Lecture Notes on Writing and Dysgraphia

Identify the major components in our cognitive model of writing, specifically the central and peripheral components.
Understand the evidence related to subsystems of the cognitive model from cases of acquired dysgraphia, illustrating evidence of dissociations.
Characterize the neural substrates associated with the major components of writing.

Writing: An expressive form of language similar to reading, which involves creating orthographic expressions.
Key forms:
- Handwriting
- Typing
Requires:
- Manual skills
- Knowledge of spelling conventions
Historical context: Up until the 20th century, a significant portion of the population did not need to write; however, it is now a fundamental requirement for many activities.
Writing has been underexplored in academic discourse compared to reading.

Speech Input Processing:
  1. Auditory feature analysis.
  2. Phoneme system recognition.
  3. Activation of the phonological lexicon for word sound structures.
Spelling patterns are accessed from the orthographic lexicon, which helps determine the appropriate sequences of graphemes.
Writing can be prompted directly by speech or the semantic system, allowing for flexible routes during composition.
  - Routes for Spelling Retrieval:
    - Direct addition from phonological lexicon to orthographic lexicon.
    - Engagement of the semantic system when writing from inner thoughts or feelings.
Graphemic Buffer: A limited-capacity working memory that temporarily holds grapheme identities and positions until the word is written, receiving input from both the orthographic lexicon and phoneme-grapheme conversion systems.
Phoneme-Grapheme Conversion:
- Mapping phonemes to appropriate graphemes, allowing novel expressions to be conveyed in writing.
- Important for regular (e.g., desk) vs. irregular mappings (requiring access to the orthographic lexicon when exceptions occur).
Allographic Conversion: Converts abstract letter identities into concrete forms before relaying instructions to the hand or computer.

Dysgraphia: A neurological disorder characterized by impaired writing abilities and fine motor skills, often likened to “the dyslexia of writing.”
  - Phonological Dysgraphia: Impairment in writing pseudowords but not real words (e.g., inability to write 'yawt').
  - Surface Dysgraphia: Impairment in writing irregular real words but not regular words or pseudowords (e.g., inability to write 'yacht').
  - Deep Dysgraphia: Impairment in both pseudowords and real words, with semantic errors more prevalent in abstract items.

Phonological Dysgraphia Evidence:
  - Involves reduced phonological processing capacity and affects reading and spelling.
  - Patient RG: Poor at reading pseudowords but could spell real words accurately.
  - Patient MH: Could read pseudowords but struggled to spell them despite high reading accuracy.
Surface Dysgraphia Evidence:
- Performs well with pseudowords; struggles with sight-written words.
- Examples include misspellings like 'YOT' for 'yacht' where phoneme-grapheme conversion is functional, but irregular spelling cannot be retrieved.