The steady formation of new brain cells in adults may represent more than merely a patching up of aging brains, a new study has shown. The new adult brain cells may serve to give the adult brain the same kind of learning ability that young brains have while still allowing the existing, mature circuitry to maintain stability.

Hongjun Song and colleagues reported their findings in the May 24, 2007 issue of the journal Neuron, published by Cell Press.

In their experiments, they used a virus to selectively label new brain cells with a fluorescent protein in the hippocampus, a major brain center for learning and memory, of adult mice.

The researchers then analyzed the electrophysiological properties of the new neurons at different times after their formation. This analysis enabled them to measure how adaptable, or "plastic," the brain cells were.

The researchers found that the new adult neurons showed a pattern of changing plasticity very similar to that seen in brain cells in newborn animals. That is, the new adult brain cells showed a "critical period" in which they were highly plastic before they settled into the less plastic properties of mature brain cells. In newborn animals, such a critical period enables an important, early burst of wiring of new brain circuitry with experience.

Whats more, the researchers molecular analysis showed that the plasticity of new adult neurons depended on the function of one of the same types of receptors that is associated with learning-related processes in newborn animals. Such receptors are the receiving stations for chemical signals called neurotransmitters, launched from neighboring neurons to trigger a nerve impulse in the receiving neurons. Subtle alterations in receptor populations are the means by which the brain wires the preferred pathways in the process of learning and memory.

The researchers also observed in the new adult neurons anatomical evidence of the sa
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Contact: Erin Doonan
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Cell Press
23-May-2007