A geographically distributed bio-hybrid neural network with memristive plasticity

Throughout evolution the brain has mastered the art of processing real-world inputs through networks of interlinked spiking neurons. Synapses have emerged as key elements that, owing to their plasticity, are merging neuron-to-neuron signalling with memory storage and computation. Electronics has made important steps in emulating neurons through neuromorphic circuits and synapses with nanoscale memristors, yet novel applications that interlink them in heterogeneous bio-inspired and bio-hybrid architectures are just beginning to materialise. The use of memristive technologies in brain-inspired architectures for computing or for sensing spiking activity of biological neurons8 are only recent examples, however interlinking brain and electronic neurons through plasticity-driven synaptic elements has remained so far in the realm of the imagination. Here, we demonstrate a bio-hybrid neural network (bNN) where memristors work as "synaptors" between rat neural circuits and VLSI neurons. The two fundamental synaptors, from artificial-to-biological (ABsyn) and from biological-to- artificial (BAsyn), are interconnected over the Internet. The bNN extends across Europe, collapsing spatial boundaries existing in natural brain networks and laying the foundations of a new geographically distributed and evolving architecture: the Internet of Neuro-electronics (IoN).Comment: 16 pages, 10 figure

Emulating short-term synaptic dynamics with memristive devices

Neuromorphic architectures offer great promise for achieving computation capacities beyond conventional Von Neumann machines. The essential elements for achieving this vision are highly scalable synaptic mimics that do not undermine biological fidelity. Here we demonstrate that single solid-state TiO2 memristors can exhibit non-associative plasticity phenomena observed in biological synapses, supported by their metastable memory state transition properties. We show that, contrary to conventional uses of solid-state memory, the existence of rate-limiting volatility is a key feature for capturing short-term synaptic dynamics. We also show how the temporal dynamics of our prototypes can be exploited to implement spatio-temporal computation, demonstrating the memristors full potential for building biophysically realistic neural processing systems

Molecular Control of Actin Cortex Architecture During Cell Division

Animal cell shape is controlled by gradients in contractile tension of the actin cortex. The cortex is a thin actomyosin network supporting the plasma membrane. At the molecular level, contractile tension is generated by myosin motors pulling on actin filaments. Along- side myosin, actin connectivity has been shown to be key to cortical tension regulation. Understanding molecular organisation of the actin cortex is thus key to understanding cortical tension. To understand how cortical composition changes when tension changes, and to identify potential molecular regulators of cortical tension, I firstly compared protein composition of interphase and mitotic cortices. Indeed, interphase and mitotic cells were previously shown to di↵er in cortical tension. I isolated cortical fractions from cells in these stages of cell cycle, by isolating cortex-enriched blebs. Using mass spectrometry, we detected over 922 proteins in blebs isolated from synchronised cells. Among 238 actin-related proteins, we showed a role for septins in the regulation of the mitotic cell shape. Overall, we created a comprehensive dataset of potential regulators of cortex mechanics. In the second part of my PhD, I focused on the role of actin crosslinkers in cortex tension regulation. In particular, I focused on the role of actin crosslinker size for their localisation and in tension regulation. To this aim, we created artificial crosslinkers, for which I was able to modulate size independently of other features. We created artificial crosslinkers between 5 and 35 nm long, which successfully localised to actin structures. I investigated the role of artificial crosslinkers in the control of cortical thickness, tension and cell division. Together, in this thesis, I investigate new levels of regulation of cortical organisation and tension at the molecular level