We think the world activates our brain to create experience but recent research into psychedelics suggests the reverse is sometimes true. External stimuli can mute brain activity. The brain is busy filtering reality when faced with the world. Take the world away, and the brain can go to new and exciting places, writes Pedro Mediano.

Most scientists seek to understand the world around us. Other scientists, like myself, seek to explain the world within us – the elusive nature of the human mind, the physical basis of consciousness, and the seemingly impenetrable barrier between external reality and first-person experience. Therefore, as consciousness neuroscientists, our task is to elucidate how our consciousness is altered in response to changes in our brain and our environment. And there is no alteration quite as powerful and encompassing as that elicited by psychedelic substances.