Reliable neuronal logic devices from patterned hippocampal cultures

Functional logical microcircuits are an essential building block of computation in the brain. However, single neuronal connections are unreliable, and it is unclear how neuronal ensembles can be constructed to achieve high response fidelity. Here, we show that reliable, mesoscale logical devices can be created in vitro by geometrical design of neural cultures. We control the connections and activity by assembling living neural networks on quasi-one-dimensional configurations. The linear geometry yields reliable transmission lines. Incorporating thin lines creates 'threshold' devices and logical 'AND gates'. Breaking the symmetry of transmission makes neuronal 'diodes'. All of these function with error rates well below that of a single connection. The von Neumann model of redundancy and error correction accounts well for all of the devices, giving a quantitative estimate for the reliability of a neuronal connection and of threshold devices. These neuronal devices may contribute to the implementation of computation in vitro and, ultimately, to its understanding in vivo.