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What Is Autism? 3 ASD have more synapses than people without ASD. That is, autistic people seem to have brains that remain at a stage of development before the con- solidation of synapses. It may help to think of the brain and its neurons as a system of con- nected wires that carry electricity. The analogy is apt because neurons carry electrochemical charges. The wires must conduct this electricity in an orderly way for the system to work well. The neurons of the brain of a person with ASD, however, appear to misfire or to fire inefficiently to some degree, impairing the normal functioning of the brain. These misfirings appear to occur in the regions of the brain known as the corpus callosum, the amygdala, and the cerebellum. These areas perform important func- tions. The corpus callosum may be envisioned as a bundle of fibers that connects the two hemispheres of the brain. Consequently it facilitates communication between the two halves. The amygdala, deep within the brain’s temporal lobes, is the center of emotions. Fear, aggression, and pleasure all seem to originate here. At the back of the skull, the cerebellum coordinates the timing, sequence, and rate of muscle contractions. Related to the CNS is the neuroendocrine system, which ASD may also harm. The neuroendocrine system includes a complex group of organs, among them the pineal gland, the pituitary gland, the pancreas, the ova- ries in women or the testes in men, the thyroid gland, the parathyroid gland, the hypothalamus, and the adrenal glands. Glands produce chemi- cals known as hormones that regulate certain areas and processes in the body. In the neuroendocrine system, hormones regulate appetite, metabo- lism, reproduction, osmolarity (the concentration of chemicals in the liq- uid inside a cell), and blood pressure. ASD may harm the neuroendocrine system in several ways. Prominent among these problems is the over or under stimulation of the body’s glands, causing excess or shortage of a hor- mone or hormones. For example, children tend to experience an increase in the (not anabolic) steroid hormone known as cortisol in the morning, but ASD children often do not experience this change. Because cortisol readies the body for activity it is typically high in the morning to give the body a jolt of energy. ASD may also afflict the immune system. The immune system is a group of cells that patrol the body to guard against infection. When these cells detect the presence of a foreign particle, like a bacterium, fungus, or virus, they attack it in hopes of eliminating the invader. In autistic people, the immune system does not always work optimally. In such cases, the immune system may mistake other parts of the body for foreign invaders and attack them instead. For example, in autistic people the immune system may attack the brain, causing the brain to swell as a result. The immune system is also important because it helps the brain develop early in life. Because of the immune system’s role in development, the brain may not mature