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Thursday, August 27, 2009

Naps Promote Learning of Movement Skills

Whether you are learning to play the piano or learning to throw a football to a fast-breaking receiver, the necessary muscle movements have to be memorized. Converting the memory of movements into long-lasting form takes several hours or more for the brain to "consolidate" the learned movements. This process can be interrupted by trying to learn a different movement during this vulnerable period. For example, consolidation of the memory for a few chords on the piano can be disrupted by trying to learn finger movements on a computer keyboard during this vulnerable period.

Another feature of motor learning is that delayed gains in skill performance can occur after a latent period of several hours after an effective learning experience. This delayed performance gain depends on the first post-training night's sleep (I have explained the role of sleep on other kinds of memory in my book on improving memory).

Now comes a study that shows that daytime naps condense the time course of motor memory consolidation. In the experiment, subjects learned a five-element finger-to-thumb opposition sequence with their non-dominant hand. Then the experimenters tested the effect of a post-training nap. Compared to no-nap controls, a 90-minute daytime nap immediately after training markedly reduced the susceptibility to post-training interference effects and produced a much earlier expression of delayed gains within 8 hours post training. Thus, both memory-enhancing effects were produced by the nap.

Would a shorter nap produce the same effect? We don't know. It wasn't tested. Another untested possibility is that the daytime nap might enhance the memory consolidation that is normally produced by a night's sleep after a motor learning experience, especially if the task is rehearsed that same day after the nap.


Korman, M. et al. 2009. Daytime sleep condenses the time course of motor memory consolidation. Nature Neuroscience. 10 (9): 1206-1213.

Monday, August 10, 2009

Here's Why Marijuana Impairs Memory Formation

Scientists have known for some time that marijuana impairs the ability to convert short-term or working memories into lasting form. Now they know why. The protein synthesis machinery in the hippocampus is necessary to accomplish lasting memory formation, and a study of mouse hippocampus revealed that marijuana impairs the protein synthesis pathway responsible for memory consolidation.

Puighermannal, E. et al. 2009. Cannabinoid modulation of hippocampal long-term memory is mediated by mTOR signaling. Nature Neuroscience. On-line edition, Aug. 2; doi:10.1038/nn.2369

Wednesday, August 05, 2009

Increasing Working Memory Makes Even Adults Smarter

I have pointed out a study in an earlier post a study that showed the IQ of children around age six can be increased by training them to increase their working memory capacity. This ability of working memory training to improve intelligence has now been demonstrated in young adults (mean age = 25.6 years). Subjects were trained on a so-called dual n-back test in which subjects were asked to recall a visual stimulus that they saw two, three or more stimulus presentations in the past. The task was dual in the sense that two stimuli were presented simultaneously for a half second, followed by a 2.5 second delay until the next stimulus. One stimulus type was a square in which another smaller square was shown in one of eight possible positions within the larger square. At the same time one of eight consonants were presented through headphones. A response was required every time one of the presented stimuli matched the one that had been presented n positions back in the sequence. As performance improved with each block of trials, the task demands were increased my shifting from two-back to three, then three to four, etc. Daily training took about 25 minutes.

Intelligence tests were periodically given that were based on visual analogy problems of increasing difficulty. Each problem presented a matrix of patterns in which one pattern was missing. The task was to select the missing pattern among a set of given response alternatives. This kind of testing measures what is called "fluid" intelligence, which refers to the ability to reason and solve new problems independently of previously acquired knowledge. What the investigators found was that working memory training improved scores on the intelligence test. Moreover, the effect was dose-dependent, in that intelligence scores increased in a steady straight-line fashion as the number of training sessions increased from 8 to 12 to 17 to 19. Working memory capacity presumably transfers to visual analogy tasks because you have to hold many visual features in working memory while you try to identify which pattern is missing in the matrix.

These results also challenge a widely held view that intelligence becomes fixed at a young age and cannot be increased by experience.

Source: Jaeggi, S. M. et al. 2008. Improving fluid intelligence with training on working memory. Proc. Natl. Acad. Science.