Early deafness results in crossmodal reorganization of the superior temporal cortex (STC). Here, we investigated the effect of deafness on cognitive processing. Specifically, we studied the reorganization, due to deafness and sign language (SL) knowledge, of linguistic and nonlinguistic visual working memory (WM). We conducted an fMRI experiment in groups that differed in their hearing status and SL knowledge: deaf native signers, and hearing native signers, hearing nonsigners. Participants performed a 2-back WM task and a control task. Stimuli were signs from British Sign Language (BSL) or moving nonsense objects in the form of point-light displays. We found characteristic WM activations in fronto-parietal regions in all groups. However, deaf participants also recruited bilateral posterior STC during the WM task, independently of the linguistic content of the stimuli, and showed less activation in fronto-parietal regions. Resting-state connectivity analysis showed increased connectivity between frontal regions and STC in deaf compared to hearing individuals. WM for signs did not elicit differential activations, suggesting that SL WM does not rely on modality-specific linguistic processing. These findings suggest that WM networks are reorganized due to early deafness, and that the organization of cognitive networks is shaped by the nature of the sensory inputs available during development.

Deafness is generally associated with poor mental arithmetic, possibly due to neuronal differences in arithmetic processing across language modalities. Here, we investigated for the first time the neuronal networks supporting arithmetic processing in adult deaf signers. Deaf signing adults and hearing non-signing peers performed arithmetic and phonological tasks during fMRI scanning. At whole brain level, activation patterns were similar across groups. Region of interest analyses showed that although both groups activated phonological processing regions in the left inferior frontal gyrus to a similar extent during both phonological and multiplication tasks, deaf signers showed significantly more activation in the right horizontal portion of the inferior parietal sulcus. This region is associated with magnitude manipulation along the mental number line. This pattern of results suggests that deaf signers rely more on magnitude manipulation than hearing non-signers during multiplication, but that phonological involvement does not differ significantly between groups.Abbreviations: AAL: Automated Anatomy Labelling; fMRI: functional magnetic resonance imaging; HIPS: horizontal portion of the intraparietal sulcus; lAG: left angular gyrus; lIFG: left inferior frontal gyrus; rHIPS: right horizontal portion of the intraparietal sulcus ARTICLE HISTORY

Working memory (WM) for sign language has an architecture similar to that for speech-based languages at both functional and neural levels. However, there are some processing differences between language modalities that are not yet fully explained, although a number of hypotheses have been mooted. This article reviews some of the literature on differences in sensory, perceptual and cognitive processing systems induced by auditory deprivation and sign language use and discusses how these differences may contribute to differences in WM architecture for signed and speechbased languages. In conclusion, it is suggested that left-hemisphere reorganization of the motion-processing system as a result of native signlanguage use may interfere with the development of the order processing system in WM.

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Deaf students generally lag several years behind hearing peers in arithmetic, but little is known about the mechanisms behind this. In the present study we investigated how phonological skills interact with arithmetic. Eighteen deaf signers and eighteen hearing non-signers took part in an experiment that manipulated arithmetic and phonological knowledge in the language modalities of sign and speech. Independent tests of alphabetical and native language phonological skills were also administered. There was no difference in performance between groups on subtraction, but hearing non-signers performed better than deaf signers on multiplication. For the deaf signers but not the hearing non-signers, multiplicative reasoning was associated with both alphabetical and phonological skills. This indicates that deaf signing adults rely on language processes to solve multiplication tasks, possibly because automatization of multiplication is less well established in deaf adults

Arithmetic and language processing involve similar neural networks, but the relative engagement remains unclear. In the present study we used fMRI to compare activation for phonological, multiplication and subtraction tasks, keeping the stimulus material constant, within a predefined language-calculation network including left inferior frontal gyrus and angular gyrus (AG) as well as superior parietal lobule and the intraparietal sulcus bilaterally. Results revealed a generally left lateralized activation pattern within the language-calculation network for phonology and a bilateral activation pattern for arithmetic, and suggested regional differences between tasks. In particular, we found a more prominent role for phonology than arithmetic in pars opercularis of the left inferior frontal gyrus but domain generality in pars triangularis. Parietal activation patterns demonstrated greater engagement of the visual and quantity systems for calculation than language. This set of findings supports the notion of a common, but regionally differentiated, language-calculation network.

Similar working memory (WM) for lexical items has been demonstrated for signers and non-signers while short-term memory (STM) is regularly poorer in deaf than hearing individuals. In the present study, we investigated digit-based WM and STM in Swedish and British deaf signers and hearing non-signers. To maintain good experimental control we used printed stimuli throughout and held response mode constant across groups. We showed that deaf signers have similar digit-based WM performance, despite shorter digit spans, compared to well-matched hearing non-signers. We found no difference between signers and non-signers on STM span for letters chosen to minimize phonological similarity or in the effects of recall direction. This set of findings indicates that similar WM for signers and non-signers can be generalized from lexical items to digits and suggests that poorer STM in deaf signers compared to hearing non-signers may be due to differences in phonological similarity across the language modalities of sign and speech.

The literacy skills of deaf children generally lag behind those of their hearing peers. The mechanisms of reading in deaf individuals are only just beginning to be unraveled but it seems that native language skills play an important role. In this study 12 deaf pupils (six in grades 1-2 and six in grades 4-6) at a Swedish state primary school for deaf and hard of hearing children were trained on the connection between Swedish Sign Language and written Swedish using a pilot sign language version of the literacy training software program Omega-is. Literacy skills improved substantially across the 20 days of the study. These literacy gains may have rested upon the specific softwarebased intervention, upon regular classroom activities, or upon a combination of these factors. Omega-is-d, and similar software utilizing sign language as a component, targets an important mechanism supporting reading development in deaf children and could play an important role in bilingual education refinements.