Contagious Itch in Humans

[thinker_jeff]

Abstract

 

Anecdotal evidence suggests “contagious” itch occurs in daily life when we see other people itch and scratch. This phenomenon has not been systematically studied previously, and factors which can amplify itch perception were unknown. We investigated whether exposure to visual cues of itch can induce or intensify itch in healthy and atopic dermatitis subjects. Participants received histamine or a saline control delivered to the forearm and were asked to watch short video clips of people scratching. Spontaneous scratching induced by visual cues was monitored and analyzed. Atopic dermatitis patients reported a higher itch intensity and scratched more frequently while watching itch videos, even in the presence of mock itch stimuli. Human susceptibility to develop itch when exposed to visual cues is confirmed and it appears amplified in atopic dermatitis sufferers. These findings suggest that interpersonal social cues can dramatically alter the subjective sensory experience of itch.

 

Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2133.2011.10318.x/abstract

 

 

 

 

[thinker_jeff]

What did they find out about itching?

The researchers monitored how 25 participants reacted when they saw a series of five-minute videos — some showing people scratching, others showing them "acting normally." The participants were divided into three groups: People suffering from eczema; healthy subjects who had an itch-inducing histamine applied to their arms; and another healthy group that was given a placebo. All three groups reacted the same way, scratching more when those on screen did, and scratching less when those on screen refrained. Notably, those doused with the itchy arm solution clawed themselves all over, not just on their arms.

 

What causes contagious itching?

Based on similar studies conducted on other primates, scientists believe this is an "inherited biological alarm" that once warned humans about potentially dangerous infections among a population. "This shows that the power of the brain is pretty extreme," says Dr. Alexandru Papoiu, one of the study's researchers. Of course, it's not the only human response that's susceptible to going viral. "The mechanisms underlying contagious itching may be similar to the ones involved in contagious yawning, a phenomenon that is still intensely studied, but not exactly clear," said Dr. Gil Yosipovitch, who led the team.

 

What's next?

Scientists now know that certain stimuli cause people to scratch even when there's no obvious reason to itch. The next step is to target the specific areas in the brain that produce those responses. "If we can understand the underlying mechanism and its cause," says Papoiu, "we should have a better chance to treat itch, targeting the central nervous system stations involved."

 

Sources: US News and World Report, Daily Mail, Telegraph

 

 

[Marat]

Yawning and laughing also spead by contagion among humans who see other humans do those things. Interestingly, I have noticed that if I yawn, it seems to induce my dogs to yawn as well. (Laughing doesn't work though.)

[thinker_jeff]

I guess that this sort of contagions were caused by "mirror neurons". Maybe someone should look into the neural system related with that.

By the way, I haven't heard of any progress on mirror neuron for a while.

Edited March 30, 2011 by thinker_jeff

[PhDwannabe]

By the way, I haven't heard of any progress on mirror neuron for a while.

 

To give you a half-informed state-of-the-science (I'm in psych, but not in the cog-neuro area): mirror neurons are a little like string theory. A good chunk of the field thinks they revolutionize our understanding of cognition and learning. Another sizable chunk think they're a fairly significant waste of time.

[thinker_jeff]

A good chunk of the field thinks they revolutionize our understanding of cognition and learning. Another sizable chunk think they're a fairly significant waste of time.

 

I agree with you that is the situation by now. I am on the positive side (the first chunk).

Just for curiousity, which side is yours?

Edited March 31, 2011 by thinker_jeff

[PhDwannabe]

I don't feel informed enough with regard to that side of the field to really register a solid opinion. I do, nonetheless, have an abiding suspicion of grand-explanatory neurological theories. It's a big mushy ball up there, and it's extremely difficult to compartmentalize it into regions and processes that make organizational sense to us. In many other fields, it's a safe bet that we'll know we were all wrong 50 years from now. In neuroscience, it's a safer bet that we'll know how dead-wrong we were 5 or 10 years from now.

[thinker_jeff]

The good thing is that you should have more chances in this field than in the classic one.

[SMF]

In a group of wild humans, hunter gatherers for example, when somebody scratches it makes great sense for the rest of the group who observe this to be vigilant for some kind of biting insect and up the criteria for what of the gazillion itchies one has that should be scratched. Because we all believe that the brain is a biological computing mechanism, and not some magic organ, there has to be a calculated representation of the connections required to link someone else’s behavior with one’s own. If we explain this linkage by a neuron, such as the mirror neuron concept, we are back to ancient and silly ideas represented by Phrenology and the “yellow Volkswagen detector” neuron. This localization of function concept (exclusive of simple sensory pathways), that PhDwannabe mentions, is one of the important philosophical concepts that neuroscience dropped in the middle of the last century. But if there isn’t an evolutionarily designed neuron for recognizing every possible image of biologically significant images, there very certainly is neural processing of these data in the brain.

 

It would require the ability to observe neural networks that might process something at the level of the itch/scratch observations in order for cognitive neuroscience to progress. I haven’t checked lately, but I think there is some progress, but what is currently ubiquitous are neurophysiological recordings of action potentials of neurons, and the signal would be detected this way, even though this neuron might have many other functions, and promote the idea of a “mirror neuron.” Most thoughtful neuroscientists are aware that this is only a placeholder for the computational concept.

