The Human Brain Structure and Function

Brain Structure and Function

• The brain is the most complex organ of the body, consisting of approximately 100 billion nerve cells (neurons) and billions of fibers that interconnect them.
• The surface of the brain is the cortex, also known as "gray matter", comprising billions of neurons that serve as the decision-making organ of the body.
• The cortex receives messages from all sensory organs, initiates voluntary and involuntary actions, and stores memories.

Cerebral Hemispheres

• The brain is composed of two cerebral hemispheres, one on the right and one on the left, connected by the corpus callosum, a network of over 200 million fibers.
• The corpus callosum enables the two hemispheres to communicate with each other, preventing them from operating independently.

Brain Function and Laterality

• The left hemisphere controls the right side of the body, while the right hemisphere controls the left side.
• Contralateral brain function refers to the fact that sensory information from the right side of the body is received by the left hemisphere, and sensory input from the left side is received by the right hemisphere.

The Localization of Linguistic Abilities

• In the 19th century, Franz Joseph Gall proposed the theory of localization, which states that different human cognitive abilities and behaviors are localized in specific parts of the brain.
• Gall's theory was based on the idea that the brain is not a uniform mass, and that linguistic and other cognitive capacities are functions of localized brain areas.

Phrenology

• Gall also proposed the pseudoscientific theory of "organology", later known as phrenology, which involves determining personality traits, intellectual capacities, and other matters by examining the "bumps" on the skull.
• Johann Spurzheim, a disciple of Gall's, introduced phrenology to America and constructed elaborate maps and skull models.
• One such model, shown in Figure I.2, locates language directly under the eye.

Legacy of Gall's Work

• Although phrenology has been discarded as a scientific theory, Gall's view that the brain is not a uniform mass and that linguistic and other cognitive capacities are functions of localized brain areas has been upheld by scientific investigation of brain disorders.
• Over the past two decades, numerous studies using sophisticated technologies have supported Gall's theory of localization.