Sensory experience modulates the reorganization of auditory regions for executive processing.

Crossmodal plasticity refers to the reorganization of sensory cortices in the absence of their typical main sensory input. Understanding this phenomenon provides insights into brain function and its potential for change and enhancement. Using functional MRI, we investigated how early deafness influences crossmodal plasticity and the organization of executive functions in the adult human brain. Deaf (n = 25; age: mean = 41.68, range = 19-66, SD = 14.38; 16 female, 9 male) and hearing (n = 20; age: mean = 37.50, range = 18-66, SD = 16.85; 15 female, 5 male) participants performed four visual tasks tapping into different components of executive processing: task switching, working memory, planning and inhibition. Our results show that deaf individuals specifically recruit 'auditory' regions during task switching. Neural activity in superior temporal regions, most significantly in the right hemisphere, are good predictors of behavioural performance during task switching in the group of deaf individuals, highlighting the functional relevance of the observed cortical reorganization. Our results show executive processing in typically sensory regions, suggesting that the development and ultimate role of brain regions are influenced by perceptual environmental experience.

Executive Function in Deaf Native Signing Children.

The aim of this study is twofold: To examine if deafness is invariably associated with deficits in executive function (EF) and to investigate the relationship between sign language proficiency and EF in deaf children of deaf parents with early exposure to a sign language. It is also the first study of EF in children acquiring Polish Sign Language. Even though the mothers of the deaf children (N = 20) had lower levels of education compared with the mothers of a hearing control group, the children performed similarly to their hearing peers (N = 20) on a variety of EF task-based assessments. Only in the Go/No-go task were weaker inhibition skills observed in younger deaf children (6-9 years) compared with hearing peers, and this difference was not seen in older children (10-12 years). Hence, deafness does not necessarily impair EF; however, attentional and inhibition abilities may be acquired via a different route in deaf children. Sign language receptive skills predicted EF in deaf children. In conclusion, we highlight the importance of deaf parenting building the scaffolding for EF in deaf children.

Deaf Language Specialists: Delivering Language Therapy in Signed Languages.

Deaf professionals, whom we term Deaf Language Specialists (DLS), are frequently employed to work with children and young people who have difficulties learning sign language, but there are few accounts of this work in the literature. Through questionnaires and focus groups, 23 DLSs described their work in this area. Deductive thematic analysis was used to identify how this compared to the work of professionals (typically Speech and Language Therapists/Pathologists, SLPs) working with hearing children with difficulties learning spoken language. Inductive thematic analysis resulted in the identification of two additional themes: while many practices by DLSs are similar to those of SLPs working with hearing children, a lack of training, information, and resources hampers their work; additionally, the cultural context of language and deafness makes this a complex and demanding area of work. These findings add to the limited literature on providing language interventions in the signed modality with clinical implications for meeting the needs of deaf and hard-of-hearing children who do not achieve expectations of learning a first language in their early years. The use of these initial results in two further study phases to co-deliver interventions and co-produce training for DLSs is briefly described.

Differential coding of perception in the world's languages.

Is there a universal hierarchy of the senses, such that some senses (e.g., vision) are more accessible to consciousness and linguistic description than others (e.g., smell)? The long-standing presumption in Western thought has been that vision and audition are more objective than the other senses, serving as the basis of knowledge and understanding, whereas touch, taste, and smell are crude and of little value. This predicts that humans ought to be better at communicating about sight and hearing than the other senses, and decades of work based on English and related languages certainly suggests this is true. However, how well does this reflect the diversity of languages and communities worldwide? To test whether there is a universal hierarchy of the senses, stimuli from the five basic senses were used to elicit descriptions in 20 diverse languages, including 3 unrelated sign languages. We found that languages differ fundamentally in which sensory domains they linguistically code systematically, and how they do so. The tendency for better coding in some domains can be explained in part by cultural preoccupations. Although languages seem free to elaborate specific sensory domains, some general tendencies emerge: for example, with some exceptions, smell is poorly coded. The surprise is that, despite the gradual phylogenetic accumulation of the senses, and the imbalances in the neural tissue dedicated to them, no single hierarchy of the senses imposes itself upon language.

The effect of dopamine on the comprehension of spectrally-shifted noise-vocoded speech: a pilot study.

