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Hardy, S. V.

Publications and source records attributed to Hardy, S. V..

3 recordsLinked to original sources

Transformation of Petri net models of biological signaling networks into influence graphs

A common depiction for biological signaling networks is the influence graph in which the activation and inhibition effects between molecular species are shown with vertices and arcs connecting them. Another formalism for reaction-based models is the Petri nets which has a graphical representation and a mathematical notation that enables structural analysis and quantitative simulation. In this paper, we present an algorithm based on Petri nets topological features for the transformation of the computational model of a biological signaling network into an annotated influence graph. We also show the transformation of the Petri nets model of the beta-adrenergic receptor activating the PKA-MAPK signaling network into its representation as an influence graph.

bioinformatics↗

NeuroTorch: A Python library for neuroscience-oriented machine learning

Machine learning (ML) has become a powerful tool for data analysis, leading to significant advances in neuroscience research. While ML algorithms are proficient in general-purpose tasks, their highly technical nature often hinders their compatibility with the observed biological principles and constraints in the brain, thereby limiting their suitability for neuroscience applications. In this work, we introduce NeuroTorch, a comprehensive ML pipeline specifically designed to assist neuroscientists in leveraging ML techniques using biologically inspired neural network models. NeuroTorch enables the training of recurrent neural networks equipped with either spiking or firing-rate dynamics, incorporating additional biological constraints such as Dales law and synaptic excitatory-inhibitory balance. The pipeline offers various learning methods, including backpropagation through time and eligibility trace forward propagation, aiming to allow neuroscientists to effectively employ ML approaches. To evaluate the performance of NeuroTorch, we conducted experiments on well-established public datasets for classification tasks, namely MNIST, Fashion-MNIST, and Heidelberg. Notably, NeuroTorch achieved accuracies that replicated the results obtained using the Norse and SpyTorch packages. Additionally, we tested NeuroTorch on real neuronal activity data obtained through volumetric calcium imaging in larval zebrafish. On training sets representing 9.3 minutes of activity under darkflash stimuli from 522 neurons, the mean proportion of variance explained for the spiking and firing-rate neural network models, subject to Dales law, exceeded 0.97 and 0.96, respectively. Our analysis of networks trained on these datasets indicates that both Dales law and spiking dynamics have a beneficial impact on the resilience of network models when subjected to connection ablations. NeuroTorch provides an accessible and well-performing tool for neuroscientists, granting them access to state-of-the-art ML models used in the field without requiring in-depth expertise in computer science.

neuroscience↗

Distinct forms of structural plasticity of adult-born interneuron spines induced by different odor learning paradigms

During development and in adulthood the morpho-functional properties of neural networks constantly adapt in response to environmental stimuli and learned experiences. One of the processes that allows neuronal networks to be constantly reshaped is synaptic plasticity, which is induced in response to sensory experience and learning. Synaptic plasticity allows for the formation/elimination of synaptic connections as well as the strengthening of pre-existing ones. The olfactory system is particularly prone to constant morpho-functional reshaping of neural networks and synaptic rewiring throughout the lifespan of an animal, mainly because of the presence of continuous neurogenesis in the olfactory bulb (OB). This constant synaptic rewiring brought by adult-born neurons is modulated by the level of odor-induced activity and olfactory learning. It remains, however, unclear whether the complexity of distinct odor-induced learning paradigms and sensory stimulation induces different forms of structural plasticity. In the present study, we developed an analytical pipeline to perform 3D reconstructions of spines from confocal images followed by clustering of reconstructed spines based on different morphometric features and in relationship with different sensory stimuli and learning paradigms. We show that while sensory deprivation decreased the overall density of adult-born neurons in the OB without any noticeable changes in the morphometric properties of these spines, simple and complex odor learning paradigms triggered distinct forms of structural plasticity. A simple odor learning task affected the morphometric properties of the spines without any changes in spine density, whereas a complex odor learning task induced changes in spine density, without substantial changes in the morphology of the spines. Our work reveals the vast panoply of distinct forms of synaptic plasticity of adult-born neurons in the OB tailored to the complexity of odor-learning paradigms and sensory inputs.

neuroscience↗