Monday, October 20, 2008

The "Dry Cleaning Effect" in Mice

In the ridiculous extrapolation of the day, we have a paper that purports to solve the problem of why we forget to drop off our dry cleaning...based on results from a study conducted in mice. I don't know about you, but I don't remember ever seeing a mouse drop off his clothes at the dry cleaner. And as an added bonus, the authors may have cured substance abuse and OCD!

Here's the press release from Yale:
'Dry cleaning effect' explained by forgetful Yale researcher

Yale researchers have described how dueling brain systems may explain why you forget to drop off the dry cleaning and may point to ways that substance abusers and people with obsessive compulsive disorder can overcome bad habits.

In Proceedings of the National Academy of Sciences, Christopher J. Pittenger, M.D., and colleagues describe a sort of competition between areas of the brain involved in learning that results in what Pittenger calls the "dry cleaning effect."

Unfortunately (and in their pertetually annoying fashion), PNAS has not yet made the article available to us non-press plebians, so we'll have to rely on EurekAlert! for now.

One area of the brain called the striatum helps record cues or landmarks that lead to a familiar destination. It is the area of the commuter's brain that goes on autopilot and allows people to get to work, often with little memory of the trip.

But when driving to an unfamiliar place, the brain recruits a second area called the hippocampus, which is involved in a more flexible system called spatial learning. The commuter must employ this system if he or she wants to run an errand before work.

"When you have driven the same route many times and are doing it on autopilot, it can be really difficult to change," said Pittenger, assistant professor of psychiatry at Yale and senior author the paper. "This is why I cannot, for the life of me, remember to drop off my dry cleaning on the way to work. If I'm not paying enough attention right at that moment, if I am thinking about something else, I just sail right on by."

Call me humanocentric, but I think distractibility (and the frontal lobes) might have a role in this sort of absentmindedness. Nevertheless, the study itself could be perfectly reasonable, and the results sound interesting:

Pittenger and Yale colleagues Anni S. Lee and Ronald S. Duman developed a way to study how these two modes of learning might be interconnected in mice.

In one group, they disrupted areas of the striatum in mice and discovered that their ability to complete landmark navigation tasks was impaired. However, these mice actually improved on tasks that involved spatial learning.

Conversely, when the researchers disrupted an area of the hippocampus involved in spatial learning, the animals could no longer navigate spatially but learned landmark tasks more quickly.

But then we see the concluding extrapolation, and it involves mice in cognitive-behavioral therapy:

Pittenger speculates that the interactions between these two systems may be important for understanding certain mental illnesses in which patients have destructive, habit-like patterns of behavior or thought. Obsessive-compulsive disorder, Tourette syndrome, and drug addiction involve abnormal function of the striatum and may also involve disruption of the interactions between the two learning systems, which may make habits stronger and less flexible.

"This is part of what we are doing in cognitive-behavioral therapy when we teach patients to recognize their destructive habits, to take a step back, and to learn to do things differently," Pittenger said. "What we're really asking them to do is to use one of these systems to overcome and, ultimately, to re-train the other."

I understand the plight of basic researchers these days, how essential it is emphasize the clinical relevance of one's work in order to obtain NIH funding, but sometimes it can be a bit of a stretch...

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At October 20, 2008 11:51 PM, Anonymous Anonymous said...

Hmm, actually, I gather from the press release (which you always have to hype to compete with the gazillion other press-releases out there), that the researchers may have found something which is actually quite known from other (or the same? You're right, the paper isn't even out, yet!) paradigms: habit learning is suppressed by other learning mechanisms. I can even find that in flies (just re-submitted my revised version to JNeurosci). What I thought was surprising was that apparently the habit learning striatum also inhibited spatial learning, which is something I have never heard about. One could explain that by assuming that they overtrained animals and then, of course, without habit formation, they would do better in the spatial paradigm, because no habit would interfere with new learning.
So in principle it all makes sense and the reference to the dry cleaner is actually quite accurate: the test in rats is to make them sick for the food they press the lever for in an operant chamber. If they have formed a habit, they nevertheless run to the lever and press it, even though the food makes them sick. The rats 'know' better and still perform the behavior just as the author knows better and still drives to work, Or the drug addict, or the OCD patient, etc.
That doesn't mean it must be all the same mechanism. But it's striking that the phenotypes are so similar and the brain structures are all the same, at least on the level we are currently able to look at it.

At October 21, 2008 1:09 AM, Blogger The Neurocritic said...

My perspective might be skewed by the [human] cognitive neuroscience literature, but I do agree that flies and mice and humans share some of the same learning mechanisms. Relying on the press release for details is a bit silly, so we don't really know yet what learning paradigms were used. My biggest problem was with the way the issue was framed. Remembering to drop off the dry cleaning doesn't really involve new spatial learning, because presumably you've been there before. It's a matter of remembering to interrupt your usual commute habit, or overriding prepotent response tendencies, in frontal lobe-speak.

Bjoern said:
...habit learning is suppressed by other learning mechanisms. I can even find that in flies (just re-submitted my revised version to JNeurosci). What I thought was surprising was that apparently the habit learning striatum also inhibited spatial learning, which is something I have never heard about.

First, I look forward to reading your JNeurosci paper (where other learning mechanisms inhibit habit learning, even in flies). Second, as for habit learning inhibiting other types of learning, here's a neuroimaging article demonstrating that priming (a form of "habit learning" or implicit memory) can inhibit subsequent explicit memory (for a list of words). However, this type of priming was associated with prefrontal cortex, rather than the striatum.

Wagner AD, Maril A, Schacter DL.
Interactions between forms of memory: when priming hinders new episodic learning. J Cogn Neurosci. 2000;12 Suppl 2:52-60.

At October 22, 2008 7:41 PM, Anonymous Anonymous said...

It never ceases to amaze me how researchers will often set about investigating an area with minimal consideration of clinical relevance.

I await news of their next research findings that highlight other elements I can file away as interesting but not extremely useful when compared to more impacting studies.


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