Take note, students: Mice that 'cram' for exams remember less

Mice

It's been more than 100 years since German psychologist Hermann Ebbinghaus determined that learning interspersed with rest created longer-lasting memories than cramming, or learning without rest.

Yet it's only much more recently that scientists have begun to understand the underlying molecular mechanisms for this phenomenon. In a study published Monday in the journal PNAS, researchers examined the physical changes in the brain cells of mice while "training" their eyes to keep track of a moving image.

Researchers examined the horizontal optokinetic response, or HOKR, in mice to determine what rest interval was best suited to increasing their memory.

HOKR is what makes it possible for a rider in a train to visually track the moving scenery. While the process is unconscious, it involves frequent, minute eye movements.

Mice were fastened to a device that immobilized their heads and then were made to look at a revolving, checkered image that triggered the eye response. A was used to determine when the tracking began and when it stopped.

While the eyes of are initially unable to track the revolving image at a high speed, they eventually adapt to faster and faster movement. This tracking ability is retained for a period of time before it is forgotten.

Some of the mice were allowed to rest between training sessions, while others were not. Researchers noted clear differences between the mice that were given rest time "spacing" and those that received no breaks, or "massed training."

"One hour of spacing produced the highest memory retention at 24 hours, which lasted for one month," wrote lead study author Wajeeha Aziz, a molecular physiologist at the National Institute for Physiological Sciences in Okazaki, Japan, and her colleagues.

"Surprisingly, massed training also produced long-term memory. ... However, this occurred slowly over days, and the memory lasted for only one week."

Credit: PNAS, 10.1073/pnas.1303317110

Researchers compared brain tissue from the two groups of trained mice and with those of mice that received no training. They found that both groups of trained had reduced synapses in a specific type of nerve cell, Purkinje neurons.

However, spacing the appeared to make these structural changes in synapses occur more quickly, the authors said.

"Further investigations are needed to elucidate the precise molecular mechanisms that regulate the temporal features of long-lasting memory, and the structural modifications of synapses provides an indispensable readout for such studies," the authors concluded.


Explore further

A better way to remember

More information: Distinct kinetics of synaptic structural plasticity, memory formation, and memory decay in massed and spaced learning, www.pnas.org/cgi/doi/10.1073/pnas.1303317110

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Dec 24, 2013
i have always wondered why alien abductees never reported "learning sessions." it would seem to me that they might want to know things like that. i mean if they are smart enough to travel the stars it seems odd that they would merely cut you up and then drop you off. if i were an alien i would get one snockered and then see how well it managed an unachievable task.

Dec 24, 2013
'Cramming' is not intended to form long term memories, only to refresh existing memory or establish perishable memory that will last only until the exam is sat.

The exam system suits some students so well that they can achieve almost perfect scores and then have little working knowledge of the subject they have just aced after only a few weeks or even days.

The equivalent in athletic terms is the short term build up of fast twitch muscles for a sprint when long distance running is the goal of educators. A sprint test takes less than 30 seconds, a long distance run takes an hour (120 times longer) so only the sprint is tested.

Refreshing existing memory is quite different. This is like re indexing existing information for quick access. The article considers only the establishment of new memories.

Dec 27, 2013
My experience, at least on some subjects, was that the more you "study" the worse you will do on the test.

The best formula for me often didn't even involve taking notes, but it depends on the class. Just pay attention in class, review the material a time or two, and if you haven't learned it by then you probably won't. Maybe one last glance at your notes or whatever you were having trouble with right before the test, but this whole thing of spending an hour or two going over notes right before a test, no it won't work. You aren't "understanding" the material, you're just trying to memorize a bunch a facts, most of which won't be on the test anyway.

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