Spouse #1: I had to take the trash out because you forgot again.
Spouse #2: I know. I didn’t sleep well last night.
Spouse #1 (hefting an iron skillet): Well, you’re going to get some good “sleep” right now.
It’s been known for a long time that sleep plays an important role in memory and learning. But, most of that time, scientists got their ideas about the role of sleep by seeing how people messed up when they weren’t getting any. Freud was one of the first to put a formal argument on the table. He claimed that experiences of the day were “rehearsed” during sleep and that ideas “came together,” much like a performance comes together after a lot of practice. But, given Siggy’s overall batting average, most experts tended to eventually dismiss his proposition.
Now, Science Daily (September 16, 2009) reports that Freud might actually have had a hit on his hands. [Editor's note: Be sure not to miss that the allusion to a "hit" here reflects a deft feathering together of the "performance" metaphor and the "batting average" metaphor, each used above.] Research at the Center for Molecular and Behavioral Neuroscience (Rutgers University) and at the College de France (Paris) has identified a specific process by which memory consolidation (a form of learning) occurs. The researchers found that during deep sleep, the hippocampus* experiences intense, compressed oscillations that they named “sharp wave ripples.” Now you might be thinking, “Well, how do they know that these sharp wave ripples have anything to with memory consolidation?” Good question. This is what they did. They trained some rats in a fairly complex navigation task and allowed the rats to sleep after each session. Some of the rats got to have their sharp wave ripples and others were prevented from having them by a mild form of electrical stimulation. And get this: The rats that didn’t get their ripples couldn’t remember how to do the task.
So far, so good. However, the lead researcher from Rutgers, Gyorgy Buzsaki, got a bit full of himself and claimed that, “This is the first example that if a well-defined pattern of activity in the brain is reliably and selectively eliminated, it results in memory deficit.” Well, he couldn’t slide that one past The Brain & Behavior Blogger.
The B&B Blogger knows that Dr. Todd Sacktor, an eminent neuroscientist at SUNY Medical Center in Brooklyn, had demonstrated some years ago that networks of neurons that repeatedly fire together put themselves on a sort of cognitive speed-dial (using a brain secretion called PKMzeta to grease the circuit). Sacktor argues that when we recall something from our past, each of the neurons in that network contributes a piece of a particular memory. However, the coolest part of Sacktor’s research is that he was able to create a chemical compound (he calls “ZIP”) that, when injected directly into the brains of rats, breaks the speedy connections among neurons and effectively wipes out the associated memory. Others scientists now have such “Mind Sweeper” compounds under development as well.
What the B&B Blogger would like to know is whether ZIP would cause Sacktor’s rats to miss their ripples. Then, we’d really be on to something.
* This is a part of your brain, not a college for large, thick-skinned, plant-eating animals in Africa.
Original references for any studies, books or articles cited by the Brain and Behavior Blogger can be obtained by contact with his very dear friend, Dr. Rob Snyder (r.snyder@tier1performance.com), an organizational psychologist with a severe neuroscience-research reading habit.
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[...] Sleep, Learning and Memory [...]
Gyorgy Buzsaki, got a bit full of himself and claimed that, “This is the first example that if a well-defined pattern of activity in the brain is reliably and selectively eliminated, it results in memory deficit.” Well, he couldn’t slide that one past The Brain & Behavior Blogger.
The statement is absolutely true. Nobody has ever selectively eliminated a well-defined brain pattern before. A brain pattern means that a constellation of neurons fire together and give rise a mesoscopic activity that can be recorded as a ‘mean field”. Todd Sacktor’s findings with PKCzeta are fantastic but he did eliminate a brain pattern. The enzyme may be activated by sharp wave-ripples or other patterns and the drug his group used to interfere with plasticity is downstream from population neuronal patterns. Thus, it is not not known that the blocker would affect ripples but even if it does, I would be surprised if the effect would be selective to this particular brain pattern. Hope you can see the difference between electrical patterns and molecular events.