Following analysis of the fluorescence in the brain sections, the samples were fixed overnight in 4 % neutral buffered formaldehyde. Research Pathology Services at the Geisel School of Medicine at Dartmouth College prepared the following histopathology and immunohistochemistry tissue sections. Formalin-fixed tissues were dehydrated using crescent concentrations (70–100 %) of alcohol (Fisher Scientific, USA), cleared with xylene (Cat # X3P-1GAL, Fisher Scientific, USA) and embedded in paraffin (Cat # 7052, Sakura Finetek, Torrance, CA, USA). The brain sections were cut to 4-μm thickness and stained with hematoxylin and eosin (H&E) and for total EGFR using an anti-EGFR primary antibody (EP38Y) (Cat # ab52894; Abcam Inc., Cambridge, MA, USA) (immunohistochemistry).