Most important takeaway: Even just paying attention to your breath has an impact on your brain. That said, how about 2 minutes with your eyes closed just paying attention to your breath right now? 3, 2, 1 Go.
This article summarizes research published in September that measured the impact of conscious breath practices on the brain. Unique in this study was that they measured with implanted electrodes (placed on the brain), not via inferring activity based on electrical impulses measured outside the skull. It's an interesting summary that includes a link to the full research paper.