When we learn associations between items or ideas, such as the value of currency used in a foreign country, the connections between certain brain cells become stronger. In the cellular process thought to underlie learning and memory—long-term potentiation (LTP)—the simultaneous activation of two connected neurons causes one cell to respond more robustly to signals from the other one. “Neurons that fire together wire together” is a phrase commonly used to describe this phenomenon.
Recent studies suggest that neuronal communication and LTP are influenced by star-shaped glial cells called astrocytes, which are known to provide nutrients to neurons and support their basic functions. However, because much of this evidence was collected from brain slices and different research groups have produced conflicting results, scientists have questioned the involvement of astrocytes in learning.
This week in PLoS Biology, neuroscientist Alfonso Araque of the Cajal Institute in Madrid, Spain, and his collaborators report novel evidence of LTP regulation by astrocytes in living rats and propose a new cellular mechanism of learning and memory. Because this study suggests that astrocytes play an integral role in storing information in the brain, it resolves an important and high-profile debate in the field.
In the study, Araque and his team focused on pairs of neurons in the hippocampus, a brain region that is crucial for learning and memory. They generated LTP either by pinching the rat’s tail or through direct electrical stimulation of the neurons.