Neurodegenerative diseases such as Parkinsons’s or Alzheimer’s diseases are characterized by the aggregation of misfolded proteins in insoluble inclusions. These inclusions trigger cellular dysfnctions and are therefore thought to play an important role in the development of these pathologies. They appear following a conserved pattern in subgroups of patients. In Parkinson’s disease, the small presynaptic protein alpha-synuclein (aSyn) is the main component of protein deposits termed Lewy bodies and Lewy neurites. These appear following a stereotypical pattern known as “Braak staging” in a consequent subset of patients. The pattern of inclusion formation partly follows neuroanatomical connectivity, suggesting that protein aggregation propagates in neural networks. Prion diseases such as kuru or Creutzfeldt-Jakob’s disease have revealed an original mechanism for propagating protein misfolding. The PrP protein, aggregated in these diseases, is able to have two radically distinct conformations. The pathological one aggregates in supramolecular assemblies, while the functional one does not. Through an incompletely understood mechanism which might share similarities with the formation of amyloid fibrils, the pathological form of the protein is able to convert the functional form into the pathological one, recruiting it into aggregates. The abnormal form of the protein is thus able to self-propagate, from cell to cell and from organism to organism. Numerous biochemical and molecular characteristics of aggregates detected in neurodegenerative diseases are shared with the prion aggregates. It is thus hypothesized that protein aggregation in neurodegenerative diseases unfolds in a similar manner to prion aggregation. In this scenario, protein aggregation is able to be transmitted from neuron to neuron following neuroanatomical connectivity, and thus propagates in a stereotypical manner in neural networks following axonal tracts. This scenario is named “prion-like hypothesis”. However, how the prion-like propagation of aSyn generates the conserved pattern of aggregates in the brain of patients is still unknown. The aim of my PhD thesis has been to decipher parameters impacting the prion-like propagation of aSyn in heterogeneous neural networks with in vitro models. I first assessed if specific neuronal populations cultured from various regions of the mouse brain exhibited the same vulnerability to the prion-like recruitment of aSyn in pathological aggregates following their exposure to exogenous aSyn fibrils. I was able to demonstrate that cortical, striatal and hippocampal primary neuronal cultures had a significant difference in their vulnerability to prion-like seeding of aSyn aggregation. I also demonstrated that this vulnerability was due to the differential expression of aSyn in these populations. I then developed a culture system allowing for the controlled reconstruction of primary murine neurons networks. This system allows for the perfect filtration of axonal outgrowth in one direction, thus allowing the reconstruction of fully oriented binary networks. Axonal growth orientation is a prerequisite to the in vitro study of pathogens propagation in neural networks. This system is the first to achieve this level of axonal filtration while allowing synaptic connectivity between the two compartments. I finally modeled aSyn prion-like propagation in these reconstructed networks by selectively introducing exogenous fluorescent aSyn fibrils in the “presynaptic” compartment and following aggregation propagation to the “postsynaptic” compartment. This propagation can only occur through crossing axons, as the two compartments are fluidically isolated. I demonstrated that anterograde aSyn prion-like propagation was relatively inefficient in this experimental framework. Indeed, while a small quantity of exogenous fibrils are transferred to postsynaptic neurons, they are not able to seed endogenous aSyn aggregation in those. [...]