Attention-deficit hyperactivity disorder (ADHD) is a condition characterized by an inability to control one’s attention span so as to effectively complete one activity or cognitive process before proceeding to another. This leads to impulsive decision-making and actions, and typically a hyperkinetic mode of life.
ADHD is a disorder which primarily originates in and affects the brain in different ways. The brain controls and regulates all physiological activities, assigning tasks to various areas within itself. Thus it can execute the following functions; namely, receiving sensory information, initiation, performance and coordination of voluntary and involuntary movements, regulate moods and emotions, and behavioral control, among others. Information processing and sharing across vast neural networks is thus an essential part of normal brain functioning. This is achieved by neurotransmitters which transmit nervous stimuli across synapses to other neurons.
ADHD is associated with abnormally low levels of the neurotransmitters transmitting between the prefrontal cortical area and the basal ganglia i.e., dopamine and noradrenaline. Dopamine is closely associated with reward centers in the brain, and also interacts with other potent neurotransmitters to regulate mood. Low dopamine levels thus drive the individual to seek the reward feeling by other means.
Serotonin transporter gene polymorphisms are also known to be associated with different modes of response to treatment. In addition, glutamate levels may be lower in adults with ADHD, which could be responsible for the neurotransmitter abnormalities. This causes dysfunctional neural networking in the above parts of the brain.
The prefrontal cortex controls emotional responses, behavior and what is called judgment, which decides on the appropriateness of different actions, and of course, attention to the present task which enables individuals without ADHD to execute routine tasks without deliberate and focused attention to each step of the task. It is the part which plans, initiates and perfects actions as well as executing corrections, averting roadblocks by alternative actions, and enabling concentration on the task at hand. The basal ganglia regulate impulsive behavior so as to prevent unwarranted automatic responses to stimuli.