No doubt, it does occur. Do I feel as sharp at 51 as I did at 25? No. It seems to take longer to pick-up new things. I'm struggling a bit with Rust but I picked up Python the last few weeks with no problem. Clojure, I still can't grok the functional paradigm. Maybe BASIC did ruin me. Programming a PIC in assembly, no problem. I learned early in my career that you must continually study. I take online training a couple of times a month and read and practice a lot. That is key I think, if you wish to stay in programming, and not move into the management track.