Chronic optical access through a polished and reinforced thinned skull

The Pennsylvania State University, University Park, Pennsylvania, USA. 3Department of Neurosurgery, The Pennsylvania State University, University Park, Pennsylvania, USA. 4Gladstone Institute of Neurological Disease, University of California, San Francisco, San Francisco, California, USA. 5Department of Neurology, University of California, San Francisco, San Francisco, California, USA. 6Graduate Program in Neurosciences, University of California at San Diego, San Diego, California, USA. 7Center for Neural Circuits and Behavior, University of California at San Diego, San Diego, California, USA. Correspondence should be addressed to D.K. ([email protected]).