Card 1 of 8: Hebbian Theory: Neurons That Fire Together, Wire Together
Hebb's 1949 rule is the closest thing neuroscience has to a founding law: neurons that fire together, wire together. Every habit, skill, and memory is this rule running on repeat.
Raichle kept seeing the same brain regions go quiet exactly when a task started, scan after scan. In 2001 he named what they were doing instead: the brain's default mode.
Researchers strapped accelerometers onto 100 four-to-seven-year-olds and both of their parents for a full year. The pattern that fell out was not subtle.
Your brain isn't the fixed hardware it feels like. It's closer to software that rewrites its own wiring based on what you repeatedly do and think.
Kleitman showed in the 1930s that body temperature, alertness, and sleep are not random — they follow a clock. Panda showed in the 2010s that when you eat and when you see light shifts that clock as strongly as when you sleep.
Cannon named fight-or-flight in 1915. Seven decades later LeDoux traced why you flinch at a stick that looks like a snake — the amygdala fires before visual cortex finishes identifying the object.
In Parma in 1996, electrodes in a monkey's premotor cortex spiked when the monkey grabbed a peanut — and, unprompted, when a researcher grabbed a peanut in front of it.
Waddington coined 'epigenetics' in 1942 for how the same genome produces different outcomes by context. Meaney showed in the 2000s that rat pups licked more by mothers grew different stress responses because of a chemical mark, not a different gene.