Letters

Slumber science
Your October 24 issue featuring sleep research was very interesting and helpful. However, it did not cover any research being done — there may be none — relating to the human brain and modern changes to the nighttime environment. For most of human history, not much activity could take place at night. The diurnal cycle of light and darkness and the yearly seasons north and south of the equator must have had great influences on our development, response, brain activity and sleep.