Recoding a cocaine-place memory engram to a neutral engram in the hippocampus.

Trouche S
Perestenko PV
van de Ven GM
Bratley CT
McNamara CG
Campo-Urriza N
Black SL
Reijmers LG
Dupret D

Here, Trouche and colleagues report that silencing hippocampal nerve cells active in a given environment allowed for the activation of a subset of quiet nerve cells, then enabling the emergence of an alternative information code for space. When this intervention was applied in an environment where mice had received cocaine, it cancelled an otherwise long-lasting drug-place preference.

Scientific Abstract

The hippocampus provides the brain's memory system with a subset of neurons holding a map-like representation of each environment experienced. We found in mice that optogenetic silencing those neurons active in an environment unmasked a subset of quiet neurons, enabling the emergence of an alternative map. When applied in a cocaine-paired environment, this intervention neutralized an otherwise long-lasting drug-place preference, showing that recoding a spatial memory engram can alleviate associated maladaptive behavior.

Example spatial rate maps of simultaneously-recorded neurons (one neuron per row) from the dorsal hippocampus of a c-fos::ArchT mouse exploring a circular environment. The optogenetic silencing of (ArchT-tagged) neurons actively representing that environment allows for the emergence of an alternative place code by previously quiet hippocampal neurons.
Example spatial rate maps of simultaneously-recorded neurons (one neuron per row) from the dorsal hippocampus of a c-fos::ArchT mouse exploring a circular environment. The optogenetic silencing of (ArchT-tagged) neurons actively representing that environment allows for the emergence of an alternative place code by previously quiet hippocampal neurons.
Citation

2016.Nat. Neurosci., 19(4):564-7.