Biology subjects

Jacob, P.-Y.

Publications and source records attributed to Jacob, P.-Y..

4 recordsLinked to original sources

bioRxiv2025

Neuronal recordings in head-fixed and freely-moving mole-rats

Mole-rats are subterranean rodents that have evolved remarkable sensory adaptations to life in underground tunnel systems, yet their neural mechanisms remain largely unexplored. Here, we present a protocol for in vivo electrophysiological recordings in awake, head-fixed, and freely moving African mole-rats (Fukomys anselli/micklemi), overcoming unique challenges of studying the neurobiology of subterranean species. For example, we find that mole-rat brain physiology impacts survival after surgeries, with higher carbon dioxide concentrations required for recovery compared to other rodents, likely due to a mutation in the chloride-potassium symporter KCC2. Having addressed the challenges, we used tetrodes and Neuropixels probes to record single-unit activity and local field potentials (LFP) across several cortical and subcortical regions for several weeks. We observed single units responsive to auditory and visual stimuli in the superior colliculus, and hippocampal recordings in freely moving mole-rats revealed prominent theta rhythms at frequencies lower than those observed in any other rodent species to date. Finally, we performed integrated three-dimensional and two-dimensional probe-track analysis within the same brain using tissue clearing, light sheet imaging, rehydration, and vibratome sectioning, and we present a newly developed stereotaxic brain atlas for implantation and histological alignment. The established methodology will guide future studies in comparative rodent neurobiology, providing further insights into neurobiological adaptations to subterranean environments. Given their phylogenetic and ecological similarities, we expect our protocols to be transferable to other subterranean species, including the widely studied naked mole-rat (Heterocephalus glaber). HighlightsO_LIProtocols for chronic and acute electrode implantations in mole-rats C_LIO_LIStereotaxic brain atlas for the Ansells mole-rat (https://doi.org/10.17617/3.UNDKRO) C_LIO_LINeuropixels and tetrode single-unit recordings in head-fixed and freely moving mole-rats C_LIO_LIIntegrated 3D (tissue clearing) and 2D (histology) probe-track analysis within the same brain C_LIO_LIDiscovery of low-frequency hippocampal theta rhythm in Ansells mole-rats C_LI

neuroscience↗

bioRxiv2025

Dynamics of thalamic directional coding under vestibular imbalance

Head direction cells (HDCs) encode the animals orientation in space and form a core component of the brains navigation system. While their dependence on vestibular input is well established, how directional circuits respond to unilateral vestibular loss (UVL) -- the most frequent and ecologically relevant form of vestibular imbalance -- remains largely unknown. UVL offers a powerful model to investigate how spatial circuits adapt to asymmetric sensory disruption and partial deafferentation. To explore this, we examined the impact of UVL on anterior thalamic nuclei (ATN) activity and spatially tuned neurons in freely moving rats following unilateral vestibular neurectomy (UVN). UVN induced long-lasting alterations in ATN firing dynamics, including reduced theta modulation, diminished burst firing, and selective disruption across functionally defined neuronal classes: head-direction and speed-modulated cells were strongly affected, while angular head velocity and position cells remained largely preserved. Despite initial degradation, HDCs persisted and progressively regained directional tuning. Crucially, spike waveform analysis revealed two distinct HDC subtypes with markedly different vulnerabilities: one subtype showed reduced prevalence and degraded tuning, whereas the other remained resilient and supported the recovery of directional coding. These findings uncover a previously unrecognized heterogeneity within the head direction system and show that compensation following UVL is partial, cell type-specific, and functionally selective. Together, they offer new insight into sensory plasticity within thalamic navigation circuits and provide a framework to understand spatial deficits associated with vestibular imbalance.

neuroscience↗

bioRxiv2024

Retrosplenial cortex encodes both local and global space in connected environments

In everyday life, mammals navigate through environments composed of multiple interconnected spaces. Understanding how the brain encodes space in such complex settings is essential to uncover the mechanisms that support flexible navigation in the real world. In this study, we investigated how the retrosplenial cortex (RSC) and the hippocampus (HPC) encode spatial information in multi-room environments by recording neuronal activity in rats exploring environments composed of two or four connected rooms. These environments varied both in their structural layout and in their sensory features, allowing us to disentangle the influence of environmental geometry from that of local sensory cues. We found that two types of directional coding coexist within the RSC: classical head direction cells maintained a stable preferred firing direction across all rooms, while multidirectional cells expressed room-specific directional tuning that followed the geometric structure of the environment (e.g., 180{degrees} or 90{degrees} rotations). In addition, non-directional RSC neurons displayed room-specific spatial firing patterns that repeated across rooms following geometric transformations, similar to the activity observed in multidirectional cells. In contrast, hippocampal place cells either remapped between rooms or showed simple translational repetition, without preserving any geometric alignment. Taken together, these findings reveal a functional dissociation between retrosplenial and hippocampal spatial codes. The RSC supports a structured, multi-scale representation of space, segmenting the environment into locally anchored reference frames embedded within a coherent global geometry. The HPC, by contrast, encodes room-specific representations independently for each compartment. This division may support flexible navigation in complex environments by integrating geometry-based spatial segmentation and unification in the RSC with context-specific encoding in the HPC, thereby enabling multi-level spatial coding across interconnected spaces.

neuroscience↗

bioRxiv2018

A spatial code in the dorsal lateral geniculate nucleus.

Since their discovery in the early 70s1, hippocampal place cells have been studied in numerous animal and human spatial memory paradigms2-4. These pyramidal cells, along with other spatially tuned types of neurons (e.g. grid cells, head direction cells), are thought to provide the mammalian brain a unique spatial signature characterizing a specific environment, and thereby a memory trace of the subjects place5. While grid and head direction cells are found in various brain regions, only few hippocampal-related structures showing place cell-like neurons have been identified6,7, thus reinforcing the central role of the hippocampus in spatial memory. Concurrently, it is increasingly suggested that visual areas play an important role in spatial cognition as recent studies showed a clear spatial selectivity of visual cortical (V1) neurons in freely moving rodents8-10. We therefore thought to investigate, in the rat, such spatial correlates in a thalamic structure located one synapse upstream of V1, the dorsal Lateral Geniculate Nucleus (dLGN), and discovered that a substantial proportion (ca. 30%) of neurons exhibits spatio-selective activity. We found that dLGN place cells maintain their spatial selectivity in the absence of visual inputs, presumably relying on odor and locomotor inputs. We also found that dLGN place cells maintain their place selectivity across sessions in a familiar environment and that contextual modifications yield separated representations. Our results show that dLGN place cells are likely to participate in spatial cognition processes, creating as early as the thalamic stage a comprehensive representation of one given environment.

neuroscience↗