"Dry Cleaning Effect" Explained by Forgetful Yale Researcher

It happens all the time. You're getting ready to go to work and you remind yourself that you need to stop off on the way to drop off the dry cleaning. You remind yourself when you're putting on your shoes. You remind yourself when you get in the car. But then, all of a sudden, you're at work with a pile of dirty clothes still in your back seat. What happened?

Researchers at Yale describe in an article appearing in today's issue of PNAS how dueling brain systems clash to thwart non-routine efforts, from running an errand before work to substance abuse and even to obsessive compulsive behaviors.

From the press release:

"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.'"

Their experiments in mice consisted of disrupting these brain structures and having the mice complete a landmark navigation and spatial learning tasks. The mice with impaired striatum suffered on the former, but did much better on the latter, while the inverse was true in mice with impaired hippocampuses.

This finding has import for understanding mental illnesses where patients show destructive, habit-like patterns of behavior or thought, such as with obsessive compulsive disorder, Tourette's and drug addiction. All of these illnesses involve abnormal function of the striatum, which, in light of these findings, could also involve disruption of the interaction between these two learning systems, leading to habits that become 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."

The article will appear in the forthcoming issue of PNAS.