Debated for centuries, the human mind still holds a mystery or two in modern times. Here are LiveScience's top 10:
- Consciousness. Still the biggest human puzzle since Socrates.
- Cryonics. Can gray matter be revived from a 320-degree deep freeze?
- Aging. An unappreciated benefit, or simply cell decay with no purpose?
- Nature/nurture. DNA, peer pressure, upbringing—scientists disagree on why we do the things we do.
- Laughter. Three brain zones like it, but scientists wonder why people giggle at different things.
- Memories. Scientists have spotted the brain's memory regions, but true and false memories mysteriously zap the same gray matter.
- Biological clock. Melatonin alters it; could supplements of the hormone reduce jet lag?
- Missing limb feelings. Nerves may relink to the spinal cord—unless the brain is permanently hardwired to think we're all there.
- Sleeping. A time for brain hibernation, or the cataloging of memories?
- Dreaming. Are synapses exercising as we dream, or are feelings being worked out?