Top Lang Disorders Vol. 33, No. 4, pp. 298–312 Copyright c 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Working Memory Functioning in Children With Learning Disorders and Specific Language Impairment Kirsten Schuchardt, Ann-Katrin Bockmann, Galina Bornemann, and Claudia Maehler Purpose: On the basis of Baddeley’s working memory model (1986), we examined working mem- ory functioning in children with learning disorders with and without specific language impairment (SLI). We pursued the question whether children with learning disorders exhibit similar working memory deficits as children with additional SLI. Method: In separate analyses, we compared the following groups of children: (1) 30 children with dyslexia (DYS) and 16 children with DYS re- ceiving special language education and (2) 19 children with combined disorder of scholastic skills (CDSS) and 18 children with CDSS receiving special language education. A control group of 30 typically developing children was included in each comparison. All of the children receiving spe- cial language education met criteria for SLI. To assess the 3 subcomponents of working memory (phonological loop, visual–spatial sketchpad, central executive), the children worked individually on an extensive test battery. Results: We found deficits in the phonological loop and central executive functioning for children with dyslexia (and CDSS) as well as for children with additional SLI. Deficits in phonological functioning were broader and more profound for children with SLI. Deficits in visual–spatial sketchpad could only be found for children with CDSS without SLI. Con- clusions: Children with isolated learning disorder and children with additional SLI demonstrate similarities and differences in working memory functioning. These findings support our hypoth- esis that underlying working memory deficits for the different disorders partly overlap but also are distinct and partly distinguish between certain disorders. Key words: combined disorder of scholastic skills, dyslexia, learning disorder, specific language impairment, working memory EARNING DISORDERS REPRESENT one impairments in acquiring the cultural tech- L of the most frequent causes for school fail- niques of reading, spelling, and calculating. ure. Children with specific learning disorders Dyslexia describes specific deficits in read- such as dyslexia and dyscalculia show general ing acquisition (often combined with spelling disorder), and dyscalculia is characterized by deficits in arithmetic skills. The exact definitions and diagnostic cri- teria of learning disorders differ widely, but Author Affiliations: Department of Diagnostic and some sources are used commonly across the Educational Psychology (Drs Schuchardt, Bockmann, and Maehler and Ms Bornemann), world. International Classification of Dis- University of Hildesheim, Hildesheim, Germany. eases, Tenth Revision (ICD-10, 2011) by the The authors have indicated that they have no financial World Health Organization defines interna- and no nonfinancial relationships to disclose. tionally accepted diagnostic criteria. Here, Corresponding Author: Kirsten Schuchardt, PhD, learning disorders are described as poor per- Department of Diagnostic and Educational Psychol- formance in reading, spelling, and calculat- ogy, University of Hildesheim, Marienburger Platz 22, 31141, Hildesheim, Germany (schuchar@uni- ing, respectively, that must be significantly hildesheim.de). lower than expected with regard to age, in- DOI: 10.1097/01.TLD.0000437943.41140.36 telligence, and schooling. 298 Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Working Memory Functioning in Children With Learning Disorders and SLI 299 It is not unusual that learning disor- WORKING MEMORY ders occur together with specific language impairment (SLI), which is characterized by As possible causal factors underlying SLI serious qualitative and quantitative deficits and learning disorders, researchers have iden- in productive and/or receptive language pro- tified deficits in working memory and diverse ficiency. The ICD-10 (Code F80) defines aspects of phonological information process- “specific developmental disorders of speech ing, such as phonological awareness (Catts and language” as “disorders in which nor- et al., 2005; Eisenmajer, et al., 2005; Nithart mal patterns of language acquisition are dis- et al., 2009). Although various models of turbed from the early stages of develop- working memory have been developed, the ment.” It specifies further that the conditions model by Baddeley (1986) has proved a par- are not directly attributable to neurological ticularly useful theoretical tool in numerous or speech mechanism abnormalities, sensory studies in this area. The model