How Have Our Views of the Brain Evolved?
Though it has been understood since ancient times that there is a relationship between the mind and the brain, our understanding of how the structures of the brain control the mind has evolved over time. One critical debate centered on the idea of equipotentiality versus localization of function. Do all parts of the brain contributing equally to mental function, or can mental functions be mapped to specific regions of the brain?

Though the idea of localization of function was carried to ridiculous extremes by the pseudoscience of phrenology, advocates of this idea were on the right track. It is now known that the brain's surface is a patchwork of many specialized areas that control rudimentary components of perception, behavior, and mental life. Throughout history our understanding of brain function has been greatly aided by the observation of patients with head injury. For instance, Paul Broca's investigation of a patient who could say only the word tan provided evidence that the left frontal region of the brain (Broca's area) played a crucial role in speech production, and behavior changes exhibited by Phineas Gage provided the basis for modern theories that the prefrontal cortex governs personality and self-control. More recently, functional brain imaging techniques allow us to generate maps of the healthy human brain in action. These techniques include electroencephalography (EEG) and magnetoencephalography (MEG), which both provide good temporal resolution of mental activity, and positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), which both provide good special resolution of mental events.

What are the Basic Brain Structures and Their Functions?
After providing you with an appreciation for the specialized nature of the human brain, the authors lead you through a tour of the basic brain structures that make up the central nervous system and identify the functions controlled by each structure. Though this material may seem overwhelming at first, it is helpful to remember that functioning becomes increasingly complex as you progress from the spinal cord upward through the structures of the hindbrain, midbrain, forebrain, and cerebral cortex. After studying this section you should be able to identify the location and the functions controlled by each of the following structures and substructures:

Memorizing the numerous structures in the brain can be a daunting task. Being able to visualize where in the brain these structures are located will help your study of this material. In learning the function of these brain structures, think about what sort of impairments would result from damage to the various structures.

How is the Brain Divided?
The split-brain condition has provided researchers with a wealth of information about the different roles the two cerebral hemispheres play in behavior. For most individuals, the left hemisphere is responsible for language abilities but is incapable of performing spatial tasks—a right hemisphere skill. The left hemisphere has a tendency to try to make sense out of the world, a tendency known as the interpreter. This interpreter affects how we understand and remember our world, creating a comprehensible story out of our experiences and paying attention to information that is consistent and rejecting information that is inconsistent.

How Does the Brain Change?
The brain changes throughout development and as a result of experience, a property known as plasticity. This plasticity allows the brain to recover some function after injury, though typically brain plasticity decreases with age. Changes in neuronal connections occur as a result of experience. This is the basis of learning. Neurons that fire together strengthen their connections with one another, increasing the likelihood that they will fire together in the future, a process known as Hebbian learning.