Frontal lobe disinhibition, Rett syndrome and attention deficit hyperactivity disorder.

Motor cortex hyperexcitability in Rett Syndrome (RS) has been ascribed to the failure of an inhibiting system arising from the frontal lobes, a system needed in childhood and early adolescence. It is also presumed that, on a virtually dysfunctional (nonstructural) basis, motor cortex hyperexcitability in ADHD is also due to insufficient frontal lobe inhibition ("lazy frontal lobe"). A series of schematic illustrations is added for the sake of easier comprehension of the presented concept.