JCPSLP Vol 22 No 1 2020

Expanding possibilities: Foci on reading and interdisciplinary practices

An overlooked cause of writing impairment in people with aphasia Characteristics, assessment and treatment of graphemic buffer impairment Trudy Krajenbrink, Saskia Kohnen, and Lyndsey Nickels

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. W riting is an invaluable means of communication in our society, especially considering the increase of digital communication via the internet and the use of smartphones. Many everyday tasks involve translating an idea or spoken message into written words (which we will call “spelling” 1 ), such as writing a birthday card, filling in a form, typing an e-mail or writing a dictated address. People with aphasia or primary progressive aphasia often have spelling problems as part of their impairment – this is known as acquired dysgraphia , and comes in many forms. In this paper, we give a brief overview of the cognitive processes involved in spelling, and the symptoms of impairments to these processes. We then focus on one component of spelling that is perhaps less well-known in clinical practice but that can also cause spelling impairment: the graphemic (or orthographic) output buffer , an orthographic working memory component, damage to which can cause profound spelling problems. We describe the graphemic buffer’s function, how buffer impairment can be identified, and possible approaches to treatment of buffer impairment. 2 Cognitive model of spelling The process of written word production consists of so-called “central” cognitive processes (e.g., the orthographic lexicon) as well as more “peripheral” processes that involve motor actions needed for the

chosen method of spelling (writing, typing, etc.; Purcell Turkeltraub, Eden, & Rapp, 2011). Most cognitive architectures of spelling (see Figure 1) assume that spelling to dictation can be achieved through different pathways (see e.g., Beeson and Rapcsak, 2002; Tainturier & Rapp, 2001). The lexical spelling route retrieves the spellings of familiar words from a long-term memory store (the orthographic lexicon). As nonwords and unfamiliar words do not have an entry in the lexicon, these have to be spelled using a process of converting the sounds within words (phonemes) into the corresponding letters (graphemes 3 ): the sub-lexical route. This route can also be used to spell familiar words that have spellings comprising “standard” phoneme-grapheme correspondences (e.g., / dog/ ➝ dog ). However, this process will result in errors for irregular words, because by definition, not all phonemes in irregular words are represented by their most common spelling. For example, the phoneme /e/ is most commonly spelled with the letter E; consequently, the irregular word said would be spelled incorrectly via the sub-lexical pathway because /e/ is spelled AI, not E. In addition, some authors suggest that the lexical spelling route can be split into two (e.g., Whitworth, Webster, & Howard, 2014), one going via the semantic system and the other linking the phonological input lexicon directly to the orthographic output lexicon, which enables the spelling of (irregular) words without accessing semantic knowledge. Importantly, only the lexical (semantic) route can be used for spontaneous writing – an idea is generated and mapped onto a word meaning in the semantic system before the word form is retrieved from the orthographic output lexicon. Each of these spelling routes, and spelling components, can be separately impaired (although many individuals have problems in both routes/multiple components; see Beeson [2004] for an overview of patterns of spelling impairments). Breakdown can occur at various points within the pathways, leading to distinct patterns of impairment and error types. Functioning of the routes can be assessed using spelling to dictation of irregular words and nonwords (see below for further discussion of spelling assessment). Lexical spelling problems Individuals with problems in the lexical spelling route have disproportionate difficulties with the spelling of irregular words (e.g., said, yacht, enough), compared to regular words 4 and nonwords. If these individuals have an intact sub-lexical spelling route they can use this route to spell, but this results in characteristic “regularisation”errors, also

KEYWORDS DYSGRAPHIA GRAPHEMIC

OUTPUT BUFFER ORTHOGRAPHIC

WORKING MEMORY SPELLING WRITING

THIS ARTICLE HAS BEEN PEER- REVIEWED

Trudy Krajenbrink (top), Saskia Kohnen (centre) and Lyndsey Nickels

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JCPSLP Volume 22, Number 1 2020

www.speechpathologyaustralia.org.au