Some coma patients who appear to be completely unresponsive to the outside world are still capable of the most basic kind of learning, according to a small new study. Researchers found that both vegetative and “minimally conscious” patients were capable of a Pavlovian response, learning to associate a noise with a slightly unpleasant stimulus.
The researchers built on the work of 19th-century Russian psychologist Ivan Pavlov, who famously conditioned his dogs to salivate at the ring of a bell by associating the sound with the presentation of food. In this case, they sounded a tone, which was followed about 500 milliseconds later with a light puff of air to the eye [Scientific American]. At first the patients only responded after the puff of air by blinking or twitching or flinching. But after repeated trials, 15 of the 22 patients began to blink or flinch immediately after the tone sounded, before the puff of air. Electrodes by their eyes picked up the subtle muscle movements.
A control experiment doing the same tests on people under general anaesthesia did not produce the same responses, suggesting that the learning does not happen when truly unconscious [BBC News]. The study also suggests that even patients in persistent vegetative states may have some very rudimentary level of consciousness that isn’t detected in other tests.
The fascinating (but preliminary) findings, presented in Nature Neuroscience, may eventually help doctors evaluate coma patients’ potential for recovery. The authors found a strong correlation between cognitively damaged patients who seemed to exhibit such learning and those who showed some level of improvement months after their injury, as measured by a standard coma recovery scale [The Scientist]. Because the experimental setup is so simple, doctors who don’t have access to sophisticated brain imaging techniques could use this system to inform their diagnoses.
These study also suggests possible new forms of therapy to lead researcher Tristan Bekinschtein. Next his team hopes to explore whether learning this type of task might actually help recovery. “If you train networks in the brain, you can transform the network itself,” he says [New Scientist].
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Image: flickr / el7bara
September 22nd, 2009 at 12:40 am
I believe this is only the tip of what you will discover through this avenue of research. In 1963 I was stationed in northern Africa and was bitten by a mosquito. I came down with fevers three times a day for two weeks, on the last fever before being given the malaria medication at that time, my fever hit 106.8 degrees. How did I know this when I was lying in a hospital bed in Spain unable to move, not even to open my eyes or move my fingers. But, I could hear everything in the ward. I heard the nurses and orderlies walking around and talking, especially the orderly that came to my bed and took my temperature, and immediately called for the nurses and doctors. They, the nurses, orderlies and doctors, immediately started treating me for the 106.8 fever. They stripped the bed and me, placed an inflatable mattress under me and started cold water running through it, a metal large bowl was placed on the bed table at the end of the bed, alcohol (I could smell it) was pored into the bowl followed by pieces of ice pored into the bowl. They dipped towels into the bowl, wrung them out slightly and placed them over my body, I could smell the alcohol but could not feel the cold from the iced alcohol bath. I still was unable to move even to open my eyes, but my hearing was such that I could hear a pin drop in the open ward. I believe I was in a coma at that time due to the fever. The malaria medication was administered to me. After a period of time the fever broke, I slept and then woke up. I have never had a re-occurence of the fever, but what happened that day I have never forgotten. That was 46 years ago.
September 22nd, 2009 at 10:48 am
Dean- Wow. That is truly fascinating! I find very interesting that you were able to hear and smell, but not feel the cold of the ice. That really has to say something about how the coma affects the brain and the body. I wonder if that is something typical of coma patients…
I’ve always thought that there was more consciousness to coma than we give it credit for. I think this is a very under explored avenue of research and I hope this will lead to more involved studies in this field.
September 22nd, 2009 at 1:43 pm
Hi Tom – I am not sure about the “typical coma patients”, I have never worked in the medical field, but I do believe it needs more study. I can still see the images in my mind that occurred during that fever.
September 22nd, 2009 at 4:39 pm
“Dean” is the same churchy poser poster as last weeks respondents to news of a HPV vaccine.
Rather than state their religious based views on a scientific web site, they create B.S. testimonials to sow doubt to the casual observer. If you look at the timing of these testimonial posts you see they are often the same hypocrite masquerading as several people.
This article obviously poses thorny questions about euthanasia, and moral issues associated with decisions best left to families and their medical practitioners.
September 22nd, 2009 at 4:51 pm
Coma Coma Coma Chameleon – What are you talking about? It sounds like you have me mixed up with someone else. You should be careful about making false accusations. Or are you just trying to cause problems?
September 23rd, 2009 at 10:51 am
Dean, I am sorry if you had a coma. Who wants to make trouble with a coma guy! That would be ridiculous.
I’m also sorry for calling you churchy. That wasn’t very nice either.
And I am soo sorrry for calling your b.s. testimonial a b.s. testinonial! I mean 106.8 degrees? You’ve got to be kidding me. If you are aided by a straw to type this, I am ptobably going to hell, but come on-106.8!
September 23rd, 2009 at 4:49 pm
Coma Coma Coma Chameleon – Yes, 106.8, and if I could get my military health records I would prove it to you. I’m sorry you don’t believe me, but I still would not wish you to go to hell. I am just thankful to be living a fairly normal life (another tidbit of info you probably don’t believe), especially to reach my age. I have learned in my life time that each of us sees the other like you are, I am glad I am like I am. I do not ask you to believe, but what I have written is what has happened, end of my story, goodby.
September 30th, 2009 at 1:40 pm
Coma Coma Coma Chameleon and Dean – I believe Dean…wanna know why? My husband is currently in what the doctors call a Vegetative Coma State and just 4 days ago he had a fever that spiked in the 106′s. Thank you Dean…for giving me hope!
February 9th, 2010 at 8:07 pm
Coma Coma Coma Chameleon sounds like one of those scientifically inclined casual observers who remain attached to outdated scientific facts, and are just as dogmatic about their beliefs as those who are attached to outdated religious beliefs.
30 years ago I was part of a study group working with a physician interested in the healing effects of meditation on serious illness. One of her patients was a woman with Lupus who had been in a vegetative coma for several months a few years before. During the period of her coma she overheard the conversations going on around her, including her husband telling the attending physician to give up and unplug her life-support. In coma she resolved that if she ever recovered she would immediately divorce him. She did, and did so, and felt it was one of the two most life-enhancing decisions of her life, the other being the decision to practice daily meditation as part of her health regime.
I’m sure CCCC will question the scientific credibility of meditation as an effective healing modality, so I recommend he try it. Test it out for himself. ddo some research.