Intracellular Neuronal Recording with Flexible Micro-machined Probe Implants

We present an implantable sub-micron silicon probe device, with flexible interconnects, that is capable of intracellular neuronal recording. The silicon probe device’s ability to penetrate and record from neurons in an isolated brain of the sea slug Tritonia diomedea was tested, and we demonstrate that, for the first time, an implantable device can record intracellular action potentials from a single neuron (Pd5 of the Tritonia brain). Our group has focused on intracellular neuronal recording with stand-alone silicon needles in the past. In this paper we present the integration of the needle, using standard microfabrication techniques, with a flexible interconnect to an aluminum base pad where electrical connections to the device can be made. Intracellular signals provide detailed information about the functioning of single neurons by directly tracking the transmembrane voltage, as opposed to only recording the field potentials caused by large changes in the transmembrane voltage as is the case in extra-cellular recordings. We have found that the silicon probes (needles) have lower impedances than the Ag/AgCl glass capillary electrodes used conventionally for similar intracellular recording purposes. The success of this prototype is a major step toward self-contained, implantable devices suited for intracellular neuronal recording from freely behaving animals.