Experimental Platform to Study Spiking Pattern Propagation in Modular Networks In Vitro

Abstract

The structured organization of connectivity in neural networks is associated with highly efficient information propagation and processing in the brain, in contrast with disordered homogeneous network architectures. Using microfluidic methods, we engineered modular networks of cultures using dissociated cells with unidirectional synaptic connections formed by asymmetric microchannels. The complexity of the microchannel geometry defined the strength of the synaptic connectivity and the properties of spiking activity propagation. In this study, we developed an experimental platform to study the effects of synaptic plasticity on a network level with predefined locations of unidirectionally connected cellular assemblies using multisite extracellular electrophysiology.

Structure-Function Dynamics of Engineered, Modular Neuronal Networks with Controllable Afferent-Efferent Connectivity

“…in 2011, demonstrating that a design with narrower inlets at the postsynaptic side effectively reduced the chance of axons growing into the microchannels so that mainly axons from the presynaptic populations filled up the channels(6). Others have used variations of bottlenecks and traps inside the channels to coax the axons from the postsynaptic population away from the main channels and make them retract(7–10).…”

“…The first documented attempt at promoting unidirectional axon growth in this way was made by Peyrin et al in 2011, demonstrating that a design with narrower inlets at the postsynaptic side effectively reduced the chance of axons growing into the microchannels so that mainly axons from the presynaptic populations filled up the channels (6). Others have used variations of bottlenecks and traps inside the channels to coax the axons from the postsynaptic population away from the main channels and make them retract (7)(8)(9)(10). More recent studies have steered the afferent-efferent connectivity by implementing topographical features within the microchannels that guide the neurites from the presynaptic population through the channels, while the axons from the postsynaptic population are guided away from the main channels and back to their chamber of origin (11)(12)(13)).…”

“…Intrinsic axonal growth and guidance programs combined with cues from the microenvironment enable the growth cone at the tip of axons and their collaterals to probe their environment as part of axonal pathfinding (3,5). Over the past decade, a growing body of literature has demonstrated the effectiveness of microfluidic devices with geometrical constraints implemented within the microchannel architecture to steer the directionality of axonal outgrowth in vitro (6)(7)(8)(9)(10)(11)(12)(13). This is used to promote axonal outgrowth in a single direction, while outgrowth in the opposite direction is impeded (14).…”

“…To allow cell populations to be plated concurrently, more recent studies have rather focused on manipulating the microenvironment of the cells to spatially control the growth dynamics of the neuronal assemblies. Over the past decade, several studies have demonstrated the effectiveness of microfluidic devices with geometrical constraints implemented within the microchannel architecture to steer the directionality of axonal outgrowth in vitro (9)(10)(11)(12)(13)(14)(15)(16)(17). Specific geometries embedded within the microchannels are used to promote axonal outgrowth in a single direction, while outgrowth in the opposite direction is impeded (18).…”

“…An alternative approach has been to implement bottlenecks and traps inside the channels to coax the axons from the postsynaptic population away from the main channels and make them retract (10)(11)(12)(13). A challenge with this approach is that it can cause axonal fragmentation and lead to debris build up inside the channels.…”