Space by the numbers

Numerical and spatial abilities have been correlated on many occasions. People who tend to be more proficient at spatial tasks also tend to be more proficient at mathematical operations and understanding of numbers. The current work takes several approaches to describe this relationship in further detail by investigating the role of attentional systems and executive control with regards to the processing of numbers and quantities. In a first attempt to do so we provide two studies whose goal it was to replicate the classical association between Arabic digits and response modality (SNARC-effect) and the association between Arabic digits and attentional shifts (Attentional SNARC-effect). In two further studies, we investigated the role of the Attentional SNARC-effect with regards to visual processing and consciousness. In the first of these studies, we made use of a backwards-mask to obscure a single Arabic digit from conscious processing, resulting in the loss of its spatial association in a line-bisection task. Secondly, we used a novel binocular rivalry paradigm to suppress two lateral stimuli from conscious perception and found that the duration of suppression was influenced by the numerical magnitude of a single presented Arabic digit. Specifically, we found that a stimulus on the left side of space would return faster when the Arabic digit was lower than five and that the right side of space would exhibit the same effect when the Arabic digit was higher than five. A crucial manipulation in these last two experiments was an adaptation to the original paradigm for measuring the attentional SNARC-effect. By adding a control-question on the magnitude or parity at the end of each trial, we ensured that the spatial effects would occur during these experiments. Furthermore, this effectively turned the experiments into working-memory tasks. Finally, we tested the influence of a visuo-spatial working-memory task and an addition-task on fronto-parietal network associated with mathematical operations in an event-related fMRI-experiment. This experiment included members of three populations with different levels of mathematical proficiency (Children with Developmental Dyscalculia, Typically developing children and Typical Adults). We found that brain-areas associated with executive control and basic visual processing were affected differently for children with developmental dyscalculia, hinting at a deficiency in visuo-spatial processing in this particular group

A developmental model of number representation

We delineate a developmental model of number representations. Notably, developmental dyscalculia (DD) is rarely associated with an all-or-none deficit in numerosity processing as would be expected if assuming abstract number representations. Finally, we suggest that the "generalist genes” view might be a plausible - though thus far speculative - explanatory framework for our model of how number representations develo

Temporal processing in autism spectrum disorder and developmental dyslexia : a systematic review and meta-analysis

Les individus ayant un trouble du spectre de l’autisme (TSA) ou une dyslexie développementale (DD) semblent avoir des difficultés de traitement temporel. Ces difficultés peuvent avoir un impact sur des processus de haut-niveau, comme la communication, les compétences sociales, la lecture et l’écriture. La présente méta-analyse a examiné deux tests de traitement temporel afin de remplir les objectifs suivants: 1) déterminer si les difficultés de traitement temporel sont un trait commun au TSA et à la DD, et ce pour le traitement multisensoriel et unisensoriel, pour différentes modalités et types de stimuli, 2) d’évaluer la relation entre la sévérité clinique et le traitement temporel, et 3) d’examiner l’effet de l’âge sur le traitement temporel. Les résultats ont montré un déficit de traitement temporel dans le TSA et la DD, caractérisé de déficits multisensoriels chez ces deux populations, et de déficits unisensoriels auditifs, tactiles et visuels pour la DD. De plus, notre analyse de la sévérité clinique indique qu’un meilleur traitement temporel en DD est associé à de meilleures compétences en lecture. Enfin, les déficits de traitement temporel ne varient pas avec l’âge des individus TSA et DD, ils sont donc présents tout au long du développement et de la vie adulte. En conclusion, les résultats de la méta-analyse montrent que les difficultés de traitement temporel font partie du cadre clinique du TSA et de la DD et permettent d’émettre des recommandations pour de futures recherches et interventions.Individuals with autism spectrum disorder (ASD) or developmental dyslexia (DD) are commonly reported to have deficits in temporal processing. These deficits can impact higher-order processes, such as social communication, reading and writing. In this thesis, quantitative meta-analyses are used to examine two temporal processing tasks, with the following objectives: 1) determine whether temporal processing deficits are a consistent feature of ASD and DD across specific task contexts such as multisensory and unisensory processing, modality and stimulus type, 2) investigate the relationship between symptom severity and temporal processing, and 3) examine the effect of age on temporal processing deficits. The results provide strong evidence for impaired temporal processing in both ASD and DD, as measured by judgments of temporal order and simultaneity. Multisensory temporal processing was impaired for both ASD and DD, and unisensory auditory, tactile and visual processing was impaired in DD. Greater reading and spelling skills in DD were associated with greater temporal precision. Temporal deficits did not show changes with age in either disorder. In addition to more clearly defining temporal impairments in ASD and DD, the results highlight common and distinct patterns of temporal processing between these disorders. Deficits are discussed in relation to existing theoretical models, and recommendations are made for future research and interventions

