Biology subjects

Chadney, O. M. T.

Publications and source records attributed to Chadney, O. M. T..

3 recordsLinked to original sources

bioRxiv2026

The emergence of a novel CA1 spatial map requires direct entorhinal input

The hippocampus and its main input, the entorhinal cortex, are essential for memory formation, yet how they interact to do so remains unresolved. Hippocampal CA1 pyramidal neurons exhibit spatial receptive fields which reorganize unpredictably upon exposure to a novel environment, a process called remapping, considered a model of memory formation. CA1 neurons integrate both hippocampal and direct entorhinal inputs, but their relative contributions to spatial coding are unclear. Here we combined population recordings of CA1 neurons with optogenetic silencing of their direct entorhinal input. While this manipulation did not impact spatial firing in a familiar environment, it impaired remapping in a novel environment, resulting in the emergence of a stable hybrid map combining features of both environments. This shows the direct entorhinal pathway plays a specific role in CA1 novelty detection, enabling the plasticity necessary to drive the reorganisation of spatial firing patterns, preventing interference between memories in different contexts.

neuroscience↗

bioRxiv2026

Heterogeneous single-cell dynamics support stable population codes for objects in the mouse anterior cingulate cortex

Remembering object locations is crucial for survival, yet how the anterior cingulate cortex (ACC) encodes spatial features across repeated experiences has not been fully characterized. Using longitudinal calcium imaging in freely moving mice, we tracked excitatory ACC neurons while animals explored objects across multiple days. We demonstrate that the ACC employs a highly dynamic coding strategy: while the overall proportion of object-responsive neurons remains constant across sessions, the specific identities of these cells fluctuate, showing a continuous turnover alongside a small, stable core. This dynamic coding is modulated by behavior, with high-exploring mice exhibiting greater cellular stability. Crucially, population-level analyses reveal that stable spatial representations emerge from collective dynamics rather than fixed single-cell identities. Population decoding demonstrates that information becomes linearly separable and highly efficient at a coarser ensemble scale. Thus, the ACC achieves representational stability through emergent network organization despite persistent single-cell dynamics.

neuroscience↗

bioRxiv2023

Direct Entorhinal Control of CA1 Temporal Coding

During behavior, hippocampal neurons fire in consistent theta sequences, organized by the theta rhythm, which have been linked to predictive coding of future actions. The mechanisms of sequence generation are yet unclear, but in the hippocampal CA1 subfield, are thought to involve both major input streams into CA1 neurons, from CA3 pyramidal neurons and directly from entorhinal cortex. We disentangled the role of these two afferent input with highly specific optogenetic inhibition limited to the direct entorhinal afferents of CA1, thereby leaving the rest of the hippocampal-entorhinal circuit intact. While CA1 spatial firing properties were largely unaffected, theta phase precession was largely abolished. Surprisingly, while theta phase precession is thought to generate theta sequences, theta sequences were actually strengthened when it was suppressed. These results suggest that sequence generation is internal to the hippocampus, while the entorhinal inputs may act as a supervisory signal driving learning and representational updates.

neuroscience↗