Aphasic acalculia is seen in patients with various types of aphasia. Broca's aphasics have defects derived from linguistic changes, which are numeric-symbolic in nature. Wernicke aphasics have altered visual-spatial processes which are a significant factor in the calculation problems. Conduction aphasics will also be examined below.
These three types of aphasia are not the only types to have calculation disturbances accompany them. In extrasylvian motor aphasia there are problems with numerical sequencing while in extrasylvian sensory aphasia there are considerable calculation deficits seen.
Broca's Area (www.answers.com)
Since the defects in calculation seen in Broca's aphasics are linguistic in nature, these individuals often have impairments in the syntax of calculation. They have problems morphologically when reading numbers (eg, 15 is read as 50) and they have a hard time counting numbers backwards. Also, these individuals will be likely to omit words when converting numbers in their digit form to the word form or the inverse of this task (eg, "110" to "one hundred ten", this is known as a transcoding task) (Rosselli and Ardila, 1990).
Wernicke's Area (www.thebestlinks.com)
These individuals have semantic errors while reading and writing numbers (Deloche and Seron, 1982). Frequently there is incorrect word production in oral reading of numbers. Also, there is a verbal memory problem when solving mathematical problems that results in trouble retaining elements of the problem. In addition, defects in lexicalization (eg, 125 written as 102005) and decomposition (eg, 125 written as 1 25) errors are common.
Conduction aphasia is an uncommon form of aphasia and believed to be caused by a disruption of the fiber pathways that connect Broca's area and Wernicke's area. This fiber pathway is known as the arcuate fasciculus and is essential for language.
The arcuate fasciculus. (http://www.ruf.rice.edu/~lngbrain/)
In conduction aphasics it is possible that both written and oral forms of calculation could be impaired. Solving basic mathematical problems, sequencing of numbers and transcoding tasks all are difficult to complete. Some also feel that Conduction aphasia is associated with primary acalculia (anarithmetia). This is due to the left parietal lobe damage in conduction aphasics, which is close to the angular gyrus, the area suspected for anarithmetia.