Biology subjects

Gardella, C.

Publications and source records attributed to Gardella, C..

3 recordsLinked to original sources

bioRxiv2017

Blindfold learning of an accurate neural metric

The brain has no direct access to physical stimuli, but only to the spiking activity evoked in sensory organs. It is unclear how the brain can structure its representation of the world based on differences between those noisy, correlated responses alone. Here we show how to build a distance map of responses from the structure of the population activity of retinal ganglion cells, allowing for the accurate discrimination of distinct visual stimuli from the retinal response. We introduce the Temporal Restricted Boltzmann Machine to learn the spatiotemporal structure of the population activity, and use this model to define a distance between spike trains. We show that this metric outperforms existing neural distances at discriminating pairs of stimuli that are barely distinguishable. The proposed method provides a generic and biologically plausible way to learn to associate similar stimuli based on their spiking responses, without any other knowledge of these stimuli.

neuroscience↗

bioRxiv2017

Identifying Parameters Of Host Cell Vulnerability During Salmonella Infection By Quantitative Image Analysis And Modeling

Salmonella target and enter epithelial cells at permissive entry sites: some cells are more likely to be infected than others. However the parameters that lead to host cell heterogeneity are not known. Here, we quantitatively characterized host cell \"vulnerability\" towards Salmonella infection based on imaged parameters. We performed successive infections of the same host cell population followed by automated high-throuput microscopy and observed that infected cells have higher probability of being re-infected. Establishing a predictive model we identified two combined origins of host cell vulnerability: the pathogen-induced cellular vulnerability emerging from Salmonella uptake and persisting at later stage of the infection, and the host cell-inherent vulnerability. We linked the host cell inherent vulnerability with its morphological attributes such as the local cell crowding, and with host cell cholesterol content. This showed that the probability of Salmonella infection success can be forecast from morphological or molecular host cell parameters.

microbiology↗

bioRxiv2016

Closed-loop estimation of retinal network sensitivity reveals signature of efficient coding

According to the theory of efficient coding, sensory systems are adapted to represent natural scenes with high fidelity and at minimal metabolic cost. Testing this hypothesis for sensory structures performing non-linear computations on high dimensional stimuli is still an open challenge. Here we develop a method to characterize the sensitivity of the retinal network to perturbations of a stimulus. Using closed-loop experiments, we explore selectively the space of possible perturbations around a given stimulus. We then show that the response of the retinal population to these small perturbations can be described by a local linear model. Using this model, we computed the sensitivity of the neural response to arbitrary temporal perturbations of the stimulus, and found a peak in the sensitivity as a function of the frequency of the perturbations. Based on a minimal theory of sensory processing, we argue that this peak is set to maximize information transmission. Our approach is relevant to testing the efficient coding hypothesis locally in any context where no reliable encoding model is known.

neuroscience↗