An instrument used to record the electrical impulses of the brain is called an:

I believe that the instrument used to record the electrical impulses of the brain is called the electroencephalograph.

An electroencephalograph is used for recording electrical brain activity a process known as electroencephalography which is an electrophysiological monitoring method to record electrical activity. It involves placing electrodes on the scalp, may be used to diagnose tumors of the brain, to study brain waves among other conditions.