Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 114, Issue 46, Pages E9972-E9979Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1714248114
Keywords
memory; engram; hippocampus; episodic; amnesia
Categories
Funding
- RIKEN Brain Science Institute
- Howard Hughes Medical Institute
- JPB Foundation
Ask authors/readers for more resources
Recent studies identified neuronal ensembles and circuits that hold specific memory information (memory engrams). Memory engrams are retained under protein synthesis inhibition-induced retrograde amnesia. These engram cells can be activated by optogenetic stimulation for full-fledged recall, but not by stimulation using natural recall cues (thus, amnesia). We call this state of engrams silent engrams and the cells bearing them silent engram cells. The retention of memory information under amnesia suggests that the time-limited protein synthesis following learning is dispensable for memory storage, but may be necessary for effective memory retrieval processes. Here, we show that the full-fledged optogenetic recall persists at least 8 d after learning under protein synthesis inhibition-induced amnesia. This long-term retention of memory information correlates with equally persistent retention of functional engram cell-to-engram cell connectivity. Furthermore, inactivation of the connectivity of engram cell ensembles with its downstream counterparts, but not upstream ones, prevents optogenetic memory recall. Consistent with the previously reported lack of retention of augmented synaptic strength and reduced spine density in silent engram cells, optogenetic memory recall under amnesia is stimulation strength-dependent, with low-power stimulation eliciting only partial recall. Finally, the silent engram cells can be converted to active engram cells by overexpression of alpha-p-21-activated kinase 1, which increases spine density in engram cells. These results indicate that memory information is retained in a form of silent engram under protein synthesis inhibition-induced retrograde amnesia and support the hypothesis that memory is stored as the specific connectivity between engram cells.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available