acquired central dysgraphia

Question 1

what is aquired central dysgraphia?

Answer 1

Acquired central dysgraphia is an acquired neurological disorder that causes difficulty with spelling or with spontaneous communication, and is often accompanied by other language disorders (Smet et al, 2011). Central dysgraphia (or central agraphia) occurs when there are impairments in both:
The linguistic stage of writing - involved in encoding auditory and visual information into symbols for letters of written words and mediated through the angular gyrus
and to the various motor and visualization skills involved in writing - where expression of written words and graphemes are articulated. This is mediated by Exner’s writing area of the frontal lobe (Lorch, 2013).

Question 2

plan

Answer 2

1. What is acquired central dysgraphia?
2. Writing single words ( stages and route)
3. problems with accessing routes
4. however

Question 3

writing single words- stages

Answer 3

According to Whitworth et al. (2014) who based their reasoning on the language processing model for single words from Patterson & Shewell, 1987 Logogen model, there are four necessary stages, or processes, involved in writing words. These include:
The semantic system (i.e. the store of word meanings)
The orthographic output lexicon (the store of the spelling of familiar words)
The graphemic output buffer ( the store of graphemic representation, with information of the case not specified)
Allographic realisation (spatial representations of letters in their different allographic forms, e.g. upper and lower case).
Then, once the words have been successfully realised through allographic realisation, there is a translations of allographs to motor patterns to create them (graphic motor planning) (Whitworth, 2014).

Question 4

routes intro and semantic lexical route

Answer 4

Routes
In order to reach this latter stage (i.e graphic motor planning stage), Whitworth (2014) describes, that it can be achieved by one of three routes. These includes the semantic lexical route, the sub-lexical route and the direct lexical route.
The semantic lexical route, involves activation from the semantic system and access to the word within the orthographic output lexicon and is necessary to correctly spell homophones (e.g pair and pear);

Question 5

sub-lexical route

Answer 5

The sub-lexical route (writing via phonological to graphemic conversion) involves the segmentation of a word into phonemes and then the translation of phonemes into graphemes. It is used for the writing to dictation of unfamiliar words and nonwords

Question 6

direct lexical route

Answer 6

finally, the direct lexical route, involves writing to dictation via a lexical but not semantic route. It does this by retrieving the word’s phonology from the phonological output lexicon and then activating the word within the orthographic output lexicon. As only real, known words are represented in this lexicon, this route can only process real words, irrespective of their sound to spelling regularity . This results in being able to write irregular words without semantic knowledge.

Question 7

problems with routes intro

Answer 7

However, for those those with acquired central dysgraphia, deficits affect one of the routes involved, through impairments to one of the linguistic systems or access to one of the systems that are involved in writing.
The specific type of central acquired dysgraphia depends on the location of the impairment and whether alternative routes, of this model, can be utilised. The main writing impairments have been traditionally characterised in terms of: deep dysgraphia, phonological dysgraphia and surface dysgraphia.

Question 8

deep dysgraphia

Answer 8

For example, deep dysgraphia, as was described by Bub & Kertesz, 1982, results from writing via an impaired semantic route. Here, access to the orthographic output lexicon is impaired with an additional deficit to the phonological-to-graphemic conversion. This means that people with deep central dysgraphia are forced to write by the direct lexical route. Because of this the defining feature of deep dysgraphia is the presence of semantic errors in writing e.g. time may be might go to ‘clock’ in writing from dictation. In addition, nonword spelling is impaired (because they have impaired access to the phonological-to-graphemic conversion used to write nonwords), high-imageability words are written more accurately than low imageability words and content words are written more fluently than function words. This is because high-imageability words and content words have broader contextual verbal support and greater contextual associations in semantic memory (Schwanenflugel & Shoben,1983).

Question 9

surface dysgraphia

Answer 9

In contrast to this, another type of dysgraphia - surface dysgraphia - as described by Beauvouis & Derouesne (1981) results from impairment to lexically mediated writing and impaired Semantic to Orthographic Output Lexicon mapping. However, unlike deep dysgraphia phonological-to-graphemic conversion is well preserved. This means that unlike, deep dysgraphia, in surface dysgraphia writing takes place primarily via the sublexical route. As a result there are a number of differences in the characteristic features of this impairment. For example regular words and nonwords are written more accurately than irregular words (they can correctly produce some high frequency and irregular words) and there is confusion between spelling of homophones e.g sail - sale (whitworth et al 2014).

Question 10

However

Answer 10

It is important to note that more often than not, individuals will show mixed pattern of impairment and pure subtypes, such as deep and surface dysgraphia, are rare (whitworth et al, 2014).