Biology subjects

Schelles, M.

Publications and source records attributed to Schelles, M..

2 recordsLinked to original sources

bioRxiv2026

Polymer-based flexible multi-shank probes for simultaneous intracortical microstimulation and two-photon calcium imaging

Intracortical microstimulation is an essential tool for basic neuroscience and sensory restoration, yet the spatiotemporal effects of advanced multielectrode stimulation strategies on cortical networks remain poorly understood. This study presents a versatile experimental platform featuring polymer-based, flexible multi-shank electrode arrays integrated with a custom high-density neurostimulator. The polyimide penetrating probes contain densely spaced iridium oxide microelectrodes on thin, flexible shanks with sharp tips designed to minimize mechanical mismatch, tissue damage, and brain dimpling. The system was validated in transgenic GCaMP6 mice through simultaneous two-photon calcium imaging and electrical stimulation in layer 2/3 of the visual cortex. Monopolar stimulation reliably evoked robust, parameter-dependent neuronal activation, with neuronal recruitment increasing as a function of current intensity and pulse duration. Bipolar stimulation produced activation patterns distinct from monopolar stimulation, with neuronal responses that were more spatially confined when bipolar electrodes were positioned in close proximity. Furthermore, static current steering--implemented by varying the current ratio between the selected electrode pair--successfully shifted the centroid of activated neuronal populations, enabling fine spatial control over the site of activation. The developed platform provides a flexible framework for investigating local neuronal responses to complex electrical stimulation paradigms, facilitating the development of neural prostheses with higher spatial precision.

neuroscience↗

bioRxiv2025

Intracortical bipolar stimulation allows selective activation of neuronal populations in the cortex

BackgroundIntracortical electrical stimulation has emerged as a promising approach for sensory restoration, such as a cortical visual prosthesis, yet its effectiveness is limited by current spread and electrode density constraints. ObjectiveTo determine whether intracortical bipolar current steering--via modulation of the return electrode position--can enhance neural activation selectivity compared to traditional monopolar stimulation, with the aim of improving spatial precision in sensory restoration. MethodsWe applied intracortical stimulation and used two-photon calcium imaging on acute brain slices to directly visualize neural responses to bipolar stimulation. Biophysical computational modeling was used to complement the experimental results. The analysis included both cellular and population-level assessments to evaluate the impact of several stimulation patterns, such as current direction, electrode spacing and current amplitude, on recruitment patterns. ResultsBipolar stimulation selectively activated distinct neural populations based on the direction of the current flow. This approach decreased the overlap between activated groups and increased the number of independently addressable neural clusters by up to 9-fold relative to monopolar stimulation. Moreover, the electrode configuration and spacing critically influenced the spatial spread of activation. ConclusionsIntracortical bipolar current steering enhances neural activation selectivity by engaging independent neural populations through current directionality. These findings suggest that this strategy may improve the spatial precision of neural prosthetics and sensory restoration without the need for an increased electrode density.

neuroscience↗