Functional MRI shows under activation in areas where they are weaker and over activation in other areas to compensate. Thus there is a failure of the left hemisphere rear brain systems to function properly during reading. There is also greater activation in the lower frondal areas of the brain. This leads to conclusion that neutral systems in frontal regions may compensate for the distruption in the posterior area.
Functional MRI in individuals have shown three areas of left hemisphere to be active while reading.
1. Broca’s area and inferior frontal gyrus
2 . Parieto – temporal area
3 . Occipito – temporal area
The Broca’ s area and inferior frontal gyrus is responsible for a relatively slow process of articulation and word formation.
The parieto-temporal area is responsible for word analysis: It is believed to analyse a word, pull it apart and link its orthography ( letters) to sound.
The occipito temporal area is the express pathway to reading open to the skilled reader. This area reacts almost instantly to all the word as a pattern identifying the word by sight . It helps in identifying written word .
There are thus three neutral pathways for reading, two slower analytical one’s, that are mainly used by the beginning readers and express route, the occipito temporal, relied on by experienced skilled readers.