Identity And Universals: A Conceptualist Approach to Logical, Metaphysical, and Epistemological Problems of Contemporary Identity Theory
Appendix B, Brain Damage and Neurological Disorders
by Carolyn Ray
Date: 11 Nov 98
Copyright: Carolyn Ray
Alzheimer's Disease: Caused by scattered or concentrated degeneration of nerve-cells in the brain. Demented persons tend to live for the present moment, which can for them some moment they remember from the distant past. The victim has difficulty in both comprehension and expression, and fails to recognize things. He can handle objects with no problems, but forgets what his goal was while in the middle of performing his task. (Williams, Moyra, 'Dementia')
Amnesia: Classical pure amnesia results from damage to the limbic system, involving the temporal lobes, hippocampus, mammillary bodies, caused by Korsakoff's syndrome (alcohol-related--see reference below), stroke, tumor, coal gas poisoning. Unable to say what they have had for breakfast, for example; no idea where they are or how long they have been there; unable to recognize in the afternoon someone they have just spent the day with; queries for current information are answered with information from years before; difficulty learning lists of words, or non-verbal materials. Unlike people suffering from traumatic amnesia, these people do not recover. E.g., Jimmy G.) (Baddeley, 'Amnesia'). Other parts of the brain do not "take over" for the damaged parts.
Anomalous Experiences of The Body: Results from damage to the parietal lobes, where knowledge of the body schema--implicit knowledge about the spatial properties of one's body--is processed. This schema, stored or processed in the lobes, is responsible for phantom limbs. The victim believes that one of his limbs does not really belong to him, despite the fact that it is fully functional, or he may think it is distorted or not attached. (Howard, 'Spatial Coordination of the Senses')
Aphasia: Results from damage to the left cerebral hemisphere. Severity is a matter of degree, ranging from inability to name objects (especially common ones), to almost complete loss of ability to comprehend language or speak. Recovery from such damage occurs only in infancy or childhood. Non-fluent aphasiacs find that words evade them, though they can recognize objects; caused by damage to the anterior part of the left hemisphere. Fluent aphasiacs "use" (or perhaps we should say, "mention") words fluently but meaninglessly, producing incoherent strings of words, and seem unaware of the problem; caused by damage to the posterior part of the left hemisphere and possibly damage to the right. Much speech can be recovered, especially in younger victims. (Williams, Moyra, 'Aphasia')
Apraxia: Occurs in humans only. The inability to make purposeful skilled movements. Occurs following damage to left hemisphere. Ideomotor apraxia involves impairment of the execution of simple or complex movements of the oro-facial musculature and/or limbs. Movements are distorted. Execution is impaired only when they are performed out of their "natural context." Victims tend to repeat movements and speech inappropriately. Ideational apraxia involves impairment of execution of sequences of action to attain a goal, such as preparing or eating a meal. (Poeck, 'Apraxia')
Ataxia: Proprioceptive ataxia results from an impaired sense of joint perception: lack of coordination between muscles that causes unsteadiness in posture and movement, affects eye movement and speech. Motor ataxia results from cerebellar disorders. (Gregory, 'Ataxia')
Hemianopsia: Damage to visual pathways in damaged hemisphere results in failure to see objects on one side; tends to walk into door frames, etc. (Langton-Hewer, 'Stroke')
Korsakoff's Syndrome: (Also, 'Korsakov's') Caused by one or all of the following: damage to floor of third ventricle, hippocampus, mammillary bodies; atrophy of the frontal lobes, dilatations of the cerebral ventricles; the area of damage can be quite miniscule. "Presented with an object he has been shown a few minutes before, he tends to respond to it as not identical or as in some manner changed" (Davis, p. 414). Answers questions about recent activities by describing events from his distant past, and does not seem to notice the discrepancy. (Davis, 'Korsakoff's Syndrome')
Muteness and Language Comprehension Disturbances: Caused by damage to the left hemisphere. These are conditions, respectively, in which the victim loses speech or language comprehension. If the right hemisphere is shown a picture of some object, the victim can point to or pick up an example, but cannot say the name of the object. Cannot classify objects merely according to size, form, or color. (Trevarthen, 'Split Brain and the Mind')
Prosopagnosia: Caused by damage to the posterior right hemisphere. A condition in which faces are not recognized. The left hemisphere must attempt to compensate by creating and memorizing a check-list that can be consulted in social situations (note that the specific function of the posterior right hemisphere is not duplicated; rather a much less sophisticated one is substituted). Success with the check-list is minimal, for obvious reasons: to be accurate, the list must be longer than is retrievable, and the left hemisphere is in the first place bad at recognizing the shapes necessary to describe and file in the list. (Langton-Hewer, 'Stroke')
Visuo-spatial Disorders: Damage to right hemisphere produces disorders of orientation and perception. Victim may neglect or deny the existence of left limbs or left body; inability to draw symmetrical objects, to dress. (Langton-Hewer, 'Stroke)
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