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APHASIA, APRAXIA AND AGNOSIA |
Aphasia is an acquired impairment in the
ability to spontaneously produce, understand, and/or repeat speech. Defects in
the ability to read and write also constitute aphasia. Deficits can be
identified in the language syntax, semantics, and phonology. There are several
classic types of aphasia (see learning objective on
Broca's, Wernicke's and Conduction aphasias).
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Apraxia is the inability to perform a motor
activity on command in the presence of intact motor and sensory systems,
comprehension, and cooperation. There are several types of apraxia:
Motor Apraxia. Motor apraxia is a
disturbance of voluntary movement in which one cannot use objects for the
purposes that they were designed for. However, the affected individual still
knows what the object should be used for. So for example, a person with motor
apraxia knows that a hammer is used to hammer a nail, but cannot use the hammer
for that purpose.
Ideomotor Apraxia. Ideomotor apraxia is a
disturbance of voluntary movement in which a person cannot translate an idea
into movement. People with ideomotor apraxia can still perform automatic
movements, such as using scissors. However, they cannot perform such movements
upon request. They also cannot copy movements or make gestures.
Ideational Apraxia. Ideational apraxia is a disturbance of voluntary
movement in which a person misuses objects because he/she has difficulty
identifying the concept or purpose behind the objects. For example, it would be
difficult to use a hammer if one could not identify what the purpose of a hammer
was. It is important to note that motor movement is not lost in ideational
apraxia. However, the person's movements appear confused because he/she cannot
form a plan on how to sequence those movements when using an object.
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Agnosia is an impairment of the ability to
recognize, or comprehend the meaning of various sensory stimuli, not
attributable to disorders of the primary receptors or general intellect.
Agnosias are receptive defects.
Apperceptive Agnosia. This condition
involves poor perception of form and the complaint of poor vision despite good
acuity, intact perception of movement and colors. Distinguishing features of
this condition are the inability to draw objects, copy figures, or distinguish
different shapes. The lesion is most often localizable to the calcarine cortex.
Associative Agnosia. Patients with this condition cannot recognize
objects through vision alone. They are unable to name, describe, or mimic the
use of objects. Patients deny visual complaints and are able to draw, copy, and
distinguish shapes. The lesion is usually bilateral and involves the inferior
temporal occipital lobes including the visual association cortex. |
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