With the advent of brain imaging technology such as MRI, positron emission tomography (PET) scans, and single proton emission computed tomography (SPECT) scans, scientists no longer have to guess what's going on in your brain. While they can't see your actual thought process, they are able to measure the size, shape, and symmetry of your brain and compare it against the brains of people who don't have ADHD.

However, researchers still don't know what causes “bad connections” in the brains of ADHD people. Is it caused by a smaller-sized brain or one that's not quite symmetrical? Do connections somehow misfire and get lost? Or is it a problem with our neurotransmitters, our brain's miniscule messengers?

Despite the dramatic increase in research, many answers continue to elude scientists, although they have made one major discovery. Using MRIs to scan the brains of people with ADHD, researchers have discovered that four regions in their brains are smaller than in “normal” brains.

A Look Inside Your Brain

Those four regions of the brain include the frontal lobes, the corpus collosum, the basal ganglia, and the cerebellum.

The frontal lobes are critical for executive functions like planning and organizing. Researchers already know that damage to the frontal lobes resulting from injury can result in mood swings, impulsivity, lack of inhibition, and hyperactivity.

The corpus collosum is the rope of nerves that connects the two hemispheres of your brain. Studies have shown that this area of the brain, besides being smaller in people with ADHD, also operates differently than in those who don't have the disorder.

The basal ganglia is a set of nuclei deep within your brain that connects the left and right frontal lobes and lets them talk to each other. Research has shown that basal ganglia that are asymmetrical or smaller in size may indicate a higher incidence of ADHD.

The cerebellum is the part of the brain responsible for balance and motor coordination. Having a smaller cerebellum than normal could explain why some people with undiagnosed ADHD have problems with hand-eye coordination.