Biology subjects

Lagache, T.

Publications and source records attributed to Lagache, T..

3 recordsLinked to original sources

bioRxiv2018

Tracking Activity In A Deformable Nervous System With Motion Correction And Point-Set Registration

The combination of fluorescent probes with time-lapse microscopy allows for the visualization of the entire neuronal activity of small animals, such as worms or cnidarians, over a long period of time. However, large deformations of the animal combined with the natural intermittency of neuronal activity make robust automated tracking of firing fluorescent neurons challenging. Here we present an hybrid approach where (i) a subset of very bright neurons is used as moving reference points (fiducials) to estimate the elastic deformation of the animal; (ii) deformation is frame-by-frame corrected, and firing neurons are aligned at each time with the initial mask; and (iii) point-set registration is used to robustly track the intermittent activity of all the immobilized neurons. We compare different registration strategies with manual tracking performed over {approx}620 neurons over 100 time frames in the cnidarian Hydra vulgaris.\n\nIndex TermsFluorescence imaging, wavelet detection, tracking, point-set registration, elastic deformation, Thin Plate Spline (TPS) transform, Coherent Point Drift (CPD), Hydra.

neuroscience↗

bioRxiv2018

Live Mouse Tracker: real-time behavioral analysis of groups of mice

Preclinical studies of psychiatric disorders require the use of animal models to investigate the impact of environmental factors or genetic mutations on complex traits such as decision-making and social interactions. Here, we present a real-time method for behavior analysis of mice housed in groups that couples computer vision, machine learning and Triggered-RFID identification to track and monitor animals over several days in enriched environments. The system extracts a thorough list of individual and collective behavioral traits and provides a unique phenotypic profile for each animal. On mouse models, we study the impact of mutations of genes Shank2 and Shank3 involved in autism. Characterization and integration of data from behavioral profiles of mutated female mice reveals distinctive activity levels and involvement in complex social configuration.

animal behavior and cognition↗

bioRxiv2018

Electrodiffusion model of synaptic potentials in dendritic spines

When modeling electric current flow in neurons and excitable cells, traditional cable theory ignores electrodiffusion (i.e. the interaction between electric fields and ionic diffusion) as it assumes that concentration changes associated with ionic currents are negligible. This assumption, while true for large neuronal compartments, fails when applied to femto-liter size compartments such as dendritic spines - small protrusions that form the main site of synaptic inputs in the brain. Here, we use the Poisson (P) and Nernst-Planck (NP) equations, which relate electric field to charge and couple Ficks law of diffusion to the electric field, to model ion concentration dynamics in dendritic spines. We use experimentally measured voltage transients from spines with nanoelectrodes to explore these dynamics with realistic parameters. We find that (i) passive diffusion and electrodiffusion jointly affect the kinetics of spine excitatory post-synaptic potentials (EPSPs); (ii) spine geometry plays a key role in shaping EPSPs; and, (iii) the spine-neck resistance dynamically decreases during EPSPs, leading to short-term synaptic facilitation. Our formulation can be easily adopted to model ionic biophysics in a variety of nanoscale bio-compartments.

biophysics↗