The memory for time and space differentially engages the proximal and distal parts of the hippocampal subfields CA1 and CA3

Abstract

A well-accepted model of episodic memory involves the processing of spatial and non-spatial information by segregated pathways and their association within the hippocampus. However, these pathways project to distinct proximodistal levels of the hippocampus. Moreover, spatial and non-spatial subnetworks segregated along this axis have been recently described using memory tasks with either a spatial or a non-spatial salient dimension. Here, we tested whether the concept of segregated subnetworks and the traditional model are reconcilable by studying whether activity within CA1 and CA3 remains segregated when both dimensions are salient, as is the case for episodes. Simultaneously, we investigated whether temporal or spatial information bound to objects recruits similar subnetworks as items or locations per se, respectively. To do so, we studied the correlations between brain activity and spatial and/or temporal discrimination ratios in proximal and distal CA1 and CA3 by detecting Arc RNA in mice. We report a robust proximodistal segregation in CA1 for temporal information processing and in both CA1 and CA3 for spatial information processing. Our results suggest that the traditional model of episodic memory and the concept of segregated networks are reconcilable, to a large extent and put forward distal CA1 as a possible “home” location for time cells.

Enhanced LTP of population spikes in the dentate gyrus of mice haploinsufficient for neurobeachin

“…This suggests that potentiation of the population spike, and not the EPSP, forms the physiological basis for delayed spatial learning. Furthermore, while both CA1 and the dentate gyrus are important sites for spatial learning 41,42 , the dentate gyrus is also important for the discrimination of similar environments (pattern separation) 43 . In line with this, an increase in LTP has been shown to coincide with less specific hippocampal place fields 44 .…”

Biological Sex and Sex Hormone Impacts on Deficits in Episodic-Like Memory in a Rat Model of Early, Pre-motor Stages of Parkinson's Disease

“…Data from rodent studies further underscore the need to evaluate and compare androgen impacts on lateral and medial entorhinal cortices and on CA1 and CA3 hippocampal subfields. Like gonadal hormones, these loci have been shown to play striking, domain-specific roles in what, where, and where elements of episodic memory [e.g., (128,(163)(164)(165)(166)(167)(168)(169)]. Finally, there are intriguing data showing pivotal roles for hippocampal area CA3 (89) and for functional interactions between medial prefrontal cortex and the CA1 and CA3 subfields (170)(171)(172) in the integration of "What, " "Where, " and/or "When" information into cohesive episodic memories.…”

Methylmercury Interactions With Gut Microbiota and Potential Modulation of Neurogenic Niches in the Brain

“…The hippocampus is critical for memory and learning. These processes rely on complex and intricate neuronal circuitry, involving dentate gyrus granular, CA3 and CA1 pyramidal cell synapses (excitatory trisynaptic neuronal circuit) (Beer et al, 2018). The former neurons are continued renewed at the hippocampal subgranular zone (SGZ) neurogenic niche, which harbors neural stem cells (NSC).…”