In a second group of mice, Dr. Turner’s team activated the dorsal medial habenula using optogenetics – a precise laser technology developed in collaboration with the Allen Institute for Brain Science. The mice could “choose” to activate this area of the brain by turning one of two response wheels with their paws. The mice strongly preferred turning the wheel that stimulated the dorsal medial habenula, demonstrating that this area of the brain is tied to rewarding behavior.