Dyslexia

Dyslexia means dys = difficulty; lexis = words.

Dyslexia is an impairment of the brain's ability to translate image received from the eyes into understandable language. The condition is unrelated to basic intellectual capacity, but it cause a mysterious difficulty in processing words and symbols. 

Apparently, some peculiarity in the brain's organizational pattern distort the ability to read, write and count. Letters in words seem transposed, revered or upside down - dog becomes god or bog; b changes identity with d; a sign saying "OIL" invert into "710". 

Frequently, dyslectics reread portions of paragraphs, skip words and change the order of letters in a word. Many dyslectics cannot orient themselves in the three dimensions of space and may show bodily awkwardness. 

The exact cause of dyslexia is unknown, since it is unaccompanied by outward scars of detectable neurological damage and its symptoms vary. It occurs about three times as often among boys as among girls. It has been variously attributed to defectives vision, brain damage, abnormal brain development, lead in the air, physical trauma or oxygen deprivation during birth. 

Positron emission tomography (PET) scans provide some information about dyslexia. For example, PET scans have demonstrated that in persons with dyslexia the left side of the brain is more active than the right, the language region is less active than normal, and visual discrimination region is more active.