Recording of Network-Wide Intracellular Activity and Mapping of Synaptic Connections Using Microhole Electrode Arrays

Abstract

Network-wide parallelization of neuronal intracellular recording and quantification of synaptic connections and their strengths is a challenge still open in neuroscience, with a mapping limit of ~300 connections. Here, we report a 4,096 microhole electrode array on a semiconductor chip for parallel intracellular recording and synaptic connectivity mapping of rat neuronal cultures using electroporation. The microholes are etched from a complementary metal-oxide semiconductor chip, and the final surface is coated with platinum black to increase roughness and the neuronal interface. The microhole array allows up to 90% average intracellular coupling rate with high coupling fidelity, generating network-wide intracellular recording data containing synaptic signals, and allows regaining intracellular coupling on the same neurons. We extract 70,000+ plausible synaptic connections amongst 2,000+ neurons, and catalogue them into inhibitory, weak/uneventful excitatory, strong/eventful excitatory chemical synaptic connections, and electrical synaptic connections, with an estimated overall error rate of around 5%. The reported scale of chemical and electrical synaptic mapping combines the advantages of patch clamp and extracellular multi-electrode array recordings, providing valuable insights into large-scale neural connectivity.