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Golbabaei, A.

Publications and source records attributed to Golbabaei, A..

2 recordsLinked to original sources
bioRxiv2025

Neurogenesis-dependent transformation of hippocampal memory traces during systems consolidation

Memories for events (i.e., episodic memories) change qualitatively with time. Systems consolidation theories posit that organizational changes accompany qualitative shifts in memory resolution, but differ as to the locus of this reorganization. Whereas some theories favor inter-regional changes in organization (e.g., hippocampus[->]cortex; multiple trace theory), others favor intra-regional reorganization (e.g., within-hippocampus; trace transformation theory). Using an engram tagging and manipulation approach in mice, here we provide evidence that intra-regional changes in organization underlie shifts in memory resolution. We establish that contextual fear memories lose resolution as a function of time, with mice exhibiting conditioned freezing in both the training apparatus (context A) and a second apparatus (context B) at more remote delays (freezingA {equiv} freezingB at remote delay). By tagging either hippocampal (dentate gyrus) or cortical (prelimbic cortex) neuronal ensembles in context A, and then pairing their optogenetic activation with shock (in context C), we monitored the resolution of these artificially-generated memories at recent versus remote post-conditioning delays by testing mice in contexts A and B. Hippocampal engrams for a fear conditioning event were initially high-resolution (recent delay: freezingA >> freezingB) but lost resolution with time (remote delay: freezingA {equiv} freezingB). In contrast, cortical engrams were initially low-resolution and remained low-resolution over time (recent and remote delay: freezingA {equiv} freezingB). Transformation of hippocampal engrams was dependent on adult hippocampal neurogenesis. Eliminating hippocampal neurogenesis arrested hippocampal engrams in a recent-like, high-resolution state where mice continued to exhibit discriminative freezing at remote delays. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/658072v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@1aec109org.highwire.dtl.DTLVardef@36e20org.highwire.dtl.DTLVardef@1332e46org.highwire.dtl.DTLVardef@123215d_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗
bioRxiv2023

A shift in the mechanisms controlling hippocampal engram formation during brain maturation

The ability to form precise, episodic memories develops with age, with young children only able to form gist-like memories that lack precision. The cellular and molecular events in the developing hippocampus that underlie the emergence of precise, episodic-like memory formation are unclear. In mice, the absence of a competitive neuronal engram allocation process in the immature hippocampus precluded the formation of sparse engrams and precise memories until the fourth postnatal week, when inhibitory circuits in the hippocampus mature. This age-dependent shift in precision of episodic-like memories involved the functional maturation of parvalbumin-expressing interneurons in subfield CA1 by extracellular perineuronal nets which is necessary and sufficient for the onset of competitive neuronal allocation, sparse engram formation, and memory precision. One-Sentence SummaryEpisodic-like memory precision requires maturation of hippocampal inhibitory interneurons by the extracellular matrix.

neuroscience↗