Characterization of Axonal Spikes in Cultured Neuronal Networks Using Microelectrode Arrays and Microchannel Devices

Axonal propagation has a pivotal role in information processing in the brain. However, there has been little experimental study due to the difficulty of isolation of axons and recording their signals. Here, we developed dual chamber neuronal network interconnected with axons by integrating microchannel devices with microelectrode arrays (MEAs) to investigate axonal signals in developmental stage.

The device was composed of two chambers and microchannels between them, and hippocampal neurons were cultured in both chambers. Neuronal activity was recorded for four weeks.

Large axonal signal was detected in microchannels, which were 137.0 ± 8.5 μV at 14 days in vitro (DIV). It was significantly larger than those in chambers with a similar range of signal-to-noise ratio. Detection efficiency of axonal spikes was analyzed by calculating the number of active electrodes over time. We found that active electrodes were detected earlier and their number increased faster in microchannels than those in chambers. Finally, we estimated the axonal conduction velocity and 73% of axons had the velocity in range of 0.2-0.5 m/s at 14 DIV. By estimating the velocity over the cultivation period, we observed that axonal conduction velocity increased linearly over time.

Using MEAs and microchannel devices, we successfully detected large axonal signals and analyzed their detection efficiency and conduction velocity. We first showed the gradual increase in conduction velocity depending on cultivation days.

The developed microchannel device integrated MEA may be applicable for the studies of axonal conduction in cultured neuronal networks.