Material damage to multielectrode arrays after electrolytic lesioning is insignificant

The quality of stable long-term recordings from chronically implanted electrode arrays is essential for experimental neuroscience and brain-computer interfaces. This work uses scanning electron microscopy (SEM) to image and analyze eight 96-channel Utah arrays previously implanted in motor cortical regions of four subjects (subject H = 2242 days implanted, F = 1875, U = 2680, C = 594), providing important contributions to a growing body of long-term implant research leveraging this imaging technology. Four of these arrays have been used in electrolytic lesioning experiments (H = 10 lesions, F = 1, U = 4, C = 1), a recently developed electrolytic perturbation technique demonstrated compatible with continued neuroelectrophysiology using small direct currents. Previously, our group showed that electrolytic lesioning can be used as a technique to create regions of controlled neuron loss without significantly changing recording quality (Bray, Clarke et al., 2024). Here, by surveying physical damage such as biological debris and material deterioration, we show that electrolytic lesioning causes no statistically significant material damage to the implanted electrode arrays. In addition to surveying physical damage, such as biological debris and material deterioration, this work also analyzes whether electrolytic lesioning created damage beyond what is typical for these arrays. These findings also indicate that there are no statistically significant differences between the damage observed on normal electrodes versus those used for electrolytic lesioning, yielding no evidence that electrolytic lesioning significantly affects the material quality of chronically implanted electrode arrays. Finally, this work also includes the largest collection of single-electrode SEM images for previously implanted multielectrode Utah arrays, spanning 11 different intact arrays and one broken array. As the clinical relevance of chronically implanted electrodes with single-neuron resolution continues to grow, these images may be used to provide the foundation for a larger public database and inform further electrode design and analyses.