Study of Attention Deficit/Hyperactivity Disorder Using Transcranial Magnetic Stimulation

Attention deficit/hyperactivity disorder is a condition characterized by a decreased attention span, hyperactivity, and/or impulsiveness inappropriate for a certain age.

Typically, young children have what are known as subtle neurological signs. These are involuntary movements of one part of the body that occur while the child is making a voluntary movement of another part of the body. This is referred to as synkinesis, or overflow movements. These overflow movements disappear during normal development and are usually gone by the age of 10. However, in children with ADHD these overflow movements tend to be more intense and last long after the age of 10. This leads researchers to believe there is an abnormality in the maturation and development of the brain areas associated with motor activity in children with ADHD.

Transcranial Magnetic Stimulation (TMS) is a non-invasive technique that gives information about brain function. It is very useful when studying areas of the nervous system related to motor activity (motor cortex, corticospinal tract, and corpus callosum). A magnetic signal given from a special instrument held close to the patient's head stimulates a small area of the brain that controls a few muscles (for example, the muscles that control one finger). Doctors put electrodes (small pieces of metal taped to areas of the body) over the muscle to measure the electrical activity the muscle produces when it makes a movement. When the magnetic signal activates those muscles the electrodes pick up and record the electrical activity of the movement that the muscles make in response to the magnetic signal.

Researchers will study normal children and those diagnosed with ADHD using TMS to find out if the clinical abnormalities of ADHD are associated with a delay or abnormality in maturation of areas of the nervous system responsible for motor activity (motor cortex and corticospinal tract).