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OBJECTIVES

OBJECTIVES

After studying this chapter, you should be able to:

  • Describe the role of brain imaging techniques in identifying normal brain function and changes caused by brain damage.

  • List the common causes, symptoms, and methods to assess traumatic brain injury (TBI).

  • Describe the various forms of memory and identify the parts of the brain involved in memory processing and storage.

  • Define synaptic plasticity, long-term potentiation (LTP), long-term depression (LTD), habituation, and sensitization, and explain their roles in learning and memory.

  • Identify the abnormalities of brain structure and function that are characteristic of Alzheimer disease.

  • Define the terms categorical hemisphere and representational hemisphere and summarize the differences between them.

  • Identify the cortical areas important for language and their interconnections.

  • Summarize the differences between fluent and nonfluent aphasia and explain each type on the basis of its pathophysiology.

INTRODUCTION

The understanding of brain function in humans has been revolutionized by the development and widespread availability of positron emission tomographic (PET), functional magnetic resonance imaging (fMRI), computed tomography (CT) scanning, and other imaging and diagnostic techniques. CT scans provide a high-resolution 3-dimensional image of the brain; it is useful for examining damage to the skull and detecting acute subarachnoid hemorrhage. PET imaging can measure local glucose metabolism, blood flow, and oxygen; fMRI can measure local amounts of oxygenated blood. PET and fMRI provide an index of the level of the activity in various parts of the brain in healthy humans and in those with pathologies or brain injuries (see Clinical Box 15–1). They are used to study not only simple responses but also complex aspects of learning, memory, and perception. Different portions of the cortex are activated when a person is hearing, seeing, speaking, or generating words. Figure 15–1 shows examples of the use of imaging to compare the functions of the cerebral cortex in processing words in a male versus a female subject.

FIGURE 15–1

Comparison of the images of the active areas of the brain in a man (left) and a woman (right) during a language-based activity. Women use both sides of their brain whereas men use only a single side. This difference may reflect different strategies used for language processing. (Used with permission of Shaywitz et al, 1995. NMR Research/Yale Medical School.)

CLINICAL BOX 15–1 Traumatic Brain Injury

Traumatic brain injury (TBI) is defined as a nondegenerative, noncongenital insult to the brain due to an excessive mechanical force or penetrating injury to the head. It can lead to a permanent or temporary impairment of cognitive, physical, emotional, and behavioral functions, and it can be associated with a diminished or altered state of consciousness. TBI is one of the leading causes of death or disability worldwide. According to the Centers for Disease Control and Prevention, each year at least 1.5 million individuals in the United States sustain ...

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