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.

In the realm of neuroscience, the study of psychedelics has long been a captivating yet enigmatic pursuit. It is only recently that research has started illuminating the intricate relationship between psychedelics, consciousness, and brain activity, revealing a fascinating interplay that extends beyond mere simple hallucinations and the geometric patterns that are commonly associated with these substances. Adding another layer of complexity, we must also take into account the contextual backdrop against which these experiences unfold – how we feel, where we are, and what’s around us – elements collectively called ‘set and setting’. All these factors make up a formidable research endeavour, with deep philosophical implications and convoluted technical challenges. How the outside world shapes inner experience not only informs how we can use set and setting therapeutically – it can also tell us about what that experience is and how it works.