Learning and memory: Remembrance of things similar...(nature)

By Rachel Jones -

What did you have for breakfast today? And what did you watch on TV last night? These questions are deceptively difficult, because they require your brain to distinguish between many almost identical memories (of other breakfasts and other evenings) and to identify the right one. This process is known as 'pattern separation'. A new study uses an elegant technique to clarify how the dentate gyrus contributes to pattern separation by activating distinct populations of granule cells in response to similar events.

Deng et al. used 'TetTag' transgenic mice to identify neurons that were activated by different experiences. Such mice are treated with doxycycline to inhibit the expression of a doxycycline-sensitive transgene; when doxycycline treatment is withdrawn, activation of a neuron will cause it to permanently express the tau-lacZ marker. The mice can then be placed back on doxycycline treatment and exposed to a specific experience before their brains are removed and examined; neurons that are activated by the latter experience can also be identified by looking for the expression of immediate-early genes. This allows researchers to compare the activation of neurons at two defined time points in the same animals.

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