Working and Reference Memory Tasks Trigger Opposed Long-Term Synaptic Changes in the Rat Dentate Gyrus


  • Missaire Mégane
  • Fraize Nicolas
  • Comte Jean-Christophe
  • Truchet Bruno
  • Parmentier Régis
  • Salin Paul-Antoine
  • Malleret Gaël


  • Dentate gyrus radial maze reference memory synaptic plasticity working memory
  • Dentate gyrus radial maze reference memory synaptic plasticity working memory

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Long-term storage of information into memory is supposed to rely on long-term synaptic plasticity processes. The detection of such synaptic changes after training in long-term/reference memory (RM) tasks has yet been scarce, variable and only studied on a short time scale. Short-term or working memory (WM) is largely known to depend on persistent neuronal activity or short-term plasticity. However, processing information into WM could also involve long-term synaptic changes that could be responsible for the erasure/forgetting of items previously stored in WM and acting as proactive interference. In order to study long-term synaptic changes associated with RM or WM, we trained chronically implanted rats in 3 different radial maze tasks: a classical RM task and 2 WM tasks involving different levels of proactive interference. Synaptic responses in the dentate gyrus were recorded during 2 × 24 h in freely moving rats after training. We found that consolidation of long-term information leads first to a delayed synaptic potentiation, occurring 9 h after RM training that is replaced by a synaptic depression once the RM rule is fully acquired. In contrast, optimal information processing into WM triggers a synaptic depression immediately after training and lasting 3 h that could act as a mechanism for interference erasure/forgetting.

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