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Deaf signers use magnitude manipulatioin strategies for mulitplication: fMRI evidence
Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences.
Department of Clinical Neuroscience, Karolinska institute, Stockholm, Sweden.
Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences. Linköping University, The Swedish Institute for Disability Research.
Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences. Linköping University, The Swedish Institute for Disability Research.
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2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Evidence suggests that the lag reported in mathematics for deaf signers derives from difficulties related to the verbal system of number processing as described in the triple code model. For hearing individuals the verbal system has been shown to be recruited for both arithmetic and language tasks. In the present study we investigate for the first time neuronal representations of arithmetic in deaf signers. We examine if the neural network supporting arithmetic and language, including the horizontal portion of the intraparietal sulcus (HIPS), the superior parietal lobule (SPL) bilaterally, the left angular gyrus (AG), pars opercularis (POPE) and pars triangularis (PTRI) of the left inferior frontal gyrus (IFG), is differently recruited for deaf and hearing individuals. Imaging data were collected from 16 deaf signers and 16 well-matched hearing nonsigners, using the same stimulus material for all tasks, but with different cues. During multiplication, deaf signers recruited rHIPS more than hearing non-signers, suggesting greater involvement of magnitude manipulation processes related to the quantity system, whereas there was no evidence that the verbal system was recruited. Further, there was no support for the notion of a common representation of phonology for sign and speech as previously suggested.

Place, publisher, year, edition, pages
Keyword [en]
Arithmetic; phonology; fMRI; deaf; sign language; magnitude manipulation
National Category
Health Sciences
URN: urn:nbn:se:liu:diva-111560OAI: diva2:758038
Available from: 2014-10-24 Created: 2014-10-24 Last updated: 2014-10-24Bibliographically approved
In thesis
1. Dealing with Digits: Arithmetic, Memory and Phonology in Deaf Signers
Open this publication in new window or tab >>Dealing with Digits: Arithmetic, Memory and Phonology in Deaf Signers
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Deafness has been associated with poor abilities to deal with digits in the context of arithmetic and memory, and language modality-specific differences in the phonological similarity of digits have been shown to influence short-term memory (STM). Therefore, the overall aim of the present thesis was to find out whether language modality-specific differences in phonological processing between sign and speech can explain why deaf signers perform at lower levels than hearing peers when dealing with digits. To explore this aim, the role of phonological processing in digit-based arithmetic and memory tasks was investigated, using both behavioural and neuroimaging methods, in adult deaf signers and hearing non-signers, carefully matched on age, sex, education and non-verbal intelligence. To make task demands as equal as possible for both groups, and to control for material effects, arithmetic, phonological processing, STM and working memory (WM) were all assessed using the same presentation and response mode for both groups. The results suggested that in digit-based STM, phonological similarity of manual numerals causes deaf signers to perform more poorly than hearing non-signers. However, for  digit-based WM there was no difference between the groups, possibly due to differences in allocation of resources during WM. This indicates that similar WM for the two groups can be generalized from lexical items to digits. Further, we found that in the present work deaf signers performed better than expected and on a par with hearing peers on all arithmetic tasks, except for multiplication, possibly because the groups studied here were very carefully matched. However, the neural networks recruited for arithmetic and phonology differed between groups. During multiplication tasks, deaf signers showed an increased  reliance on cortex of the right parietal lobe complemented by the left inferior frontal gyrus. In contrast, hearing non-signers relied on cortex of the left frontal and parietal lobes during multiplication. This suggests that while hearing non-signers recruit phonology-dependent arithmetic fact retrieval processes for multiplication, deaf signers recruit non-verbal magnitude manipulation processes. For phonology, the hearing non-signers engaged left lateralized frontal and parietal areas within the classical perisylvian language network. In deaf signers, however, phonological processing was limited to cortex of the left occipital lobe, suggesting that sign-based phonological processing does not necessarily activate the classical language network. In conclusion, the findings of the present thesis suggest that language modality-specific differences between sign and speech in different ways can explain why deaf signers perform at lower levels than hearing non-signers on tasks that include dealing with digits.

Abstract [sv]

Dövhet har kopplats till bristande förmåga att hantera siffror inom områdena aritmetik och minne. Särskilt har språkmodalitetsspecifika skillnader i fonologisk likhet för siffror visat sig påverka korttidsminnet. Det övergripande syftet med den här avhandlingen var därför att undersöka om språkmodalitetsspecifika skillnader i fonologisk bearbetning mellan teckenoch talspråk kan förklara varför döva presterar sämre än hörande på sifferuppgifter. För att utforska det området undersöktes fonologisk bearbetning i sifferbaserade minnesuppgifter och aritmetik med hjälp av både beteendevetenskapliga metoder och hjärnavbildning hos grupper av teckenspråkiga döva och talspråkiga hörande som matchats noggrant på ålder, kön, utbildning och icke-verbal intelligens. För att testförhållandena skulle bli så likartade som möjligt för de båda grupperna, och för att förebygga materialeffekter, användes samma presentations- och svarssätt för båda grupperna. Resultaten visade att vid sifferbaserat korttidsminne påverkas de dövas prestation av de tecknade siffrornas fonologiska likhet. Däremot fanns det ingen skillnad mellan grupperna gällande sifferbaserat arbetsminne, vilket kan bero på att de båda grupperna fördelar sina kognitiva resurser på olika sätt. Dessutom fann vi att den grupp teckenspråkiga döva som deltog i studien presterade bättre på aritmetik än vad tidigare forskning visat och de skiljde sig bara från hörande på multiplikationsuppgifter, vilket kan bero på att grupperna var så noggrant matchade. Däremot fanns det skillnader mellan grupperna i vilka neurobiologiska nätverk som aktiverades vid aritmetik och fonologi. Vid multiplikationsuppgifter aktiverades cortex i höger parietallob och vänster frontallob för de teckenspråkiga döva, medan cortex i vänster frontal- och parietallob aktiverades för de talspråkiga hörande. Detta indikerar att de talspråkiga hörande förlitar sig på fonologiberoende minnesstrategier medan de teckenspråkiga döva förlitar sig på ickeverbal magnitudmanipulering och artikulatoriska processer. Under den fonologiska uppgiften aktiverade de talspråkiga hörande vänsterlateraliserade frontala och parietala områden inom det klassiska språknätverket. För de teckenspråkiga döva var fonologibearbetningen begränsad till cortex i vänster occipitallob, vilket tyder på att teckenspråksbaserad fonologi inte behöver aktivera det klassiska språknätverket. Sammanfattningsvis visar fynden i den här avhandlingen att språkmodalitetsspecifika skillnader mellan tecken- och talspråk på olika sätt kan förklara varför döva presterar sämre än hörande på vissa sifferbaserade uppgifter.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 70 p.
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 632Studies from the Swedish Institute for Disability Research, ISSN 1650-1128 ; 67
Adult deaf signers, phonology, arithmetic, short-term memory, working memory, neuro imaging, Vuxna teckenspråkiga döva, fonologi, aritmetik, korttidsminne, arbetsminne, hjärnavbildning
National Category
Other Medical Sciences Health Sciences
urn:nbn:se:liu:diva-111561 (URN)10.3384/diss.diva-111561 (DOI)978-91-7519-235-2 (print) (ISBN)
Public defence
2014-11-14, Key 1, Hus Key, Campus Valla, Linköpings universitet, Linköping, 13:00 (English)
Available from: 2014-10-24 Created: 2014-10-24 Last updated: 2014-11-04Bibliographically approved

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Andin, JosefineDahlström, ÖrjanRönnberg, JerkerRudner, Mary
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