Engram cells retain memory under retrograde amnesia

By T. Ryan, Dheeraj S. Roy, Michele Pignatelli, Autumn L Arons, Susumu Tonegawa. 2015

639 citations recorded by the source corpus.

Experimental recovery from retrograde amnesia When memory researchers induce amnesia, they normally assume that the manipulations prevent the memory engram from effective encoding at consolidation. In accordance with this, Ryan et al. found that after the injection of protein synthesis inhibitors, animals could not retrieve a memory. However, to their surprise, the memory could nevertheless be reactivated by light-induced activation of the neurons tagged during conditioning. Increased synaptic strength that is the result of cellular consolidation is thus not a critical requisite for storing a memory. Science, this issue p. 1007 Memory can be retrieved by optogenetic activation of the neurons involved in memory formation when memories would not normally have been stored. Memory consolidation is the process by which a newly formed and unstable memory transforms into a stable long-term memory. It is unknown whether the process of memory consolidation occurs exclusively through the stabilization of memory engrams. By using learning-dependent cell labeling, we identified an increase of synaptic strength and dendritic spine density specifically in consolidated memory engram cells. Although these properties are lacking in engram cells under protein synthesis inhibitor–induced amnesia, direct optogenetic activation of these cells results in memory retrieval, and this correlates with retained engram cell–specific connectivity. We propose that a specific pattern of connectivity of engram cells may be crucial for memory information storage and that strengthened synapses in these cells critically contribute to the memory retrieval process.

Subfields: Cellular and Molecular Neuroscience, Cognitive Neuroscience

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Cellular and Molecular Neuroscience

1. S. Tonegawa
2. Jacob A. Berry
3. R. Redondo
4. Ronald L. Davis
5. Anna Phan
6. Xu Liu
7. S. Ramirez
8. Yi Zhong

In Cognitive Neuroscience

1. S. Tonegawa
2. R. Redondo
3. Xu Liu
4. S. Ramirez
5. Jacob A. Berry
6. Ronald L. Davis
7. Y. Dudai
8. Paul W. Frankland

Citations in the corpus

• Dopamine Neurons Mediate Learning and Forgetting through Bidirectional Modulation of a Memory Trace (2018, background): “Recent studies in the mouse have indicated that forgetting of long-term fear memories after protein synthesis inhibition (Ryan et al., 2015) or during Alzheimer’s disease (Roy et al., 2016) occurs through disruption of retrieval and not erasure of the engram.”
• Memory Engram Cells Have Come of Age. (2015, positive): “Recently, one study investigated structural plasticity in the DG engram cells holding an engram component for the contextual information of the CFC experience (Ryan et al., 2015).”