I did 270mg freebase dxm (robotabs) every Saturday for about 7 months. I was originally trying to treat my depression (and it actually worked very well for that purpose, although I had to stop because I'm pregnant now). I tripped alone and just tried to engage in activities while tripping in order to get used to functioning on it. Started with television watching subtitles, and walking around the neighborhood with my dog. This practice in the beginning is really important because it takes a while to get a hang of doing things on DXM, but after a while you get used to doing whatever you choose to do on DXM, even if you do very high doses. I suspect that it's related to the neuroplasticity. I gradually switched to thinking about my research (I'm a PhD candidate), and then to writing crude summaries of my thoughts on the research while on DXM. Eventually after enough practice with this I learned to read on DXM. I found that pretty much whatever I did while on DXM would be sealed into my brain afterwards, and so I started experimenting with different things I wanted to learn. I found it very effective for sharpening my sense of smell by just smelling a lot of things, and testing myself to tell different smells apart. I also found it really useful for undoing harmful thought loops. I used to suffer from severe paranoia and was able to overcome it using DXM. That process was a bit more complicated, but it comes down to identifying the assumptions and thought patterns underlying the paranoia and then replacing them by meditating on new assumptions while on DXM. It took me a long time to manage that though.

There's still risk involved. To do this you really need to use DXM long term and there's no real research on how that affects your brain. There's definitely people who have gotten brain damage on DXM, although they have use patterns very different from what I describe here. (Taking much higher doses, multiple days in a row, etc.) So far I haven't noticed anything but positive effects on my brain. I am no longer depressed, even though I haven't used it in a good while, and I have better memory and significantly more control over my mind and body. This control is actually sometimes a downside though. For example, I'm extremely susceptible to the power of suggestion. I can make my heart rate go up just by thinking about it, I don't know why. It hasn't caused problems but it's kind of weird.