Abstract
Microelectrode arrays (MEAs) enable the recording of electrical activity from cortical neurons which has implications for basic neuroscience and neuroprosthetic applications. The design space for MEA technology is extremely wide where devices may vary with respect to the number of monolithic shanks as well as placement of microelectrode sites. In the present study, we examine the differences in recording ability between two different MEA configurations: single shank (SS) and multi-shank (MS), both of which consist of 16 recording sites implanted in the rat motor cortex. We observed a significant difference in the proportion of active microelectrode sites over the 8-week indwelling period, in which SS devices exhibited a consistent ability to record activity, in contrast to the MS arrays which showed a marked decrease in activity within 2 weeks post-implantation. Furthermore, this difference was revealed to be dependent on the depth at which the microelectrode sites were located and may be mediated by anatomical heterogeneity, as well as the distribution of inhibitory neurons within the cortical layers. Our results indicate that the implantation depth of microelectrodes within the cortex needs to be considered relative to the chronic performance characterization.
Highlights
To evaluate the differences in recording capabilities between single and multi-shank devices, electrophysiological data were recorded from rats implanted with either single shank (SS) (n = 5)
While signal-to-noise ratio (SNR) for both types of devices did decrease slightly over time, there were few differences seen between the two arrays, indicating that the diminished recorded activity for MS arrays may stem from a lack of nearby active neurons, rather than an inability to resolve the unit activity
While the effects of these novel design changes have been at the forefront of investigation for intracortical microelectrode arrays (MEAs), the influence of location of microelectrode sites has rarely been considered relative to performance
Summary
Intracortical microelectrode arrays (MEAs) are capable of recording the electrical activity of neurons within the cortex with high temporal and spatial resolution for single unit activity (SUA) [1], enabling a variety of brain-machine interface applications [2,3,4,5,6,7]. While a SS probe is capable of stimulating and recording at various depths throughout the cortex, the MS MEAs aim to spatially distribute the recording sites normal to the insertion plane. Szarowski et al performed a comprehensive analysis of brain histological responses to devices with varied MEA shank cross-sectional areas of 16,900, 10,000, and 5000 μm (among other physical properties) and reported that the initial tissue response is proportional to the device size, whereas the sustained response is most likely a result of tissue-material interactions [12].
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