A GOOD CATCH [ THE NERVOUS SYSTEM ]

When the ball hits the glove, mechanoreceptors in the hand register the arrival as pressure. Those in the ear, attuned to the vibrations of sound waves, record the thwack of ball hitting leather. (And if the leather in the palm is too thin, cell damage in the hand may release noxious chemicals such as prostaglandins, which set off a chemical chain reaction ending with nociceptors initiating pain signals to the brain.) The cortex processes the new sensory stimuli, perceives that the ball has arrived, and sets in motion, with the cerebellum’s help, the voluntary muscle contractions that squeeze the gloved fingers.

Another way to think of the integration of brain functions, in a metaphor of psychiatry professor John J. Ratey’s, is to picture a house. Some functions exist on only one floor-the furnace kicks on automatically in the basement when the thermostat tells it to but others require communication among all the floors. The basement has the brain stem and spinal cord, which automatically oversee reflexes and respiration. The first floor houses basal ganglia and the cerebellum, which oversee the basement and communicate information to the upper floors. The second floor has centers of increasing control over the nervous system such as the motor and premotor cortex. The top floor is home to the prefrontal cortex, decision-maker of the brain. The top floor’s decisions get communicated downward, receiving feedback as they are carried out.

MANUAL DEXTERITY

EVOLUTION HAS selected for the development of eye hand coordination in human beings. As humanity’s ancestors swung from branches, they refined their performance by figuring out how to grasp one limb after another. Later, as they stood on two feet, they freed their hands for manipulating objects. Manual dexterity improved through brain hand feedback, leading to the creation of tools and other developments that aided survival. Today, the hand is so closely integrated to the neural circuitry of the brain that neurologist Richard Restak suggests it is best thought of as an extension of the brain.

His disease was amyotrophic lateral sclerosis. Such was the sudden drama of his situation that the illness claiming his life is sometimes called Lou Gehrig’s disease. This devastating disease gradually destroys motor neurons. As motor nerves lose their ability to send signals that move muscles, the muscles atrophy. Those afflicted lose their ability to speak and swallow, and eventually even to breathe. Researchers hypothesize that the motor neurons are killed by an attack of the sufferer’s own immune system, the production of too much of the neurotransmitter glutamate, or both. In making his farewell to 62,000 fans at Yankee Stadium on July 4, 1939, GEHRIG called himself “the luckiest man on the face of the Earth.” For his performance on the field, as well as his demeanor while faCing a final opponent he could not defeat, GEHRIG is remembered as a “Gibraltar in cleats.”