It turns out that our ability to sleep through loud noises is the result of bundles of spindles in the brain, according to research funded by the Academy of Architecture for Health, the Faculty Guidelines Institute and the Center for Health Design. These bundles are produced by the thalamus gland and help protect areas of the brain responsible for sensing sound. The amount of spindles results in deep sleepers who are impervious to loud sounds like thunder or light sleepers who wake with every little sound. However, the reasons for increased spindle production were not detected. Results of the study were published in Current Biology.