Objectives: Cochlear implantation has proven beneficial in restoring hearing. However, success is variable, and there is a need for a simple post-implantation therapy that could significantly increase implantation success. Dopamine has a general role in learning and in assigning value to environmental stimuli. We tested the effect of dopamine in the comprehension of spectrally-shifted noise-vocoded (SSNV) speech, which simulates, in hearing individuals, the signal delivered by a cochlear implant (CI).Design and study sample: Thirty-five participants (age = 38.0 ± 10.1 SD) recruited from the general population were divided into three groups. We tested SSNV speech comprehension in two experimental sessions. In one session, a metabolic precursor of dopamine (L-DOPA) was administered to participants in two of the groups; a placebo was administered in the other session.Results: A single dose of L-DOPA interacted with training to improve perception of SSNV speech, but did not significantly accelerate learning.Conclusions: These findings are a first step in exploring the use of dopamine to enhance speech understanding in CI patients. Replications of these results using SSNV in individuals with normal hearing, and also in CI users, are needed to determine whether these effects can translate into benefits in everyday language comprehension.

The Organization of Working Memory Networks is Shaped by Early Sensory Experience.

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.

Atypical maternal cradling laterality in an impoverished South African population.

Human studies consistently report a 60%-80% maternal left cradling preference. The dominant explanation points to an engagement of the emotionally more-attuned right brain. In contrast, we found equal incidences of left (31.3%), right (34.3%) and no-preference (34.3%) cradling in an impoverished South African population living under adverse conditions characterized by extreme dangers. We found striking differences on the Parenting Stress Index (PSI) between mothers with no cradling laterality preference and mothers with either a left or right preference. In several mammals a homologous left preference becomes stronger when acute threats prevail, rendering the rightwards shift we observed under dangerous conditions seemingly paradoxical. We propose this paradox can be resolved in terms of life-history strategy theory which predicts reduced parental investment in chronically dangerous environments. We interpret our high PSI score findings in no-preference cradlers as indicative of poorer, or at least ambivalent, maternal coping which many studies show is typically associated with reduced emotional sensitivity and responsiveness. We suggest that the latter may be a psychological mechanism mediating a partial withdrawal of parental investment in response to an enduringly adverse environment. To the best of our knowledge, this is the first study investigating cradling laterality preferences in an adverse socioeconomic environment.

Sign, language, and gesture in the brain: Some comments.

In contrast with two widely held and contradictory views - that sign languages of deaf people are "just gestures," or that sign languages are "just like spoken languages" - the view from sign linguistics and developmental research in cognition presented by Goldin-Meadow & Brentari (G-M&B) indicates a more complex picture. We propose that neuroscience research suggests that a similar approach needs to be taken and offer some examples from research on the brain bases of sign language perception.

Monitoring Different Phonological Parameters of Sign Language Engages the Same Cortical Language Network but Distinctive Perceptual Ones.

The study of signed languages allows the dissociation of sensorimotor and cognitive neural components of the language signal. Here we investigated the neurocognitive processes underlying the monitoring of two phonological parameters of sign languages: handshape and location. Our goal was to determine if brain regions processing sensorimotor characteristics of different phonological parameters of sign languages were also involved in phonological processing, with their activity being modulated by the linguistic content of manual actions. We conducted an fMRI experiment using manual actions varying in phonological structure and semantics: (1) signs of a familiar sign language (British Sign Language), (2) signs of an unfamiliar sign language (Swedish Sign Language), and (3) invented nonsigns that violate the phonological rules of British Sign Language and Swedish Sign Language or consist of nonoccurring combinations of phonological parameters. Three groups of participants were tested: deaf native signers, deaf nonsigners, and hearing nonsigners. Results show that the linguistic processing of different phonological parameters of sign language is independent of the sensorimotor characteristics of the language signal. Handshape and location were processed by different perceptual and task-related brain networks but recruited the same language areas. The semantic content of the stimuli did not influence this process, but phonological structure did, with nonsigns being associated with longer RTs and stronger activations in an action observation network in all participants and in the supramarginal gyrus exclusively in deaf signers. These results suggest higher processing demands for stimuli that contravene the phonological rules of a signed language, independently of previous knowledge of signed languages. We suggest that the phonological characteristics of a language may arise as a consequence of more efficient neural processing for its perception and production.

Differential activity in Heschl's gyrus between deaf and hearing individuals is due to auditory deprivation rather than language modality.

Sensory cortices undergo crossmodal reorganisation as a consequence of sensory deprivation. Congenital deafness in humans represents a particular case with respect to other types of sensory deprivation, because cortical reorganisation is not only a consequence of auditory deprivation, but also of language-driven mechanisms. Visual crossmodal plasticity has been found in secondary auditory cortices of deaf individuals, but it is still unclear if reorganisation also takes place in primary auditory areas, and how this relates to language modality and auditory deprivation. Here, we dissociated the effects of language modality and auditory deprivation on crossmodal plasticity in Heschl's gyrus as a whole, and in cytoarchitectonic region Te1.0 (likely to contain the core auditory cortex). Using fMRI, we measured the BOLD response to viewing sign language in congenitally or early deaf individuals with and without sign language knowledge, and in hearing controls. Results show that differences between hearing and deaf individuals are due to a reduction in activation caused by visual stimulation in the hearing group, which is more significant in Te1.0 than in Heschl's gyrus as a whole. Furthermore, differences between deaf and hearing groups are due to auditory deprivation, and there is no evidence that the modality of language used by deaf individuals contributes to crossmodal plasticity in Heschl's gyrus.

