1. Neuroregulation Group, Department of Neurosurgery, Leiden University Medical Centre (LUMC), P.O. Box 9600, NL‐2300 RC Leiden, the Netherlands
2. Department of Polymer Chemistry and Biomaterials, Institute for Biomedical Technology (BMTI), University of Twente, P.O. Box 217, NL‐7500 AE Enschede, the Netherlands
3. Department of Neurophysiology, Leiden University Medical Centre (LUMC), P.O. Box 9600, NL‐2300 RC Leiden, the Netherlands