Verification of multichannel electrode array integrity by use of cross-channel correlations

•Use of multi-channel electrode arrays (MEAs) for extracellular recording requires knowledge of the location and functional status of each channel.•Experience with recordings from our own and other laboratories suggests that shorted and mislocalised channels are often undetected.•Measurements of channel impedances prior to recording do not always identify problems, or those that arise after testing.•Our method presents to the user, immediately prior to spike-sorting, with a list of potentially problematic channels.•Correction of these errors by masking or re-labelling channels can improve subsequent spike sorting.

BackgroundThe use of multichannel electrode arrays (MEAs) presents a number of practical challenges to experimenters including correctly labelling different recording channel locations and identifying sites that may be non-functional or short-circuited. These challenges are likely to increase as the number of sites used in recording increases.New methodThis paper presents a simple method for assessing MEA integrity based on the observation that physiologically induced signal correlations between nearby channels fall off with distance. Channels that violate this relationship are flagged as being potentially problematic.ResultsThe method is able to present to the user a list of potentially faulty channels for further inspection. Underlying problems include non-functional, shorted and mislocalised channels and channels carrying spurious noisy signals unrelated to those on other channels.Comparison with existing methodsComputational methods which automatically screen MEAs for faulty electrode channels do not appear to exist in the literature. Currently a user would have to examine single channels, or channel pairs, individually, which would be very time-consuming.ConclusionsShorted or mislocalised channels may be more prevalent in MEA recordings than users suspect. The paper presents a simple screening method for identifying such channels prior to carrying out spike-sorting.