they had been in enough life threatening situations, or seen enough gore. Also, you said: "can people be habituated to war or murder or something equally shocking". The problem i see here is, who thinks war and murder are shocking? Certainly not everyone, and certainly what is murder to one person, could easily be called justice by another. However, this difference is not necessarily that one person is habituated and one person is not, it def has much to do with the culture from which they perceive the situation.

Cory Antiel said...

I love this habituation research.

Catie wrote about habituation saving us from a life of constant discomfort, but habituation also affects our reaction to pleasurable (or at least sexual) stimuli—as Kandel's stimulating paragraph on sexual habituation in rats on page 168 shows. So habituation saves us at least from a life of constant over-stimulation.

Geoffry's example of someone with PTSD from being attacked by someone hiding in a bush is not only an illustration of failed habituation, but also of successful sensitization. On page 201, Kandel describes how habituation gives rise to weaker synaptic potential and sensitization gives rise to stronger synaptic potential. This attack victim's PTSD looks a lot like a sort of long term sensitization to rustling bushes. It makes sense then that your neurons would be transformed enough by an extremely traumatic experience to lead to post-traumatic stress.

The comments on murder-habituation got me thinking about a more kind of social habituation. This is a far cry from war and murder, but Geoffry's thought on how culture affects ones perceptions led me to this: I have become completely habituated to my mother yelling at me to clean my room. It happened several hundred times in high school, and somewhere after the 60th time, it started going in one ear and out the other. I think this goes one small step beyond Pavlov's dogs and their reactions to stimuli (and a giant leap beyond a single neuron's action potential), but the same sort of habituation is at work here for this social desire/command.

Stephanie A said...

This isn't totally related, but I read a fascinating article in the Washington Post over break. It described a clinical trial that is using ecstasy to treat people with severe PTSD. Something about how the drug works in the brain allows the patients to talk about their traumatic experience without feeling as afraid or anxious as they normally would. What was so interesting was how quickly the drug worked on the PTSD and how lasting the affect of it was. After taking the drugs during two consecutive therapy sessions, a majority of the patients saw their PTSD symptoms drastically reduced for up to a year. It seems like the drug doesn't work on the memory systems specifically. The drug allows the patients to talk about and process the event while they're "high" but after the drug has worn off, remembering the event is less frightening. There's a lot of skepticism out there about using party drugs to treat patients, but it seemed to work for a lot of people.

Unknown said...

Habituation is definitely an interesting concept. I really liked everyone's examples of how it occurs. To an extent I agree with both Catie and Geoffrey about their thoughts about habituation and war/murder. To a certain degree people are affected by cultural thought on these subjects but at the same time I feel that it is a type of habituation. The first time a child watches a news report about a murder or war story, they are left distraught and a little shocked that these things happen, but as time goes on, and they see more news reports of the same nature, the more habituation takes place. They no longer become shocked. However, this would only occur in a culture that regularly shows these types of news reports.

I also agree with Cory's comment about social habituation. There are certain sounds in the home that you stop responding to, such as a parent shouting for you to clean or to wake up. The sound of a shouting voice can therefore begin to elicit a certain response, very much like Pavlov's dogs. I hear my mother shout from the other room, don't actually hear the words, but respond yeah.
Explicitly trained stimuli (paired associations that would not be typically paired, the word for which has conveniently blanked from my mind) seem equally interesting. Ringing the dinner bell and your mouth waters. It is very interesting that 2 non-related items can be linked through repeated pairing. It reminds me very much of Adolf Huxley's A
Brave New World, in which people are given trained responses through subliminal night messages. Very obviously these are blatantly different situations, and yet there is a parallel. any two items innately opposite could be paired and illicit a reaction. Once one is taken away for a given period of time the reaction would remain given the stimulus. This also reminds me of the situation with the amnesic patient who was pricked by the needle. Her association of the memory remained even though she did not remember the initial event. the prick was associated with the doctor.