Does breath control exercises surrounded by the dampen dumb down the brain due to lower level of oxygen intake?

Answer:
No. It actually have the opposite effect. It have been particular to help you mentally focus better and concentrate for longer period of time.

A friend's son died doing that. Be careful, you can intervene out and drown.

He was 17, and a competitive swimmer. His stopwatch be still running by the pool when his father got home and found him.