Brainwaves. Abstract illustration of a spiked waveform and the human brain, depicting a thought pattern or some mental state. It may also repre- sent headache or the pain of migraine. Electrical impulses are produced by the activity of the brain when measured on an EEG (electro-encephalogram). Such wave patterns alter when awake, asleep, or undergoing thought processes. At above centre, the folded cerebrum of the brain can be seen: this largest area of the brain is concerned with con- scious thought, sensation and movement. Below centre, the brainstem (attaches the spinal cord) and cerebellum (at right) are involved in uncons- cious body functions of breathing and balance.