Examining Action Potential Waveform Diversity in Neuronal Populations of Midbrain Organoid Models

Over the last decade, pre-clinical research has witnessed the advancement of human induced pluripotent stem-cell derived 3D brain organoid models and their differentiation into specific brain regions. In the realm of Parkinsons disease research, development of midbrain-specific organoids has enabled studies of this neurodegenerative disorder in patient derived 3D organoid models that attempt to recapitulate the human brain complexity. Within this line of research, neural functionality of the organoid models is established through electrophysiology. As a novel methodological approach, this study aimed to establish whether clustering of electrophysiological activity originating from midbrain organoids would aid in identifying different types of action-potential waveforms exhibited by neurons within the organoid model. Long-term extracellular electrophysiological recordings were conducted by use of a multi-electrode array device. The local field potential signal was spike-sorted, and the extracted putative neuron units were clustered into groups of spike waveform profiles. After establishing this methodological analysis pipeline, the clusters of waveform types were further analyzed in terms of electrophysiology. Results revealed that the clustering approach was successful at identifying three types of spike waveforms categories. Furthermore, it was proposed that one spike waveform profile potentially originated from dopaminergic neurons, which were one on the neural cells populating the organoid models. Overall, this study has successfully established a new methodological clustering approach to analyze electrophysiological data recoded from 3D organoid models in the context of Parkinsons disease modelling and organoid model development research.