In the 1950s, a study from McGill University subjected volunteers to "near-total sensory deprivation."One participant saw "nothing but dogs." Another, a "green horse." One heard a "music box playing" and one heard a "choir singing in full stereophonic sound."

Like the name suggests, sleep deprivation involves keeping prisoners awake for long periods of time. U.S. Justice Department memos released in 2009 found the CIA kept prisoners awake for as long as 11 days.  (Video via National Geographic)

Perhaps the most controversial and most widely publicized of all methods, waterboarding works by tricking a person's brain into believing he or she is drowning. The prisoner lies on an inclined platform like this.

Water is poured through the mouth and nose or on top of cellophane covering the prisoner's face. The lungs don't fill with water but feel like they do. (Video via Vanity Fair)

According to the report, during one session, Saudi Arabian prisoner Abu Zubaydah became "completely unresponsive with bubbles rising through his open full mouth."

This video includes an image from Karl Gunnarsson / CC BY SA 2.0 and the U.S. Department of Defense.