Speech agnosia
Speech agnosia, or auditory verbal agnosia, refers to "an inability to comprehend spoken words despite intact hearing, speech production and reading ability". Patients report that they hear sounds being produced, but that the sounds are fundamentally unrecognizable or untranslatable. EXAMINER: What did you eat for breakfast? PATIENT: Breakfast, breakfast, it sounds familiar but it doesnt speak to me. (Obler & Gjerlow 1999:45)Despite an inability to process what the speaker is saying, some patients have been reported to recognize certain characteristic information about the speakers voice (such as being a man or woman). Causes
Agnosia can result from strokes, dementia, or other neurological disorders. It may also be trauma-induced by a head injury, brain infection, or hereditary. Additionally, some forms of agnosia may be the result of developmental disorders. Damage causing agnosia usually occurs in either the occipital or parietal lobes of the brain. Although one modality may be affected, cognitive abilities in other areas are preserved.Patients who experience dramatic recovery from blindness experience significant to total agnosia.The effect of damage to the superior temporal sulcus is consistent with several types of neurolinguistic deficiencies, and some contend that agnosia is one of them. The superior temporal sulcus is vital for speech comprehension because the region is highly involved with the lexical interface. According to the 1985 TRACE II Model, the lexical interface associates sound waves (phonemes) with morphological features to produce meaningful words. This association process is accomplished by lateral inhibition/excitement of certain words within an individuals lexicon (vocabulary).
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 Wernickes 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. References
External links

Types and brain areas
Total Recall: Memory Requires More than the Sum of Its Parts Scientific American (accessdate 2007-06-05)