Instrumentation to evaluate neural signal recording properties of micromachined microelectrodes inserted in invertebrate nerve

The design and characterization of instrumentation for application in evaluating the neural signal recording properties of probe-type microelectrodes, micromachined from silicon, are reported. Key aspects include the close matching of gain and frequency response between channels (better than 1%), flexibility in signal conditioning options, the ability to operate with a wide range of (microelectrode) recording site dimensions (4 mum x 4 mum to 50 mum x 50 mum), and hence impedances, and the facility to monitor and store instrumentation settings on computer along with the recorded signals. Noise levels ranged from 3.7 muV rms for a 50 mum site, to 11.7 muV rms for a 4 mum site, measured in saline. Close matching between channels was required to enable comparisons between different sites and different probes to be made with confidence; however, the instrumentation could be readily applied to less demanding applications.