History
Some of the first ideas about agnosia came from Wernicke who created theories about receptive aphasia in 1874. He noted that individuals with receptive aphasia did not possess the ability to understand speech or repeat words. He believed that receptive aphasia was due to lesions of the posterior third of the left superior temporal gyrus. Due to these lesions, Wernicke believed that individuals with receptive aphasia had a limited deafness for certain sounds and frequencies in speech.
After Wernicke, came Kussmaul in 1877 who attempted to explain why Auditory verbal agnosia, also known as word deafness, occurs. Contrary to Wernicke's explanations, Kussmaul believed Auditory verbal agnosia was the result of major destruction to the first left temporal gyrus. Kussmaul also posited about the origins of Alexia (acquired dyslexia) also known as word blindness. He believed that word blindness was the result of lesions to the left angular and supramarginal gyri.
Heinrich Lissauer shared his ideas about agnosia after Wernicke and Kussmaul. In 1890, he theorized that there were two ways in which object recognition impairment could occur. One way in which impairment could occur was if there was damage to early perceptual processing or if there was damage to the actual object representation. If the actual object representation was damaged, this would not allow the object to be stored in visual memory, and therefore the individual would not be able to recognize the object. During the time of Wernicke, Kussmaul and Lissauer there was little known about the cerebral cortex. Today with new neuroimaging techniques we have been able to expand our knowledge on agnosia greatly.
Read more about this topic: Associative Agnosia
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