‧ 450 BC: Greek physician Alcmaeon concludes that the brain is the central organ for sensation and not the heart, as previously believed by Aristotelian thinkers.
‧ 300 BC: The first detailed account of the structure of the brain is completed by Alexandrian biologists Herophilus and Erasistratus. They back Alcmaeon’s theory that the brain is the center of human intelligence.
‧ 1027: The oldest drawing of the nervous system is traced to Cairo. Ibn al-Haytham sketched a nose and two eyes and ran hollow nerves from the latter to the brain.
‧ 1400s: Leonardo da Vinci tries to discover the link between the senses and the soul by studying, and sketching, the brain of a dead ox.
‧ 1873: Italian physician Camillo Golgi develops the reazione nera, the “black reaction.” The simple mixture of potassium dichromate and silver nitrate gave scientists the ability to stain and highlight individual brain cells.
‧ 1890s: Spaniard Santiago Ramon y Cajal adapts Golgi’s method and proves the brain is a collection of individual but interconnected neurons.
‧ 1929: The EEG, electroencephalogram, is created by Swiss inventor Hans Berger. The technique is still used diagnostically in neurology and psychiatry.
‧ 1970s: Invention of magnetic resonance imaging (MRI), now used commonly for brain scans.
‧ 1970s: Neuroscientists use an enzyme called horseradish peroxidase to trace neural tracts in animal brains.
‧ 1974: US scientists Edward J. Hoffman and Michael E. Phelps invent positron emission tomography, enabling whole-body scans showing 3D images of functional processes in the body.
‧ 1990: Functional MRI is invented by Seiji Ogawa at Bell Laboratories in the US. The images reveal changes in blood flow in the brain over time.
‧ 2007: Jeff Lichtman at Harvard University adds fluorescence genes into growing neurons to produce spectacular multicolored “brainbows.”