An Overlooked Cause of Writing Impairment in People with Aphasia

Abstract

People with aphasia often have difficulties with writing (spelling) as part of their language impairment. In this paper, we focus on a type of spelling difficulty that is caused by an impairment to a particular part of the spelling process: a component of orthographic working memory, the graphemic output buffer. We describe the function of the graphemic buffer within the process of spelling, and present the characteristics of impairment to this component. Furthermore, we provide guidelines for assessment of spelling performance to enable identification of the source of spelling difficulties in clinical practice, and give an overview of different approaches to treatment of spelling difficulties as a result of buffer impairment.

Keywords:

• Dysgraphia
• Graphemic Output Buffer
• Orthographic Working Memory
• Spelling
• Writing

Notes

1 Written word production can include a variety of input and output modalities, e.g., writing to dictation, written naming, copying, typing, or free writing. We use “spelling” as an overarching term throughout the paper and specify the particular input/output modality where required.

2 In this paper we mostly report studies with individuals with stroke-aphasia; however, see Graham (2014) for a review on dysgraphia in progressive aphasia. Furthermore, the same subtypes of dysgraphia, including graphemic buffer impairment, have been reported in the developmental dysgraphia literature (see McCloskey & Rapp (2017) for an overview).

3 Graphemes are the letters that correspond to an individual phoneme, e.g., the three phonemes in the word ROCK are represented by the graphemes R, O, and CK.

4 It should be noted that the label “regular” may not be straightforward as some of these words contain phonemes that can map onto multiple, common, graphemes. For example, the phoneme /ee/ could be spelled using EA, EE or E.E: meat, meet, Pete. This inconsistency of phoneme-grapheme correspondences can be complicated even further when certain spellings are more common depending on context (e.g., the phoneme /ai/ is most frequently spelled AY in the final position of a word [lay], but as A.E when followed by another phoneme [late]). Spelling performance has been shown to be influenced by these factors, and therefore it is possible that in surface dysgraphia not all “regular” words will be spelled accurately.

5 Impairments to auditory input processes (phonological input buffer, phonological input lexicon) will also impact spelling to dictation, but would not result in impairments to written naming. This reinforces the importance of converging evidence in assessment to ensure accurate diagnosis of the source of the spelling problem within the language system.

6 Note that while spelling is expected to be impaired for all tasks, modalities and word types, and similar error types should be apparent, there may nevertheless be differences in the level of accuracy – different tasks/ modalities/word types have different demands that influence performance. For example, words are often more accurate than nonwords because they receive “support” from the stored lexical entry. Similarly, writing to dictation may be more accurate than written naming as the word form is provided rather than needing to be retrieved from the lexicon.

7 As regular words are able to be spelled using both lexical and sub-lexical routes they provide less clear diagnostic information than irregular words.

Additional information

Notes on contributors

Trudy Krajenbrink

Dr Trudy Krajenbrink is a researcher in the area of acquired language impairment.

Saskia Kohnen

Dr Saskia Kohnen is a senior researcher at Macquarie University and clinical director of the Macquarie University Reading Clinic.

Lyndsey Nickels

Prof Lyndsey Nickels is a research speech pathologist and professor at Macquarie University.