Cortical Brain Stimulation with Endovascular Electrodes.

Electrical stimulation of neural tissue and recording of neural activity are the bases of emerging prostheses and treatments for spinal cord injury, stroke, sensory deficits, and drug-resistant neurological disorders. Safety and efficacy are key aspects for the clinical acceptance of therapeutic neural stimulators. The cortical vasculature has been shown to be a safe site for implantation of electrodes for chronically recording neural activity, requiring no craniotomy to access high-bandwidth, intracranial EEG. This work presents the first characterization of endovascular cortical stimulation measured using cortical subdural surface recordings. Visual stimulation was used to verify electrode viability and cortical activation was compared with electrically evoked activity. Due to direct activation of the neural tissue, the latency of responses to electrical stimulation was shorter than for that of visual stimulation. We also found that the center of neural activation was different for visual and electrical stimulation indicating an ability of the stentrode to provide localized activation of neural tissue.

Current steering for high resolution retinal implants.

To significantly increase the resolution achievable by a retinal prosthesis without requiring additional electrodes, a current steering technique could be utilized. In this study, a finite element model was constructed to analyze the local concentrations of charge carrying ions within a saline bath due to concurrent stimulation from two electrodes surrounded by a hexagonal arrangement of return electrodes. By altering the return pathways, tissue activation and identification of unique stimulation patterns is possible. Ag/Ag-Cl electrodes and a voltage controlled current source were developed to validate the finite element model, with the model accurately predicting saline bath measurements. The average error in the returned currents between the finite element model and experimental results was 2% relative to the stimulus current.