Biology subjects

Brandon, M.

Publications and source records attributed to Brandon, M..

4 recordsLinked to original sources

bioRxiv2026

Medial septum glutamatergic neurons support speed coding and grid cell spatial stability in the medial entorhinal cortex

Successful navigation requires the integration of self-motion signals with spatial representations, yet the circuits that provide velocity information necessary for stable grid cell firing remain incompletely understood. Here, we identify medial septal (MS) glutamatergic neurons as a critical component of this pathway. Using cell-type-specific optogenetic silencing combined with in vivo electrophysiology in freely moving mice, we show that MS glutamatergic neurons support the fidelity of firing rate-based speed coding in the medial entorhinal cortex (MEC). Silencing this population reduced grid cell spatial periodicity and stability and produced distortions of grid firing fields. Silencing also reduced theta phase-locking strength in strongly theta-modulated MEC neurons. Model simulations of a hybrid oscillatory interference-continuous attractor network with reductions in speed-signal fidelity disrupted grid periodicity and reproduced features of the spatial distortions observed in vivo. Together, these findings identify a septo-entorhinal circuit that coordinates self-motion information with the spatial and temporal organization of MEC activity to maintain a stable neural representation of space.

neuroscience↗

bioRxiv2024

Social valence dictates sex differences in identity recognition

Social valence is the directional emotional significance affiliated with social experiences. Maladaptive processing of negative social valence (NSV) has been linked to mood disorder susceptibility, which is more prevalent in women. To determine whether there are sex differences in NSV processing, we developed social valence tasks where the identity recognition of conspecifics with distinct valences served as the readout. Male mice demonstrated identity recognition regardless of social valence. Conversely, female mice did not show identity recognition following the NSV task. In vivo calcium imaging of the dorsal CA1 further revealed sex differences in NSV processing with reduced hippocampal representation of social information in female mice. These results suggest the imprecise encoding of NSV may contribute to the heightened vulnerability to social stress-related mood disorders in women.

neuroscience↗

bioRxiv2022

Spatial memory consolidation during REM sleep requires stabilization of newly formed place cells.

The involvement of rapid-eye-movement sleep (REMs) in spatial memory formation was recently demonstrated, although how neural activity during REMs influences newly-formed place field stability remains unclear. Here, we combined large-scale single-unit recordings of mouse hippocampal CA1 with an established optogenetic approach enabling REMs-selective inhibition of medial septum GABAergic neurons (MSGABA), resulting in spatial memory deficits when applied post-learning. Although individual neural activity was unaffected by REMs-selective MSGABA inhibition during a post-learning rest session, both the synchrony of population-level activity bursts observed during REMs occurring in the rest session and place field stability measured during subsequent memory recall testing were reduced vs controls. However, the latter effect was limited to place cells participating in population activity during REMs, as stability of non-participant place cells was relatively weak and indifferent between groups. This suggests that synchronous CA1 population activity during REMs stabilizes spatial representations in a plastic subpopulation of participating CA1 neurons.

neuroscience↗

bioRxiv2019

A zero-inflated gamma model for post-deconvolved calcium imaging traces

Calcium imaging is a critical tool for measuring the activity of large neural populations. Much effort has been devoted to developing \"pre-processing\" tools applied to calcium video data, addressing the important issues of e.g., motion correction, denoising, compression, demixing, and deconvolution. However, computational modeling of deconvolved calcium signals (i.e., the estimated activity extracted by a pre-processing pipeline) is just as critical for interpreting calcium measurements. Surprisingly, these issues have to date received significantly less attention. To fill this gap, we examine the statistical properties of the deconvolved activity estimates, and propose several density models for these random signals. These models include a zero-inflated gamma (ZIG) model, which characterizes the calcium responses as a mixture of a gamma distribution and a point mass which serves to model zero responses. We apply the resulting models to neural encoding and decoding problems. We find that the ZIG model out-performs simpler models (e.g., Poisson or Bernoulli models) in the context of both simulated and real neural data, and can therefore play a useful role in bridging calcium imaging analysis methods with tools for analyzing activity in large neural populations.

neuroscience↗