Synesthesia for manual alphabet letters and numeral signs in second-language users of signed languages.

Many synesthetes experience colors when viewing letters or digits. We document, for the first time, an analogous phenomenon among users of signed languages who showed color synesthesia for fingerspelled letters and signed numerals. Four synesthetes experienced colors when they viewed manual letters and numerals (in two cases, colors were subjectively projected on to the hands). There was a correspondence between the colors experienced for written graphemes and their manual counterparts, suggesting that the development of these two types of synesthesia is interdependent despite the fact that these systems are superficially distinct and rely on different perceptual recognition mechanisms in the brain.

Preexisting semantic representation improves working memory performance in the visuospatial domain.

Working memory (WM) for spoken language improves when the to-be-remembered items correspond to preexisting representations in long-term memory. We investigated whether this effect generalizes to the visuospatial domain by administering a visual n-back WM task to deaf signers and hearing signers, as well as to hearing nonsigners. Four different kinds of stimuli were presented: British Sign Language (BSL; familiar to the signers), Swedish Sign Language (SSL; unfamiliar), nonsigns, and nonlinguistic manual actions. The hearing signers performed better with BSL than with SSL, demonstrating a facilitatory effect of preexisting semantic representation. The deaf signers also performed better with BSL than with SSL, but only when WM load was high. No effect of preexisting phonological representation was detected. The deaf signers performed better than the hearing nonsigners with all sign-based materials, but this effect did not generalize to nonlinguistic manual actions. We argue that deaf signers, who are highly reliant on visual information for communication, develop expertise in processing sign-based items, even when those items do not have preexisting semantic or phonological representations. Preexisting semantic representation, however, enhances the quality of the gesture-based representations temporarily maintained in WM by this group, thereby releasing WM resources to deal with increased load. Hearing signers, on the other hand, may make strategic use of their speech-based representations for mnemonic purposes. The overall pattern of results is in line with flexible-resource models of WM.

Resting-state functional connectivity in deaf and hearing individuals and its link to executive processing.

Sensory experience shapes brain structure and function, and it is likely to influence the organisation of functional networks of the brain, including those involved in cognitive processing. Here we investigated the influence of early deafness on the organisation of resting-state networks of the brain and its relation to executive processing. We compared resting-state connectivity between deaf and hearing individuals across 18 functional networks and 400 ROIs. Our results showed significant group differences in connectivity between seeds of the auditory network and most large-scale networks of the brain, in particular the somatomotor and salience/ventral attention networks. When we investigated group differences in resting-state fMRI and their link to behavioural performance in executive function tasks (working memory, inhibition and switching), differences between groups were found in the connectivity of association networks of the brain, such as the salience/ventral attention and default-mode networks. These findings indicate that sensory experience influences not only the organisation of sensory networks, but that it also has a measurable impact on the organisation of association networks supporting cognitive processing. Overall, our findings suggest that different developmental pathways and functional organisation can support executive processing in the adult brain.

The road to language learning is iconic: evidence from British Sign Language.

An arbitrary link between linguistic form and meaning is generally considered a universal feature of language. However, iconic (i.e., nonarbitrary) mappings between properties of meaning and features of linguistic form are also widely present across languages, especially signed languages. Although recent research has shown a role for sign iconicity in language processing, research on the role of iconicity in sign-language development has been mixed. In this article, we present clear evidence that iconicity plays a role in sign-language acquisition for both the comprehension and production of signs. Signed languages were taken as a starting point because they tend to encode a higher degree of iconic form-meaning mappings in their lexicons than spoken languages do, but our findings are more broadly applicable: Specifically, we hypothesize that iconicity is fundamental to all languages (signed and spoken) and that it serves to bridge the gap between linguistic form and human experience.

Early vocabulary development in deaf native signers: a British Sign Language adaptation of the communicative development inventories.

BACKGROUND: There is a dearth of assessments of sign language development in young deaf children. This study gathered age-related scores from a sample of deaf native signing children using an adapted version of the MacArthur-Bates CDI (Fenson et al., 1994). METHOD: Parental reports on children's receptive and expressive signing were collected longitudinally on 29 deaf native British Sign Language (BSL) users, aged 8-36 months, yielding 146 datasets. RESULTS: A smooth upward growth curve was obtained for early vocabulary development and percentile scores were derived. In the main, receptive scores were in advance of expressive scores. No gender bias was observed. Correlational analysis identified factors associated with vocabulary development, including parental education and mothers' training in BSL. Individual children's profiles showed a range of development and some evidence of a growth spurt. Clinical and research issues relating to the measure are discussed. CONCLUSIONS: The study has developed a valid, reliable measure of vocabulary development in BSL. Further research is needed to investigate the relationship between vocabulary acquisition in native and non-native signers.

