design-surface-treatment-cellular-plating-culturing-modular-neuronal

Design, Surface Treatment, Cellular Plating, and Culturing of Modular Neuronal Networks Composed of Functionally Inter-connected Circuits

The brain operates through the coordinated activation and the dynamic communication of neuronal assemblies. A major open question is how a vast repertoire ...

Istituto Italiano di Tecnologia

Behaviors, from simple to most complex, require a two-way interaction with the environment and the contribution of different brain areas depending on the orchestrated activation of neuronal assemblies. In this work we present a new hybrid neuro-robotic architecture based on a neural controller bi-directionally connected to a virtual robot implementing a Braitenberg vehicle aimed at avoiding obstacles. The robot is characterized by proximity sensors and wheels, allowing it to navigate into a circular arena with obstacles of different sizes. As neural controller, we used hippocampal cultures dissociated from embryonic rats and kept alive over Micro Electrode Arrays (MEAs) for 3-8 weeks. The developed software architecture guarantees a bi-directional exchange of information between the natural and the artificial part by means of simple linear coding/decoding schemes. We used two different kinds of experimental preparation: "random" and "modular" populations. In the second case, the confinement was assured by a polydimethylsiloxane (PDMS) mask placed over the surface of the MEA device, thus defining two populations interconnected via specific microchannels. The main results of our study are: (i) neuronal cultures can be successfully interfaced to an artificial agent; (ii) modular networks show a different dynamics with respect to random culture, both in terms of spontaneous and evoked electrophysiological patterns; (iii) the robot performs better if a reinforcement learning paradigm (i.e., a tetanic stimulation delivered to the network following each collision) is activated, regardless of the modularity of the culture; (iv) the robot controlled by the modular network further enhances its capabilities in avoiding obstacles during the short-term plasticity trial. The developed paradigm offers a new framework for studying, in simplified model systems, neuro-artificial bi-directional interfaces for the development of new strategies for brain-machine interaction.

Modular neuronal assemblies embodied in a closed-loop environment: toward future integration of brains and machines.

Brain-machine interfaces (BMI) were born to control "actions from thoughts" in order to recover motor capability of patients with impaired functional connectivity between the central and peripheral nervous system. The final goal of our studies is the development of a new proof-of-concept BMI-a neuromorphic chip for brain repair-to reproduce the functional organization of a damaged part of the central nervous system. To reach this ambitious goal, we implemented a multidisciplinary "bottom-up" approach in which in vitro networks are the paradigm for the development of an in silico model to be incorporated into a neuromorphic device. In this paper we present the overall strategy and focus on the different building blocks of our studies: (i) the experimental characterization and modeling of "finite size networks" which represent the smallest and most general self-organized circuits capable of generating spontaneous collective dynamics; (ii) the induction of lesions in neuronal networks and the whole brain preparation with special attention on the impact on the functional organization of the circuits; (iii) the first production of a neuromorphic chip able to implement a real-time model of neuronal networks. A dynamical characterization of the finite size circuits with single cell resolution is provided. A neural network model based on Izhikevich neurons was able to replicate the experimental observations. Changes in the dynamics of the neuronal circuits induced by optical and ischemic lesions are presented respectively for in vitro neuronal networks and for a whole brain preparation. Finally the implementation of a neuromorphic chip reproducing the network dynamics in quasi-real time (10 ns precision) is presented.

In vitro large-scale experimental and theoretical studies for the realization of bi-directional brain-prostheses.

Les interfaces cerveau-machine (IMC) sont n&eacute;s au contr&ocirc;le &laquo; des actions de pens&eacute;es &raquo; afin de r&eacute;cup&eacute;rer le moteur capacit&eacute; des patients avec une d&eacute;ficience connectivit&eacute; fonctionnelle entre le syst&egrave;me nerveux central et p&eacute;riph&eacute;rique. L&#39;objectif final de nos travaux est l&#39;&eacute;laboration d&#39;une nouvelle puce de validation, un IMC neuromorphic pour cerveau-r&eacute;paration &agrave; reproduire l&#39;organisation fonctionnelle d&#39;une partie endommag&eacute;e du syst&egrave;me nerveux central. Pour atteindre cet objectif ambitieux, nous avons impl&eacute;ment&eacute; une approche multidisciplinaire de la &laquo; bottom-up &raquo; dans laquelle les r&eacute;seaux in vitro sont le paradigme pour le d&eacute;veloppement d&#39;un in silico mod&egrave;le &ecirc;tre int&eacute;gr&eacute;e &agrave; un dispositif neuromorphic. Dans cet article, nous pr&eacute;sentons la strat&eacute;gie globale et mettre l&#39;accent sur les diff&eacute;rents &eacute;l&eacute;ments constitutifs de nos &eacute;tudes: (i) l&#39;exp&eacute;rimental caract&eacute;risation et mod&eacute;lisation des &laquo; r&eacute;seaux de taille finie &raquo;, qui repr&eacute;sentent les circuits auto-organis&eacute;e plus petits et plus g&eacute;n&eacute;rales capables de g&eacute;n&eacute;rer une dynamique collective spontan&eacute;e ; (ii) l&#39;induction des l&eacute;sions dans les r&eacute;seaux de neurones et la pr&eacute;paration du cerveau entier avec une attention particuli&egrave;re sur l&#39;impact sur l&#39;organisation fonctionnelle des circuits ; (iii) la premi&egrave;re production d&#39;une puce neuromorphic capable d&#39;appliquer un mod&egrave;le en temps r&eacute;el des r&eacute;seaux neurones. Une caract&eacute;risation dynamique des circuits taille finie avec r&eacute;solution unicellulaire est fournie. Un mod&egrave;le de r&eacute;seau neuronal bas&eacute; sur neurones d&#39;izhikevich a &eacute;t&eacute; en mesure de reproduire les observations exp&eacute;rimentales. Changements dans la dynamique des circuits neuronaux induits par des l&eacute;sions isch&eacute;miques et optiques sont pr&eacute;sent&eacute;s respectivement pour les r&eacute;seaux de neurones in vitro et pour une pr&eacute;paration de tout le cerveau. Enfin, la mise en &oelig;uvre d&#39;une puce neuromorphic reproduisant la dynamique du r&eacute;seau en temps quasi r&eacute;el (pr&eacute;cision de 10 ns) est pr&eacute;sent&eacute;.

