Norman Geschwind proposed that damage to this bundle caused conduction aphasia; the characteristic deficits in auditory repetition were due to failed transmission of information between the two language centers.
32.
Other types of disconnection syndrome include conduction aphasia ( lesion of the association tract connecting Broca s area and Wernicke s ), agnosia, apraxia, pure alexia, etc.
33.
Conduction aphasia affects a subject's ability to reproduce speech ( typically by repetition ), though it has no influence on the subject's ability to comprehend spoken language.
34.
Although disorders such as expressive aphasia, conduction aphasia, and dysarthria involve similar symptoms as apraxia of speech, the disorders must be distinguished in order to correctly treat the patients.
35.
Traditionally, it has been believed that conduction aphasia was the result of a lesion in the arcuate fasciculus, a deep, white matter bundle connecting the posterior temporoparietal junction with the frontal cortex.
36.
Furthermore, there are reports of patients with severe disruption of the arcuate fasciculus who show no symptoms of conduction aphasia ( although it is plausible that the contralateral hemisphere facilitated repetition in these cases ).
37.
Conduction aphasia has been more specifically related to damage of the arcuate fasciculus, which is vital for both speech and language comprehension, as the arcuate fasiculus makes up the connection between Broca and Wernicke's areas.
38.
Symptoms of conduction aphasia, as with other aphasias, can be transient, lasting only several hours or a few days . As aphasias and other language disorders are frequently due to stroke, their symptoms can change and evolve over time, or simply disappear.
39.
The classical explanation for conduction aphasia is that of a disconnection between the brain areas responsible for speech comprehension ( Wernicke's area ) and speech production ( Broca's area ), due specifically to damage to the arcuate fasciculus, a deep white matter tract.
40.
This explains why conduction aphasiacs have particular difficulty with low-frequency words which requires a more hands-on process for speech production . " Functionally, conduction aphasia has been characterized as a deficit in the ability to encode phonological information for production, " namely because of a disruption in the motor-auditory interface.
