High-Channel-Count Impedance Spectroscopy Logger

Abstract

Investigating intracerebral tissue at single cell level has become increasingly important in animal studies and meanwhile found its way into clinical applications. The stability of single unit activity (SUA) to be recorded can be however quite elusive, which -among others- might be caused by the mechanical mismatch of stiff neural implants and soft brain tissue. Unfortunately, the variety of factors influencing signal degradation over time are not perfectly understood yet. One opportunity to determine degradation onsets and possibly identify relevant mechanisms influencing signal stability is impedance spectroscopy of the electrode-brain interface. In particular in view of high-channel count electrode arrays used in neuroscientific research, an impedance spectroscopy analyzer is needed, capable of non-destructively and continuously measuring impedance spectra of a large number of electrodes. The measurement system developed in the current study allows determining the impedance spectra from up to 1024 channels with low uncertainty and an accuracy within a 15%-window over a wide range of impedance values.