Later people started cutting holes in the skulls of other people, a process called trephaning. This was done to release evil spirits or help heal a head injury, and surprisingly enough, the patients often survived and may have had several holes cut in their skull before they finally died. Still later, Aristotle claimed that the brain was just a large "radiator" for cooling the blood, and Descartes claimed that the important parts of the brain were the ventricles (fluid-filled parts of the brain, they were thought to litterally "pump you up" because the nerves were believed to be hollow tubes) and the pineal gland (where the soul resided).
Then the day finally came when it was realized that the actual matter of the brain was the important part and that nerves were kind of like electrical wires. This was discovered mostly by simply hacking parts of the brain out, a process called ablation, and then observing the results. One scientist named Flourens did this a lot on cats and birds using a common mellon baller type scoop. But techniques and equipment got better, and new approches were used. Often times the brain was exposed and the cortex, or surface, was electrically stimulated. If the right place was stimulated, movement could be produced. (However, it appeared that nothing happened when the rest of the cortex was stimulated, which is why the myth exists today that we only use ten percent of our brains. But when you are using anaesthatized dogs, it is hard for them to tell you that they are feeling or seeing or hearing something.)
To make a long story short, techniques kept improving, and now scientists can record the electrical activity of a single neuron or "take a picture" of your brain while you perform some activity to see what parts you are using the most. Amazing.