&Eacute;tudes in vitro &agrave; grande &eacute;chelle exp&eacute;rimentales et th&eacute;oriques pour la r&eacute;alisation de bi-directional cerveau-proth&egrave;ses.

Interfacce cervello-macchina (BMI) sono nati a controllo &quot;azioni da pensieri&quot; al fine di recuperare la motricit&agrave; dei pazienti con alterata connettivit&agrave; funzionale tra il sistema nervoso centrale e periferico. L&#39;obiettivo finale dei nostri studi &egrave; lo sviluppo di un nuovo chip di proof-of-concept, un BMI neuromorphic per riparazione di cervello-a riprodurre l&#39;organizzazione funzionale di una parte danneggiata del sistema nervoso centrale. Per raggiungere questo ambizioso obiettivo, abbiamo implementato un approccio &quot;bottom-up&quot; multidisciplinare in cui le reti in vitro sono il paradigma per lo sviluppo di un in silico modello ad essere incorporati in un dispositivo di neuromorphic. In questo libro ci presenta la strategia complessiva e concentrarsi sui diversi blocchi dei nostri studi: (i) la sperimentale caratterizzazione e modellazione delle &quot;reti di dimensione finita&quot;, che rappresentano i circuiti auto-organizzati pi&ugrave; piccoli e pi&ugrave; generali in grado di generare dinamiche collettive spontanee; (ii) l&#39;induzione di lesioni in reti neuronali e la preparazione del cervello intero con speciale attenzione all&#39;impatto sull&#39;organizzazione funzionale dei circuiti; (iii) la prima produzione di un chip di neuromorphic in grado di implementare un modello in tempo reale delle reti neuronali. Viene fornita una caratterizzazione dinamica dei circuiti di dimensione finita con risoluzione della singola cella. Un modello di rete neurale basato su neuroni Izhikevich era in grado di replicare alle osservazioni sperimentali. Cambiamenti nella dinamica dei circuiti neuronali indotti da lesioni ischemiche e ottiche sono presentati rispettivamente per le reti neuronali in vitro e per una preparazione intero cervello. Infine l&#39;implementazione di un chip neuromorphic riproducendo le dinamiche di rete in tempo quasi-real (precisione 10 ns) &egrave; presentato.

Studi in vitro su larga scala teorici e sperimentali per la realizzazione del cervello-protesi bi-direzionale.

Uniform and modular primary hippocampal cultures from embryonic rats were grown on commercially available micro-electrode arrays to investigate network activity with respect to development and integration of different neuronal populations. Modular networks consisting of two confined active and inter-connected sub-populations of neurons were realized by means of bi-compartmental polydimethylsiloxane structures. Spontaneous activity in both uniform and modular cultures was periodically monitored, from three up to eight weeks after plating. Compared to uniform cultures and despite lower cellular density, modular networks interestingly showed higher firing rates at earlier developmental stages, and network-wide firing and bursting statistics were less variable over time. Although globally less correlated than uniform cultures, modular networks exhibited also higher intra-cluster than inter-cluster correlations, thus demonstrating that segregation and integration of activity coexisted in this simple yet powerful in vitro model. Finally, the peculiar synchronized bursting activity shown by confined modular networks preferentially propagated within one of the two compartments ('dominant'), even in cases of perfect balance of firing rate between the two sub-populations. This dominance was generally maintained during the entire monitored developmental frame, thus suggesting that the implementation of this hierarchy arose from early network development.

Article	Year
Modular neuronal assemblies embodied in a closed-loop environment: toward future integration of brains and machines. Frontiers in neural circuits\| PubMed ID: 23248586	2012
In vitro large-scale experimental and theoretical studies for the realization of bi-directional brain-prostheses. Frontiers in neural circuits\| PubMed ID: 23503997	2013
Emergence of bursting activity in connected neuronal sub-populations. PloS one\| PubMed ID: 25250616	2014

Marta Bisio

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