| In word reading, information is processed on a | | | | regards to the ability of dyslexics in picture |
| letter level, in a semantic system and in an | | | | naming and confrontational naming. |
| orthographic system. Written word to speech | | | | A recent study assessed picture retrieval time in |
| articulation may be processed by two routes: a | | | | dyslexic children by determining the time between |
| direct and indirect method. The direct route can | | | | the retina fovea landing on the picture by laser |
| be described as a semantic one. In this system, a | | | | scanning ophthalmoscopy and the beginning of |
| direct access to the semantic system is allowed. | | | | speech articulation. There was a vast range of |
| In the indirect route, features of the letters in a | | | | overlap between dyslexics and non-language |
| word activate the word's letter units in order to | | | | impaired children. The finding of normal picture |
| activate the word's entry to the orthographic | | | | naming, despite severely impaired reading ability in |
| lexicon. This procedure is succeeded by the | | | | dyslexics may lead to the assumption that |
| word's entry to the orthographic lexicon. This | | | | different pathways may be involved in processing |
| route converts a letter string to a phoneme string | | | | letter-mediated information and picture naming. To |
| through grapheme-phoneme conversion. This | | | | further confirm this hypothesis, a recent study in |
| conversion serially assembles letters into | | | | Germany assessed the brain response patterns in |
| phonology. Dyslexia can be caused by any | | | | dyslexic children and normal counterparts to see |
| dysfunction of any of the mentioned components | | | | whether different neural patterns were used to |
| of information processing. | | | | process picture naming and word reading. |
| One of the most controversial issues on the | | | | Magnetoencephalography was used to investigate |
| pathomechanisms of developmental dyslexia is | | | | brain activation during word reading and picture |
| impairment in phonological language processing. | | | | naming tasks. Results show consecutive cortical |
| Several evidences has supported this notion - | | | | activation spreading in various brain areas. |
| studies showing anatomical malformations in | | | | Differences in both groups were seen only during |
| language-associated brain regions (Galaburda et al., | | | | the reading task: a delayed response in the |
| 1985: Dalby et al., 1998), neurobehavioural and | | | | temporal superior and angular gyri at 235-285 |
| neuropsychological studies showing increasing | | | | milliseconds and absence of neural cortical |
| reading difficulties correlating with increasing task | | | | activation in the anterior temporal and inferior |
| demands of phonological processing (Wimmer, | | | | frontal areas at 430-530 milliseconds for dyslexics. |
| 1993; Warnke, 1999) and functional brain imaging | | | | Difficulties in phonological processing were |
| studies describing an abnormal brain activity in the | | | | reflected in the delay of activity and absence of |
| left auditory cortex during reading tasks in | | | | late activity and language related brain regions. |
| dyslexic patients (Helenius it al., 1999; Temple et | | | | Since there were no significant group difference |
| al., 2001) | | | | during picture naming, the researchers concluded |
| Developmental dyslexia can be caused by | | | | that there were two different neural pathways |
| impairments in the phonological input system as | | | | governing both neurological functions: a |
| well as the phonological output system. | | | | phonological/orthographic system for word |
| Phonological deficits may affect | | | | reading, which is evidently impaired in dyslexic |
| grapheme-phoneme processing, as well as other | | | | children and a visual system for picture naming, |
| language related issues, such as phonological | | | | which can be unaffected in dyslexics. |
| awareness, phonological short-term memory and | | | | Overall, support shows different pathways for |
| verbal repetition. Several reports reveal that | | | | processing letter-related and visual information. |
| dyslexics display a good performance in purely | | | | This understanding may be important for |
| visual discrimination tasks not involving object | | | | dyslexics in relation to coping with everyday life |
| naming and letter strings naming. On the other | | | | demands and relevant skills training. |
| hand, there has been contradictory evidence with | | | | |