Assignment: Brain-Centered Explanations

Assignment: Brain-Centered Explanations
Assignment: Brain-Centered Explanations
Permalink:
Assignment: Brain-Centered Explanations of Behavior
For Further Thought: Why Doesn’t Poking the Brain Produce Pain? (continued)
In order to feel pain, special nerve cells called pain receptors are needed. Pain receptors are located throughout the skin, muscles, and bones in the body. When these pain receptors are stimulated, mes- sages about pain are sent to the brain, and pain is experienced. The brain contains no pain receptors. Thus, no anesthesia is required as the surgeon cuts through tissue in the brain.
Aristotle studied all kinds of animals, from tiny rodents to elephants. He observed that the body grows cold when the heart stops beating, which led him to believe that the heart produces the body’s heat. It occurred to Aristotle that a mechanism was needed to cool the incessant heart, and he assigned this function to the brain. In addition, scholars in Aristotle’s time knew that the human voice is produced by air exhaled from the lungs. Aristotle reasoned that the words are supplied by the heart and, therefore, that the words and voice roll out of the chest cavity together.
Aristotle’s cardiocentric view survived into the Middle Ages. As late as the 16th century, medi- cal students and students of anatomy were taught that nerves, like all veins and arteries, origi- nate from the heart. Anatomical dissection studies demonstrated that arteries, veins, and nerves course through the body bundled together in sheaves. Tracing the veins and arteries back to the heart led to the obvious, but erroneous, conclusion that the nerves also come from the heart.
1.2 Brain-Centered Explanations of Behavior
Many ancient Greeks did not agree with Aristotle’s cardiocentric view, however. Encephalocentric explanations, or brain-centered explanations, of behavior came about as a result of dissection studies of human and other animal cadavers (encephalon means “brain” in Greek). Known as the father of medicine, Hippocrates (460–377 BCE) supervised dissections of human bodies on the island of Cos in ancient Greece. These dissections led to the discovery of nerves and nerve function.
Galen (130–200 CE), often called the father of experimental physiology, also disagreed with Aris- totle’s cardiocentric view. He reasoned that, if indeed the function of the brain is to cool the heart, it would be located closer to the heart. His own work indicated that the brain is of paramount importance. In one experiment, Galen cut through the medulla, right above the spinal cord in the brain, and observed that breathing ceased. This led him to conclude that the brain controls respi- ration (Spillane, 1981).
Galen firmly established the brain’s central role in human behavior. Since Galen’s time, over many centuries, scientists studied the anatomy of the brain, cataloguing its many structures, cavities, fissures, and bulges. But descriptions of the brain’s functioning were pure fantasy until the 19th century, when formal study of the brain began.
Controlled experiments involving the brain were rare until the 19th century. Before 1800 most knowledge about the brain came from observations of people who suffered head injuries, such as a kick in the head from a horse or a gunshot wound to the head. It was observed that people who received injuries to the back of the head invariably had visual or motor impairments afterward.
wiL81028_01_c01_001-030.indd 4 7/10/13 12:23 PM