NeuroGrid: recording action potentials from the surface of the brain

In this technical report, Khodagholy and colleagues find that NeuroGrid, a planar, scalable and highly conformable electrode array, allows recordings of local-field potentials and stable single-unit activity from the surface of the rat cortex or hippocampus. The authors also validate NeuroGrid across species by showing that that it can capture LFP-modulated spiking activity intraoperatively in surgical patients, thus demonstrating its utility as tool for fundamental research on the human brain and in the clinic. Recording from neural networks at the resolution of action potentials is critical for understanding how information is processed in the brain. Here, we address this challenge by developing an organic material–based, ultraconformable, biocompatible and scalable neural interface array (the ‘NeuroGrid’) that can record both local field potentials(LFPs) and action potentials from superficial cortical neurons without penetrating the brain surface. Spikes with features of interneurons and pyramidal cells were simultaneously acquired by multiple neighboring electrodes of the NeuroGrid, allowing for the isolation of putative single neurons in rats. Spiking activity demonstrated consistent phase modulation by ongoing brain oscillations and was stable in recordings exceeding 1 week's duration. We also recorded LFP-modulated spiking activity intraoperatively in patients undergoing epilepsy surgery. The NeuroGrid constitutes an effective method for large-scale, stable recording of neuronal spikes in concert with local population synaptic activity, enhancing comprehension of neural processes across spatiotemporal scales and potentially facilitating diagnosis and therapy for brain disorders.