How Can Damage of the Brain in Each of the Following Structures Affect One’s Mental Processes and Behavior?
Research has demonstrated the importance of understanding brain disorders as it affects one’s mental processes and behavior. In particular, studies revealed that brain damage may occur due to a wide range of causes, including illnesses, head injuries, complex chemical imbalances, bacterial diseases, and changes associated with aging. These broad categories of influence can lead to very specific or very generalized affective disorders depending on the region damaged.
The medulla oblongata, usually just called the medulla, contains a number of vital centers for regulating heartbeat, breathing, and blood pressure. It also contains the reflex centers for vomiting, coughing, sneezing, hiccoughing, and swallowing (Mader 134). Destruction of the medulla causes instant death (Carlson 302).
The reticular formation receives sensory information by means of various pathways and projects axons to the cerebral cortex, thalamus, and spinal cord. It plays a role in sleep and arousal, attention, muscle tonus, movement, and various vital reflexes (Mader 137). Damage to reticular formation interferes with normal arousal and produces coma by interfering with this mechanism (Carlson 304).
The cerebellum receives visual, auditory, vestibular, and somatosensory information, and it also receives information about individual muscle movements being directed by the brain. The cerebellum integrates this information and modifies the motor outflow, exerting a coordinating and smooth effect on the movements (Mader 217). Damage to the cerebellum impairs standing, walking, or performance of coordinated movements. It also results in jerky, poorly coordinate, exaggerated movements; extensive cerebellar damage makes it impossible even to stand (Carlson 267).
The hypothalamus controls the autonomic nervous system and the endocrine system and organizes the four F’s of survival: fighting, feeding, fleeing, and mating. Damage to the hypothalamus is quickly fatal as the homeostasis of body temperature, blood chemistry, and etc. goes out of control (Mader 98). An injury or disturbance to the lateral hypothalamus can cause anorexia. If the ventromedial portion has a lesion or is destroyed then an individual has a tendency to become morbidly obese. Many sleep dysfunctions can come about with the damage of hypothalamus. One in particular is called the Prader-Willi Syndrome. Certain behaviors can also be affected like emotions, mating/sexual behavior, waste excretion, and the senses of pleasure or aversion (Carlson 344-45).
The amygdala plays a special role in physiological and behavioral reactions to object and situations that have special biological significance, such as those that warn of pain or other unpleasant consequences or signify the presence of food, water, salt, potential mates or rivals, or infants in need of care (Mader 98). Damage to amygdala impairs both the acquisition and expression of Pavlovian fear conditioning, a form of classical conditioning of emotional responses. It interferes with the effect of emotions on memory. Normally, when people encounter events that produce a strong emotional response, they are more likely to remember these events. However, a patient with amygdala damage showed no such increase in memory (Carlson 286).
The hippocampus is essential for the formation of long-term memories. In Alzheimer’s disease, the hippocampus is one of the first regions of the brain to suffer damage (Mader 350). Damage to the hippocampus usually results in profound difficulties in forming new memories (anterograde amnesia), and normally also affects access to memories prior to the damage (retrograde amnesia). Many people with damage to the hippocampus can remember the distant past but cannot form new memories. They can, however, learn new skills (Carlson 139).
Several diagnostic methods give images of the brain without invading the skull such as magnetic resonance imaging (MRI), computed tomography (CT), functional magnetic resonance imaging (FMRI), positron emission tomography (PET), and single photon emission computed tomography (SPECT). Two or more methods may be used to complement each other, together providing a more complete picture than would be possible by one method alone (Toga).
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