"Mendel Kaelen, a Dutch postdoc in the Imperial lab, proposes a more extended snow metaphor: "Think of the brain as a hill covered in snow, and thoughts as sleds gliding down that hill. As one sled after another goes down the hill, a small number of main trails will appear in the snow. And every time a new sled goes down, it will be drawn into the preexisting trails, almost like a magnet." Those main trails represent the most well-traveled neural connections in your brain, many of them passing through the default mode network. "In time, it becomes more and more difficult to glide down the hill on any other path or in a different direction. "Think of psychedelics as temporarily flattening the snow. The deeply worn trails disappear, and suddenly the sled can go in other directions, exploring new landscapes and, literally, creating new pathways." When the snow is freshest, the mind is most impressionable, and the slightest nudge--whether from a song or an intention or a therapist's suggestion--can powerfully influence its future course. Robin Carhart-Harris's theory of"