The Brain
Objectives:
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Identify and describe several techniques for studying the brain.
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Describe the functions of the brainstem, thalamus, cerebellum, and limbic system.
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Identify the four lobes of the cerebral cortex and describe the sensory and motor functions of the cortex.
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Discuss the importance of association areas, and describe how damage to several different cortical areas can impair language functioning.
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Discuss the capacity of the brain to reorganize following injury or illness.
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Describe research on the split brain, and discuss what it reveals regarding normal brain functioning.
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Discuss the relationships among brain organization, right-and left-handedness, and physical health.
Key Vocabulary:
Lesion – tissue destruction. A brain lesion is a naturally or experimentally caused destruction of brain tissue.
Electroencephalogram (EEG)– an amplified recording of the waves of electrical activity that sweep across the brain’s surface. These waves are measured by electrodes placed on the scalp.
Computer tomography scan (CAT)– a series of x-ray photographs taken from different angles and combined by computer into a composite representation of a slice through the body. Also called a CAT scan.
Positron emission tomograph (PET)– a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task.
Magnetic resonance imaging (MRI)– a technique that uses magnetic fields and radio waves to produce computer generated images to distinguish among different types of soft tissue. This allows us to see structures within the brain.
Brainstem– the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions.
Medulla– the base of the brainstem; controls heartbeat and breathing.
Reticular formation– a nerve network in the brainstem that plays an important role in controlling arousal.
Thalamus– the brain’s sensory switchboard, located at the top of the brainstem; it directs messages to sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla.
Cerebellum– the “little brain” attached to the rear of the brainstem; helps coordinate voluntary movement and balance.
Limbic system– a doughnut shaped system of neural structures at the border of the brainstem and cerebral hemispheres; associated with emotions such as fear and aggression and drives such as those for food and sex. Includes the hippocampus, amygdala, and hypothalamus.
Amygdala– two almond shaped neural clusters that are components of the limbic system and are linked to emotion (fear and agression).
Hypothalamus– a neural structure lying below the thalamus; it directs several maintenance activities such as eating, drinking, and body temperature. It also helps govern the endocrine system via the pituitary gland, and is linked to emotion.
Cerebral cortex– the intricate fabric of interconnected neural cells that covers the cerebral hemispheres; the body’s ultimate control and information-processing center.
Glial cells– cells in the nervous system that are not neurons but that support, nourish, and protect neurons.
Frontal lobes– the portion of the cerebral cortex lying just behind the forehead; involved in speaking and muscle movements and in making plans and judgments.
Parietal lobes– the portion of the cerebral cortex lying at the top of the head and toward the rear; includes the sensory cortex.
Occipital lobes– the portion of the cerebral cortex lying in the back of the head; includes the visual areas, which we receive visual information from the opposite visual field.
Temporal lobes– the portion of the cerebral cortex lying roughly above the ears; includes the auditory areas, each of which receives auditory information primarily from the opposite ear.
Motor cortex– an area at the rear of the frontal lobes that controls voluntary movements.
Sensory cortex– the area at the front of the parietal lobes that registers and processes body sensations.
Association areas– areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking.
Aphasia– impairment of language usually caused by left hemisphere damage either to Broca’s area or to Wernicke’s area.
Broca’s area– an area of the frontal lobe, usually in the left hemisphere, that directs the muscle movements involved in speech.
Wernicke’s area– a brain area involved in language comprehension and expression. Usually in the left temporal lobe.
Plasticity– the brains capacity for modification, as evident in brain reorganization following damage and in experiments on the effects of experience on brain development.
Corpus callosum– the large band of neural fibers connecting the two brain hemispheres and carrying the messages between them.
Split brain– a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers between them.