Identifying specific language impairment in deaf children acquiring British Sign Language: implications for theory and practice.

This paper presents the first ever group study of specific language impairment (SLI) in users of sign language. A group of 50 children were referred to the study by teachers and speech and language therapists. Individuals who fitted pre-determined criteria for SLI were then systematically assessed. Here, we describe in detail the performance of 13 signing deaf children aged 5-14 years on normed tests of British Sign Language (BSL) sentence comprehension, repetition of nonsense signs, expressive grammar and narrative skills, alongside tests of non-verbal intelligence and fine motor control. Results show these children to have a significant language delay compared to their peers matched for age and language experience. This impaired development cannot be explained by poor exposure to BSL, or by lower general cognitive, social, or motor abilities. As is the case for SLI in spoken languages, we find heterogeneity within the group in terms of which aspects of language are affected and the severity of the impairment. We discuss the implications of the existence of language impairments in a sign language for theories of SLI and clinical practice.

The signing brain: the neurobiology of sign language.

Most of our knowledge about the neurobiological bases of language comes from studies of spoken languages. By studying signed languages, we can determine whether what we have learnt so far is characteristic of language per se or whether it is specific to languages that are spoken and heard. Overwhelmingly, lesion and neuroimaging studies indicate that the neural systems supporting signed and spoken language are very similar: both involve a predominantly left-lateralised perisylvian network. Recent studies have also highlighted processing differences between languages in these different modalities. These studies provide rich insights into language and communication processes in deaf and hearing people.

The effects of cerebellar ataxia on sign language production: a case study.

Speech and sign production both require precise coordination of multiple articulators. The characteristics of dysarthria following ataxia have been well-documented, but less is known about the consequences of ataxia for sign language, which uses the hands and arms as articulators. This is the first study to examine ataxic dysarthria in a sign language user. What is novel in this research is that the limbs are employed for both linguistic and non-linguistic movements. Notably, sign production deficits broadly resembled ataxic dysarthria, while non-linguistic movement deficits were similar to those previously reported for ataxic limb movement.

Cerebral lateralisation during signed and spoken language production in children born deaf.

The effect of sensory experience on hemispheric specialisation for language production is not well understood. Children born deaf, including those who have cochlear implants, have drastically different perceptual experiences of language than their hearing peers. Using functional transcranial Doppler sonography (fTCD), we measured lateralisation during language production in a heterogeneous group of 19 deaf children and in 19 hearing children, matched on language ability. In children born deaf, we observed significant left lateralisation during language production (British Sign Language, spoken English, or a combination of languages). There was no difference in the strength of lateralisation between deaf and hearing groups. Comparable proportions of children were categorised as left-, right-, or not significantly-lateralised in each group. Moreover, an exploratory subgroup analysis showed no significant difference in lateralisation between deaf children with cochlear implants and those without. These data suggest that the processes underpinning language production remain robustly left lateralised regardless of sensory language experience.

Real Time Hand Movement Trajectory Tracking for Enhancing Dementia Screening in Ageing Deaf Signers of British Sign Language.

Real time hand movement trajectory tracking based on machine learning approaches may assist the early identification of dementia in ageing Deaf individuals who are users of British Sign Language (BSL), since there are few clinicians with appropriate communication skills, and a shortage of sign language interpreters. Unlike other computer vision systems used in dementia stage assessment such as RGBD video with the aid of depth camera, activities of daily living (ADL) monitored by information and communication technologies (ICT) facilities, or X-Ray, computed tomography (CT), and magnetic resonance imaging (MRI) images fed to machine learning algorithms, the system developed here focuses on analysing the sign language space envelope (sign trajectories/depth/speed) and facial expression of deaf individuals, using normal 2D videos. In this work, we are interested in providing a more accurate segmentation of objects of interest in relation to the background, so that accurate real-time hand trajectories (path of the trajectory and speed) can be achieved. The paper presents and evaluates two types of hand movement trajectory models. In the first model, the hand sign trajectory is tracked by implementing skin colour segmentation. In the second model, the hand sign trajectory is tracked using Part Affinity Fields based on the OpenPose Skeleton Model [1, 2]. Comparisons of results between the two different models demonstrate that the second model provides enhanced improvements in terms of tracking accuracy and robustness of tracking. The pattern differences in facial and trajectory motion data achieved from the presented models will be beneficial not only for screening of deaf individuals for dementia, but also for assessment of other acquired neurological impairments associated with motor changes, for example, stroke and Parkinson's disease.