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In Frontiers in bioengineering and biotechnology

Detection, characterization and classification of patterns within time series from electrophysiological signals have been a challenge for neuroscientists due to their complexity and variability. Here, we aimed to use graph theory to characterize and classify waveforms within biological signals using maxcliques as a feature for a deep learning method. We implemented a compact and easy to visualize algorithm and interface in Python. This software uses time series as input. We applied the maxclique graph operator in order to obtain further graph parameters. We extracted features of the time series by processing all graph parameters through K-means, one of the simplest unsupervised machine learning algorithms. As proof of principle, we analyzed integrated electrical activity of XII nerve to identify waveforms. Our results show that the use of maxcliques allows identification of two distinct types of waveforms that match expert classification. We propose that our method can be a useful tool to characterize and classify other electrophysiological signals in a short time and objectively. Reducing the classification time improves efficiency for further analysis in order to compare between treatments or conditions, e.g., pharmacological trials, injuries, or neurodegenerative diseases.

Rodriguez-Torres Erika Elizabeth, Paredes-Hernandez Ulises, Vazquez-Mendoza Enrique, Tetlalmatzi-Montiel Margarita, Morgado-Valle Consuelo, Beltran-Parrazal Luis, Villarroel-Flores Rafael

2020

XII nerve, deep learning, electrophysiological signals, graph theory, maxcliques, pre-Bötzinger complex, sigh, visibility graphs