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Biochemistry of Learning

The Aplysia mollusk is helping researchers learn more about how we learn. Image courtesy of Flickr user Max0rz.

All of us have developed ways to learn new things—reading, discussing, attending cultural events, perusing the web, participating in conferences and meetings, and so on. In fact, the whole point of education is not to stuff us with facts and figures, but to prepare us for a lifetime of informal learning once we leave the formality of school.

Like most things, learning lends itself to scientific analysis. It is well established, for example, that multiple learning experiences spread over time are more effective than single events or multiple episodes massed together. Alas, most college students realize this too late as they cram for final exams.

A new study by a group of neuroscientists at the University of Texas asks whether the timing and spacing of multiple learning experiences matters for enhancing learning. The test subject isn’t human, but the mollusk Aplysia, which enjoys a well characterized experimental protocol to study how the snails become skilled at withdrawal from unpleasant electrical shocks. When these beasts are learning to avoid the shocks, two biochemical pathways are activated: protein kinase A (PKA) and extracellular signal–regulated kinase (ERK). The two pathways are both needed to potentiate long term learning but they occur at different rates, suggesting that the sequencing of the multiple shocks might influence the behavioral learning response.

Taking this hypothesis as a starting point, rather than the standard series of five shocks spread evenly at 20 minute intervals, the Texas scientists gave various irregularly spaced doses of the electrical shock. The result was that while both the standard and the optimal new protocol produced learning that lasted one day, only the non-uniform learning procedure persisted through five days of retention.

It probably shouldn’t be too much of a surprise that learning and memory are determined by cascades of biochemical interactions. If there is a lesson for humans to be derived from experiments on the lowly Aplysia, it would be that careless assumptions about how learning best occurs may be wrong. And happily, there is always a new way to learn about learning.

Tom Tritton is the president of CHF.

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