From brain scans regarding psychedelic mushroom use, it shows a huge increase of brain activity, indicating a lot more neural activations, which is why visuals

From brain scans regarding psychedelic mushroom use, it shows a huge increase of brain activity, indicating a lot more neural activations, which is why visuals usually involve seeing resemblance of things you know in things like wall or carpet textures. There are also some reports that the blood flow to the region that is responsible for parsing reality is decreased and increased to other areas, which makes your internal thoughts feel more like reality. If you think about it in terms of neural networks, your day to day life is a set of standard inputs that result in predictable emotions/outcomes. However, on a shroom trip with significant dosage, both the outside effects and internal thoughts get enhanced in both strength and with additional features, which can be enough to start moving your internal synaptic weights enough to effect different thoughts or behaviors. This is analogous to something like going to a different country with a different culture, and living there, which in turn will change your perspectives opinions and behaviors based on experiencing life differently - after about a month or so you will likely be doing things slightly differently and thinking about concepts in a slightly different way. Magic mushrooms essentially condenses this process in a shorter timeframe. So given the right setting, this process can provide positive effects. Of course, the trip could also exaggerate negative emotions and thoughts, however, because of no withdrawal symptoms or long lasting effects, people generally just remember it as a bad trip and don't wanna do it again. Even there, sometimes the meta effect is experiencing the bad feeling strong enough during the trip that it doesn't seem as bad when you are sober. In general, the argument for use is that the probability for negative effects is low, but probability for positive effects is significant. So rationally it makes sense to go through the experience.