 

I don’t think that neuroscience is still at such a primitive level that major upheavals will happen every 5 to 10 years. I think it will be successive refinements of current ideas, with very few completely abandoned, but it is still wide open for creating successful scientific careers. SM

 

 

[thinker_jeff]

In a group of wild humans, hunter gatherers for example, when somebody scratches it makes great sense for the rest of the group who observe this to be vigilant for some kind of biting insect and up the criteria for what of the gazillion itchies one has that should be scratched. Because we all believe that the brain is a biological computing mechanism, and not some magic organ, there has to be a calculated representation of the connections required to link someone else's behavior with one's own. If we explain this linkage by a neuron, such as the mirror neuron concept, we are back to ancient and silly ideas represented by Phrenology and the "yellow Volkswagen detector" neuron. This localization of function concept (exclusive of simple sensory pathways), that PhDwannabe mentions, is one of the important philosophical concepts that neuroscience dropped in the middle of the last century. But if there isn't an evolutionarily designed neuron for recognizing every possible image of biologically significant images, there very certainly is neural processing of these data in the brain.

 

It is OK that you are in the "second chunk" (as PhDwannable's wording); however, comparing the "mirror neuron" to the "yellow Volkswagen detector neuron" is not scientificlly correct. There are many empirical data to support the concept of mirror neuron. I'm not saying that the concept has been robust, but you have to give empirical data to abandon it.

[SMF]

Thinker_jeff, you misunderstand. I am not denying that neurophysiologists have recorded from single neurons that react to both a specific activity of the self and the same activity observed in another individual, or from a yellow Volkswagon detector neuron for that matter. The problem is with how to interpret this information. By the way, the yellow VW idea is from the title of an old philosophical neuroscience paper. The problem is with how this information is interpreted. It is impossible to have a single neuron designated specifically to identify every object or activity that might have significance to ones perceptions or actions. This raises questions, such as, what happens if one of these neurons dies, or what about when someone learns something new? The big gorilla in this room is the fact that there just aren't enough neurons available to accomplish this task in this way. What is required is an assembly of neurons that make a more generalized processor that can accomplish many more tasks than the number of individual neurons in the circuit. There will be neurons in such circuits that will, in the lab, respond to specific stimuli, but there is no way to test it completely to find out what other stimuli it might be involved in processing.

 

No one denies that we are able to recognize Volkswagons, or a mirror activity in someone else, but the brain just isn't designed around a giant library of neurons, each of which stores single concepts and objects or whatever. What the neurophysiology does is to provide data regarding the inner workings of cognitive function that can, in turn, be used for more experiments. SM

[thinker_jeff]

It is impossible to have a single neuron designated specifically to identify every object or activity that might have significance to ones perceptions or actions.

 

SM, I have never said that such concept relates to Mirror Neuron. If you think that is the concept well accepted by neuroscientists studying about mirror neuron, please give the source.

Edited April 1, 2011 by thinker_jeff

[SMF]

Thinker_jeff, you have me confused. In my first comment on this thread (#9) I commented on your original post on itchy-scratchy, and then amplified PhDwannabe’s comment regarding the error of trying to think of the brain in terms of compartmentalized regions that have the organizational sense of the output (i.e. localization of complex function). Take a look at the Wikipedia article on mirror neurons. Even though it is a decent summary it would be easy for someone seeking knowledge about this to think of a mirror neuron as a localized single processing unit with a single assigned function. I cautioned that neuroscientists don’t make this mistake, but you disagreed.

 

So, in my second post (#11) I expanded what I said further, and to this you respond in a manner that agrees with my first post. I don’t know how to respond further. I think that you are trying to put me into the controversy between cognitive groups regarding what they think is important about the mirror neuron concept. I don’t care about this. These folks are all very smart and will be able to work out their differences as more neuroscience data become available. For your, and other’s reading pleasure (I hope you like it heavy duty) here are a couple of references to articles about this issue relative to how cognitive scientists are thinking about it. SM

 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2773693/?tool=pmcentrez

 

http://jean-luc.petit.over-blog.com/article-22972759-6.html

 

 

[thinker_jeff]

Thinker_jeff, you have me confused.

 

I haven't told you what is my concept about mirror neuron so that you shouldn't think too much.

Your first artical is a serious one which we can discuss, but the second one is just a Blog which I don't care that much.

 

I don't know if you notice that the panel of "Psychiatry and Psychology" may be removed on Monday, which is a very bad news, so that we should open a new topic about mirror neuron in the panel of "Anatomy, Physiology and Neuroscience".

[SMF]

Thinker_Jeff. The second link is not a blog, it is a website where a cognitive guy is making a book chapter that he wrote available. I read about half and skimmed the rest and it appears to be a serious treatment to me. Notice that Petit cites references to support his arguments in the text and provides the full citations at the end. For me, this is the absolute minimum requirement for an online science article. In any case, I am a more mechanistic neuroscience guy and not really very interested in cognitive science, which should explain my comments so far. I would be very interested if you would research the cognitive controversy and bring a neutral summary here for discussion. That could be a lot of fun.

 

The disappearing psych section of this forum is a part of an elaborate joke that claims that SFN has been given to the Scientologists to promote their version of science. You are going to be able to trade blog comments with John Travolta and Tom Cruise! Oh boy! SM

[thinker_jeff]

SM, let me digest the first article before I open a new topic for mirror neuron. It may take a while because I can only read it in off-work time.

I still don't want to spend my time for the second one that has not been peer reviewed.

[SMF]

Thinker_jeff, I retrieved the two links from a quick search and picked them because they were full text access. There is a lot of high quality information out there. I strongly recommend, if you don't already do this, that you use Google Scholar for your searching if you want just scientific articles. SM

[thinker_jeff]

The discussion about "mirror neuron" has been continued by another topic, "Debate on Mirror Neuron", in the section of "Anatomy, Physiology and Neuroscience".

 

http://www.scienceforums.net/topic/56326-debate-on-mirror-neuron/

Edited April 11, 2011 by thinker_jeff