August 20, 2016 Brain

Alzheimer’s disease (AD) is an irreversible, progressive disorder in which brain cells (neurons) deteriorate, resulting in the loss of cognitive functions, primarily memory, judgment and reasoning, movement coordination and pattern recognition. In advanced stages of the disease, all memory and mental functioning may be lost. The condition predominantly affects the cerebral cortex and hippocampus, which lose mass and shrink (atrophy) as the disease advances.

Brain Anatomy

The cerebral cortex is an extremely convoluted and complicated structure associated with the “higher” functions of the mind—thought, reasoning, sensation, and motion. Each hemisphere of the cerebral cortex contains areas that control certain types of activity. These areas are referred to as the frontal lobe, parietal lobe, temporal lobe, and occipital lobe.

  • The frontal lobe, located behind the forehead, is involved with controlling responses to input from the rest of the central nervous system (brain and spinal cord). It is responsible for voluntary movement, emotion, planning and execution of behavior, intellect, memory, speech, and writing.
  • The parietal lobe, located above the ear, receives and interprets sensations of pain pressure, temperature, touch, size, shape, and body part awareness.
  • The temporal lobe, located behind the ear, is involved in understanding sounds and spoken words, as well as emotion and memory.
  • The occipital lobe, located at the back of the head, is involved in understanding visual images and the meaning of the written word.

The hippocampus plays a crucial role in learning and in processing various forms of information as long-term memory. Damage to the hippocampus produces global amnesia.

Plaques and Tangles

The two most significant physical findings in the cells of brains affected by Alzheimer’s disease are neuritic plaques and neurofibrillary tangles. Another significant factor in AD is the greatly reduced presence of acetylcholine in the cerebral cortex. Acetylcholine is necessary for cognitive function.

While some neuritic plaques, or patches, are commonly found in brains of elderly people, they appear in excessive numbers in the cerebral cortex of Alzheimer’s disease patients. A protein called beta amyloid occupies the center of these plaques. Surrounding the protein are fragments of deteriorating neurons, especially those that produce acetylcholine (ACh), a neurotransmitter essential for processing memory and learning. Neurotransmitters are chemicals that transport information or signals between neurons. Neurofibrillary tangles (NFTs) are twisted remnants of a protein called tau, which is found inside brain cells and is essential for maintaining proper cell structure and function. An abnormality in the tau protein disrupts normal cell activity.

Incidence and Prevalence of Alzheimer’s Disease

According to the Alzheimer’s Association, about 5.2 million people in the United States suffer from Alzheimer’s disease—and two-thirds of those affected are women. The Association reports that about 3.2 million American women and 1.8 million American men over the age of 60 have Alzheimer’s. Approximately 10 percent of all people over the age of 65 and as many as 50 percent of those over the age of 85 are diagnosed with the condition, which is the sixth leading cause for death in the United States.


August 20, 2016 Brain

Amyotrophic lateral sclerosis (ALS), also called Lou Gehrig’s disease, is a progressive neuromuscular disease that weakens and eventually destroys motor neurons (components of the nervous system that connect the brain with the skeletal muscles).

Upper motor neurons are located in the cerebral cortex of the brain and conduct impulses from the motor cortex to nerves in the brain or the spinal cord. Lower motor neurons are peripheral neurons that originate in the spinal cord and conduct impulses to the skeletal muscles. Skeletal muscles are involved with voluntary movements, such as walking and talking. The lower motor neurons transmit the command to move from the brain to the skeletal muscles, which respond by contracting.

A person with ALS usually presents with problems in dexterity or gait resulting from muscle weakness, or with difficulty speaking or swallowing. Sphincter control, sensory function, intellectual ability, and skin integrity are preserved. Patients become paralyzed and often require ventilation and surgery to provide a new opening in the stomach (gastrostomy). Loss of respiratory function is ultimately the cause of death for people who have ALS.

Incidence and Prevalence of ALS:

Approximately 30,000 patients in the United States currently have ALS. The disease has no racial, socioeconomic, or ethnic boundaries. The life expectancy of ALS patients usually ranges from about 3 to 5 years after diagnosis. ALS is most commonly diagnosed in middle age and affects men more often than women.


August 20, 2016 Brain

Attention-deficit hyperactivity disorder (ADHD) is a psychiatric disorder and, more specifically, a chronic neurobehavioral syndrome. ADHD manifests as inattention, impulsivity, and hyperactivity. The term attention-deficit disorder (ADD) refers to the condition without hyperactivity.

People with ADHD tend to overlook details and to miss information. Because of attention deficit, people with ADHD become averse to tasks that require concentration, decisiveness, and organizational skills and may avoid situations where they are expected to perform or to take responsibility for their effort.

Incidence and Prevalence of ADHD:

According to the Centers for Disease Control and Prevention (CDC), 6.4 million people between the ages of 4 and 17—11 percent of the population—in the United States were diagnosed with ADHD as of 2011. The CDC reports that 7.8 percent had an ADHD in 2003, 9.5 percent in 2007, and 11 percent in 2011—indicating about a 5 percent increase in each of those years.

The average age of diagnosis is 7 years. It’s estimated that about 2–4 percent of adults in the United States are affected. The occurrence of ADHD is reported worldwide; statistical variations may be due to cultural perceptions of behavior.

Most studies show that in children with ADHD, boys are affected approximately five times more often than girls. Other studies suggest that the condition may not be diagnosed as often in girls because girls with ADHD present their symptoms differently.

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