Phonology and handedness in primary school: predictions of the right shift theory

Abnormal interactions of verbal- and spatial-memory networks in young people at familial high-risk for schizophrenia

BACKGROUND

Working memory impairment (especially in verbal and spatial domains) is the core neurocognitive impairment in schizophrenia and the familial high-risk (FHR) population. Inconsistent results have been reported in clinical and neuroimaging studies examining the verbal- and spatial-memory deficits in the FHR subjects, due to sample differences and lack of understanding on interactions of the brain regions for processing verbal- and spatial-working memory.

METHODS

Functional MRI data acquired during a verbal- vs. spatial-memory task were included from 51 young adults [26 FHR and 25 controls]. Group comparisons were conducted in brain activation patterns responding to 1) verbal-memory condition (A), 2) spatial-memory condition (B), 3) verbal higher than spatial (A-B), 4) spatial higher than verbal (B-A), 5) conjunction of brain regions that were activated during both A and B (A∧B). Group difference of the laterality index (LI) in inferior frontal lobe for condition A was also assessed.

RESULTS

Compared to controls, the FHR group exhibited significantly decreased brain activity in left inferior frontal during A, and significantly stronger involvement of ACC, PCC, paracentral gyrus for the contrast of A-B. The LI showed a trend of reduced left-higher-than-right pattern for verbal-memory processing in the HR group.

CONCLUSIONS

Our findings suggest that in the entire functional brain network for working-memory processing, verbal information processing associated brain pathways are significantly altered in people at familial high risk for developing schizophrenia. Future studies will need to examine whether these alterations may indicate vulnerability for predicting the onset of Schizophrenia.

Does degree of handedness in a group of right-handed individuals affect language comprehension?

The impact of handedness on language processing has been studied extensively and the results indicate that there is a relationship between the two variables; however, the nature of the relationship is not at all clear. In the current study we explored degree of handedness (DH) opposed to direction in a group of right-handed individuals. fMRI was used to explore the impact of DH on the sentence comprehension network. The results revealed that during sentence comprehension activation in regions linked to semantic memory (e.g., anterior temporal cortex) were modulated by DH. Also, unexpectedly the precuneus/posterior cingulate gyrus which has been linked to episodic memory was also affected by DH. These results extend those reported previously by showing that the neural architecture that supports sentence comprehension is modulated by DH. More specifically, together the results presented here support the hypothesis proposed by Townsend, Carrithers, and Bever (2001) that DH interacts with the language system and impacts the strategy used during sentence comprehension.

Does cerebral lateralization develop? A study using functional transcranial Doppler ultrasound assessing lateralization for language production and visuospatial memory

In the majority of people, language production is lateralized to the left cerebral hemisphere and visuospatial skills to the right. However, questions remain as to when, how, and why humans arrive at this division of labor. In this study, we assessed cerebral lateralization for language production and for visuospatial memory using functional transcranial Doppler ultrasound in a group of 60 typically developing children between the ages of six and 16 years. The typical pattern of left-lateralized activation for language production and right-lateralized activation for visuospatial memory was found in the majority of the children (58%). No age-related change in direction or strength of lateralization was found for language production. In contrast, the strength of lateralization (independent of direction) for visuospatial memory function continued to increase with age. In addition, boys showed a trend for stronger right-hemisphere lateralization for visuospatial memory than girls, but there was no gender effect on language laterality. We tested whether having language and visuospatial functions in the same hemisphere was associated with poor cognitive performance and found no evidence for this "functional crowding" hypothesis. We did, however, find that children with left-lateralized language production had higher vocabulary and nonword reading age-adjusted standard scores than other children, regardless of the laterality of visuospatial memory. Thus, a link between language function and left-hemisphere lateralization exists, and cannot be explained in terms of maturational change.

Dyslexia and Handedness: Developmental Phonological and Surface Dyslexias are Associated with Different Biases for Handedness

Developmental disorders of reading and spelling have long been associated with increased left- and mixed-handedness but the evidence has been controversial. The right shift (RS) theory of handedness and cerebral dominance, developed by Annett from 1972 onward, offers resolutions to several puzzles about laterality in the so-called dyslexias. This review of findings in the light of the theory shows that “phonological” dyslexies are less likely to be right-handed, while “surface” or “dyseidetic” dyslexies are more likely to be right-handed than the general population.

Lateralidade manual, ocular e dos membros inferiores e sua relação com déficit de organização espacial em escolares

Este estudo teve por objetivos: 1) verificar se existe associação entre lateralidade manual, ocular e dos membros inferiores e déficit de organização espacial em escolares; 2) categorizar as variações de lateralidade nesta população. A amostra foi constituída de 400 crianças na faixa etária de 6 a 10 anos de escolas públicas e privadas da cidade de João Pessoa (PB). A lateralidade e a organização espacial foram avaliadas, respectivamente, por meio do Harris Test of Lateral Dominance e da Bateria de Piaget-Head. Os resultados evidenciaram 23 tipos de lateralidade mão-olho-pé, observando-se maior percentual (48,75%) de destralidade completa (dominância manual, ocular e dos membros inferiores direita). Houve associação significativa (p<0,05) entre sinistralidade completa e déficit de organização espacial. Os resultados atentam para a importância de se inserirem no cotidiano escolar programas de estimulação motora voltados à lateralidade e à organização espacial das crianças, como forma de prevenir distorções no seu processo de aprendizagem.