😊

Thanks, Taro!

These time-dependent shifts in sub-engram engagement indicate that systems consolidation involves reorganization _within_ (as well as across) brain regions.

We provide evidence for projection-defined 'sub-engrams' that contribute differentially to memory expression at recent and remote delays.

This adds to an emerging picture that not only do new neurons influence encoding of new memories but they _shape_ and _remodel_ existing memories. These shifts in resolution may facilitate generalization of event based memories beyond the original situation.

Within hippocampal shifts in memory resolution depended on ongoing hippocampal neurogenesis. Blocking neurogenesis prevents time-dependent shifts in memory resolution, preserving hippocampal engrams in high fidelity ‘recent memory’-like states.

We found hippocampal engrams were initially high resolution but lost resolution with time. In contrast, cortical engrams were low res and stayed low res over the course of systems consolidation

In this paper we tracked the resolution of hippocampal and cortical components of an event memory (modifying a false memory paradigm first developed by @okaysteve.bsky.social). This allowed us to adjudicate between the different theoretical accounts of systems consolidation…

Some favor inter-regional changes (e.g., hippocampus to cortex [multiple trace]) whereas other favor intra-regional changes (e.g., within hippocampus [trace transformation])

Memories for events (i.e., episodic memories) tend to lose precision with time and models of systems consolidation propose that organizational changes accompany these shifts in memory resolution… but theories differ as to the locus of this reorganization…

Appreciate giving me 10!

In summary, we established whole-genome, multimodal single-cell history tracing, applicable to a wide range of experimental systems.
Our lab is now applying HisTrac to study id specification and plasticity (e.g., memory) and we look forward to sharing exciting results soon!

Yeah it feels like only about 25% of it is open right now. Gonna be great when it’s all done

Gotta get there early. Was only 1 or 2 of us early doors.

Role and influence, yes. But, the biological mechanisms? Maybe not in a functional/systems/computational model...

Mind you, though I am not objective here, I basically buy @franklandlab.bsky.social's account of infantile amnesia as being driven by neurogenesis:

www.science.org/doi/full/10....