We don't often think about what it means to...well...think.
In actuality, every single thought that goes through our minds involves a complex process involving stimulation, processing, and response. Neuroscientists have long understood how this works, but recently at UC Berkeley, they've finally been able to see it.
By recording the electrical activity of neurons directly from the surface of the brain, they were able to locate the parts of the brain that activate first, then follow that activity to the next location. It's totally amazing, and you can see it for yourself.
When a stimulus, such as a word, is given, the visual and auditory cortexes light up in reaction to the stimuli first.