Section 1: Symptoms and Circuits

In this chapter, the hypothetical pathophysiology underlying attention deficit hyperactivity disorder (ADHD) is discussed. Besides providing an overview of the main hypothesis underlying the symptoms of ADHD, such as problems with executive functioning, this chapter will also peruse old and new views on the environmentneurobiology interaction of this disorder. By giving a holistic view of the disorder, it will hopefully become clear that many different treatment options are available for every symptom of ADHD. Section 1 of Chapter 1 will focus on the symptoms of ADHD, and the circuits underlying these symptoms.

The mechanism of action of alpha2A (Figure 1.23) and D1 receptors explains in general why moderate stimulation of both types of receptors (Figure 1.21) is preferred in order to strengthen the signal-to-noise ratio in prefrontal cortical neurons (see Figure 1.25).