Biology subjects

Long, J.-L.

Publications and source records attributed to Long, J.-L..

3 recordsLinked to original sources

bioRxiv2026

Gradual evolution of multiplexed spatial coding within a conserved hippocampal scaffold

The hippocampus constructs spatial maps for navigation, yet their format differs markedly across species. Whether divergences reflect ecological adaptation, phylogenetic architecture, or flexible coding strategy within a conserved circuit has been difficult to disentangle. We recorded CA1 in rats and tree shrews (Tupaia belangeri chinensis), a mammal phylogenetically and ecologically between rodents and primates, using identical tasks and analyses. Unlike the position-dominant code of rats, tree shrew CA1 exhibited a hybrid representation: weaker position selectivity, stronger non-positional tuning, and prevalent multiplexing approaching primate characteristics. Multiplexed populations decoded location as accurately as rat position populations while using fewer neurons, suggesting computational advantages of high-dimensional coding. Despite this representational shift, proximo-distal gradient, pattern completion, and global remapping persisted. Representational format can be tuned without altering the underlying circuit. Tree shrews occupy an evolutionary intermediate in which ancestral network dynamics are repurposed for efficient multiplexed coding, tracing a transition toward primate-like spatial representations.

neuroscience↗

bioRxiv2025

Dentate gyrus drives pattern separation in proximal CA3 during rate, but not global, remapping

The dentate gyrus (DG) transforms overlapping experiences into discrete memory traces, yet how DG output shapes population coding within the hippocampus remains unclear. We combined selective DG lesions with large-scale recordings across the CA3 proximo-distal axis as rats explored environments varying in contextual similarity. Global remapping in CA3 remained robust following DG lesion, whereas rate-based contextual coding was substantially attenuated, most strongly in proximal CA3 and attenuating distally, paralleling mossy-fiber topography. Granule cells and mossy cells additionally coded complementary aspects of local objects and mediated CA3 responses to object manipulation. These data causally link the enhanced rate coding of proximal CA3 to its preferential DG innervation and support a dual organization of contextual discrimination: categorical changes in environmental identity are signaled independently of the DG, whereas fine-grained discrimination is facilitated by DG-mediated rate modulation. By selectively amplifying rate-coded discrimination of subtle contextual differences, the DG sharpens the hippocampal network's capacity to resolve overlapping experiences into distinct representations.

neuroscience↗

bioRxiv2024

Ternary representation of contextual information along the CA1 transverse axis

Episodic memory refers to the recollection of personally experienced events anchored in spatial contexts. Salient objects within a navigation environment serve as both landmarks and event cues; however, the nuanced integration of these elements during episodic memory formation is not well understood. The mnemonic functions of the hippocampal CA1 region are partially organized along its transverse axis, with proximal and distal subregions preferentially processing spatial and non-spatial information, respectively. Based on comprehensive analysis of neuronal responses along the CA1 proximodistal axis to manipulations of environmental cues and object features, we identified an event-like population coding within CA1 following object displacement. In addition, the neuronal responses at both initial and relocated object locations were shaped by distinct convergent inputs. These findings highlight the specific roles that objects may play in spatial navigation and memory encoding, providing novel insights into the selective processing of object-related information within the entorhinal-hippocampal network. Significance StatementSalient objects within a navigation environment serve as both landmarks and event cues critical for episodic memory. However, the enigmatic contribution of objects to the "where" and "what" components of episodic memory remains poorly understood. Here we comprehensively analyzed the neuronal responses in the hippocampal CA1 region along its transverse axis, to manipulations of environmental cues and object features. Our results revealed an event-like population coding within CA1 following object displacement, suggesting a minimal landmark role these objects play during memory formation. This study provides novel insights into the selective and flexible processing of object-related information within the entorhinal-hippocampal network.

neuroscience↗