VL14 VIsual Word Recognition

1. Primary visual cortex -> analysis of visual input

2. gyrus angularis -> graphem > phonem

   —> seems not to be involved in processes of normal visual word recognition

1. primary acoustic area -> analysis of spoken words

2. wernicke area -> semantic analysis of phonological code

3. fasciculus arcuatus -> repetition

4. Broca area -> speech production

5. motor cortex -> control of vocal tract muscles

1. visual feature units

2. ->letter units

then two paths

fast route: triade aus

• orthographic lexicon

• phonological lexicon

• semantic system

slow route: grapheme-phoneme rule system

both paths unite at phoneme system

• slow route usually for new words, low frequency and pseudowords

• direct route for high frequency

1. visual input excites….

   • feature detectors

   • letter detectors

   • word detectors

     —> mutual inhibition and top down feedback to letter level

proposal:

• processing of the visual form of the word in visual cortex

  • in pronounceable non words & real ones

  • not activated in false font & letter strings

• semantics in left inferior frontal gyrus

  • in real words

  • not in pseudowords

• visual word form area in left ventral visual path !

  
  

• ventral occipital temporal cortex

  —> vwfa is in ventral occipital temporal cortex

• man with stroke in area: could see text but letter by letter strategy to read

but:

• reading without the anterior vOT possible in patient born without left superiror temporal

—> but this is congenital lesion!! not eacquired, brain might be organised differently

• reduced gray matter in vwfa (fusiform gyrus)

• reduced BOLD activation in supramarginal gyrus and inferior temporal gyrus

• fast/direct route -> ventral occipito-temporal —> vwfa seems to be involved in direct route

• slow/indirect route -> low frequency & pseudowords -> grapheme-phoneme conversion -> left inferior frontal gyrus

• both structure and function compromised

• understanding the functional organization of visual-perceptual processing pathways

• recognizing words regardless of font and case and handwriting

• repetition priming effect

  • repeated word will elicit less activity the second time shown

  • repetition suppression!

  • s ame effect when word is written differently and when written the same —> shared representation

• VWFA has an abstract representation of the word

left ventral occipito temporal cortex

—> neural processing of written words is independent of

———> font, case and semantics

—> pre-lexical code used to access the mental lexicon?

• left ventral occipitotemporal cortex

• hierarchical organization of word sensitive regions in vwfa

• the more word-like the more anterior activation in the ventral stream! —> speaks for hierarchy

• phonological sensitivity emerges in more anterior regions of ventral occipitotemporal cortex

functional organization is not yet understood —> visual word FORM area may be too strong

• vwfa is hierarchical neuronal processing

1. local contrasts

2. oriented bars

3. local contours /letter fragments

4. letter shapes

5. bank of abstract letter detectors

6. local bigrams

7. small words & recurring substrings

• also sensitivity to spoken words in vOT

• phonological sensitivity in more anterior regions

• suggestion that people recode heard speech into orthographic code

  • pattamadilok et al. —> tms adaptation paradigm —> facilitating a lexical decision is within-modal and not cross modal

    —> vOT represents both orthographic and phonologcial but in different neuronal populations!