For those - I was one - doubting that breathing can have any effect in brain activity, you would be surprised to know that voluntary hyperventilation is a common tool to diagnose epilepsy[1].

My kid went through a battery of tests that included light - no reaction - and hyperventilation - that triggered some jerky movements in his legs and a clear alteration of the EEG readings.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6546426/