My protagonist, a victim of a similar accident from my previous question, looks and acts the same on the outside, while being very different on the inside. In this question however, the main informations are: his nervous system and body allow him to react and function normally at Mach 50 (his body can take the consequences of doing so and has a much longer potential lifespan, so he ages at what'd be considered normal rate, additionally his nervous signals travel at much faster speeds than in a normal human). The main issue with this however is that functioning all the time at that speed makes him essentially incapable of functioning normally by human standards, moving will cause destruction and interaction with others is almost impossible due to how slow they seem.
Based on this and to solve such an issue, is there a biological way for my character to be capable of slowing down his overall perception of time caused by his speed?. Though his different biology could allow me to stretch a "yes", I'd like to know if one can actually, to some degree, slow down their processing and reaction speed. My original approach was having him naturally function at a slightly slower speed and grant him certain control over his metabolism, since this was the best natural response I've found, with the reduction in brain activity as a byproduct of a lower metabolism, but it doesn't quite match what I need, as it wouldn't really slow down his processing speed (it does somewhat reduce the brain's capacity overall, but it also has a fair share of unwanted side-effects, including headaches, concentration problems and others, and a hypermetabolism didn't turn out to be a good approach either).