“Calm down, relax, and breathe smoothly,” says a voice in your ear. Counting shapes on a screen will be difficult, the voice continues, because there is a block of wood in front of your eyes. “Just relax. It is easy for you to ignore everything but the wooden board.” But there is no wooden board – this is a hypnotic suggestion. Electroencephalography (EEG) measures the brain waves of a hypnotised woman wearing a cap full of electrodes. In the overall study, those who believed the wooden block was real had altered brain activity and struggled to count the shapes. But scientists noticed something else – brain waves accompanying the early stages of visual perception were not affected. This hints that hypnosis works deep in the brain, and that participants can still 'see' the shapes, but are powerless to process the information until the hypnotic spell is lifted.
BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.
BPoD is also available in Catalan at www.bpod.cat with translations by the University of Valencia.