distinguishes impairments, mental retardation, or environ- between different components of working mental factors. Specific developmental dis- memory, with the modality-free central ex- orders of speech and language are often ecutive acting as a kind of supervisory system followed by associated problems, such as that serves to control and regulate the cog- difficulties in reading and spelling. nitive processes occurring in its two limited- Approximately 25%–75% of all children capacity slave systems, the phonological loop with language impairment develop read- and the visual–spatial sketchpad. Further ing difficulties (Catts, Adlof, Hogan, & Ellis functions of the central executive that have Weismer, 2005; McArthur, Hogben, Edwards, since been identified by Baddeley (1996) in- Heath & Mengler, 2000; Tomblin, Zhang, clude coordinating the slave systems, focusing Buckwalter, & Catts, 2000). On the contrary, and switching attention, and retrieving repre- according to Catts et al. (2005), every fifth sentations from long-term memory. child with dyslexia shows a history of dif- In contrast, Baddeley’s (1986, 1996) two ficulties in language acquisition. If language slave systems perform modality-specific op- disorders persist until school age, the rate of erations. Verbal and auditory information children demonstrating specific reading dis- is stored temporarily and processed in the ability climbs to 50% (McArthur et al., 2000). phonological loop. Whereas verbal or audi- Children with SLI also can experience diffi- tory information enters the phonological store culties. These difficulties can emerge prior directly, visual information has to be trans- to formal schooling and persist during the lated into phonological code before it can school-age years (Cowan, Donlan, Newton, do so. Two components of the phonologi- & Lloyd, 2005; Donlan, Cowan, Newton, & cal loop are distinguished: the phonological Lloyd, 2007; Eisenmajer, Ross, & Pratt, 2005; store and the subvocal rehearsal process. The Fazio, 1994, 1996, 1999). visual–spatial sketchpad is concerned with re- Given this high comorbidity rate, recent re- membering and processing visual and spatial search has started to investigate the common- information; it comprises a visual cache for alities and shared causal factors of learning static visual information and an inner scribe disorders and SLI. Within recent years, one for dynamic spatial information (Logie, 1995; question has been addressed in particular: Are Pickering, Gathercole, Hall, & Lloyd, 2001). SLI and learning disabilities distinct disorders Later, Baddeley (2000) added a fourth com- with different causal factors or are they var- ponent to the working memory model, the ious manifestations of the same underlying episodic buffer, for linking long-term mem- cognitive factors (Baird, Slonims, Simonoff, & ory and integrating information from all of the Dworzynski, 2011; Catts et al., 2005; de Bree, other systems into a unified experience. To Wijnen, & Gerrits, 2010)? date, however, research on working memory Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 300 TOPICS IN LANGUAGE DISORDERS/OCTOBER–DECEMBER 2013 has mostly focused on the three original sub- Deficits in working memory functioning components, probably because it turned out have been investigated extensively also for to be difficult to create valid tasks measuring children with SLI. Children with SLI display the functioning of the episodic buffer. severe deficits in phonological loop function- ing (Archibald & Gathercole, 2006b, 2007; WORKING MEMORY AND LEARNING Marton & Schwartz, 2003). Results concern- DISORDERS ing visual working memory are inconsistent. Although some studies did not find any impair- There is considerable evidence that chil- ment of visual spatial sketchpad in children dren with dyslexia have deficits in phono- with SLI (e.g., Archibald & Gathercole, 2006a; logical processing and storage (Schuchardt, Riccio, Cash, & Cohen, 2007), others have re- Maehler, & Hasselhorn, 2008; Vellutino, ported significantly lower scores for children Fletcher, Snowling, & Scanlon, 2004). Chil- with SLI on tasks assessing the visual spatial dren have been found to exhibit a reduced sketchpad than those for typically develop- memory span for acoustically presented ing children (e.g., Hick, Botting, & Conti- words, numbers, and nonwords. Numerous Ramsden, 2005; Hoffman & Gillam, 2004). studies on dyslexia and accompanying deficits In addition to these phonological and visual– in complex abilities such as text comprehen- spatial difficulties exhibited by children with sion also detect deficits in central-executive SLI, deficits in central–executive processing working memory functioning (Landerl, Bevan are evident (Archibald