A comparison of working memory profiles in HIV-infected and HIV-exposed uninfected children

A thesis submitted to the Faculty of Humanities (University of the Witwatersrand, Johannesburg), in fulfillment of the requirements for the degree of Doctor of Philosophy by thesis in the field of Psychology. University of the Witwatersrand, Johannesburg, 2015Conventional psychometric measures, such as the IQ score, have significant limitations in addressing the assessment needs of linguistically and culturally diverse communities. In response, working memory assessment has been identified as a promising alternative to these constraints. It is a better predictor of scholastic success than IQ, and is essential in the acquisition of fundamental literacy and numeracy concepts in school beginners. While there is a lot of theoretical and empirical support for working memory performance in typically developing populations, less is known about its functioning in the context of atypical development; particularly in children who are infected with, or exposed to HIV in utero. This study compared the working memory (AWMA) and general neuropsychological functioning (NEPSY-II) of 273 South African school beginners (6-8 years). The sample consisted of both HIV-infected (n = 95), and HIV-exposed (n = 86) children, as well as an uninfected, unexposed typically developing control group (n = 92). Significant differences were found between the three groups on measures of working memory and general neurocognitive functioning, where the processing component of working memory appeared to be particularly impaired in the two HIV-affected atypical groups. A within-group analysis of the relative strengths and weaknesses of each of the three groups showed that both storage and processing skills in the verbal domain appeared to be general weaknesses, while visuospatial working memory was a relative strength. The former is believed to be influenced by issues of linguistic test bias in the multilingual sample, while the latter is posited to be a consequence of this very multilingualism, which affords these children an executive functioning advantage. The two HIV-affected samples also showed significant deviations in the structure of their working memory when compared to the typically developing control group. However, within-group structural comparisons of a number of working memory models showed that the four factor model comprising separate components of the verbal and visuospatial simple and processing components of working memory was still favoured, even in conditions of atypical development. The study contributes to the growing body of working memory research by presenting the working memory profiles of HIV-infected and HIV-exposed, uninfected children. It also assists in identifying HIV-exposed, uninfected children as a vulnerable and under-researched clinical group which could benefit from further intervention, as well as foregrounding working memory as a less biased alternative in the assessment of paediatric cognitive functioning.MT201

A comparison of working memory profiles in HIV-infected and HIV-exposed uninfected children

A thesis submitted to the Faculty of Humanities (University of the Witwatersrand, Johannesburg), in fulfillment of the requirements for the degree of Doctor of Philosophy by thesis in the field of Psychology. University of the Witwatersrand, Johannesburg, 2015Conventional psychometric measures, such as the IQ score, have significant limitations in addressing the assessment needs of linguistically and culturally diverse communities. In response, working memory assessment has been identified as a promising alternative to these constraints. It is a better predictor of scholastic success than IQ, and is essential in the acquisition of fundamental literacy and numeracy concepts in school beginners. While there is a lot of theoretical and empirical support for working memory performance in typically developing populations, less is known about its functioning in the context of atypical development; particularly in children who are infected with, or exposed to HIV in utero. This study compared the working memory (AWMA) and general neuropsychological functioning (NEPSY-II) of 273 South African school beginners (6-8 years). The sample consisted of both HIV-infected (n = 95), and HIV-exposed (n = 86) children, as well as an uninfected, unexposed typically developing control group (n = 92). Significant differences were found between the three groups on measures of working memory and general neurocognitive functioning, where the processing component of working memory appeared to be particularly impaired in the two HIV-affected atypical groups. A within-group analysis of the relative strengths and weaknesses of each of the three groups showed that both storage and processing skills in the verbal domain appeared to be general weaknesses, while visuospatial working memory was a relative strength. The former is believed to be influenced by issues of linguistic test bias in the multilingual sample, while the latter is posited to be a consequence of this very multilingualism, which affords these children an executive functioning advantage. The two HIV-affected samples also showed significant deviations in the structure of their working memory when compared to the typically developing control group. However, within-group structural comparisons of a number of working memory models showed that the four factor model comprising separate components of the verbal and visuospatial simple and processing components of working memory was still favoured, even in conditions of atypical development. The study contributes to the growing body of working memory research by presenting the working memory profiles of HIV-infected and HIV-exposed, uninfected children. It also assists in identifying HIV-exposed, uninfected children as a vulnerable and under-researched clinical group which could benefit from further intervention, as well as foregrounding working memory as a less biased alternative in the assessment of paediatric cognitive functioning.MT201