Lightening the Load: Perceptual Load Impairs Visual Detection in Typical Adults but Not in Autism

Autism spectrum disorder (ASD) research portrays a mixed picture of attentional abilities with demonstrations of enhancements (e.g., superior visual search) and deficits (e.g., higher distractibility). Here we test a potential resolution derived from the Load Theory of Attention (e.g., Lavie, 2005). In Load Theory, distractor processing depends on the perceptual load of the task and as such can only be eliminated under high load that engages full capacity. We hypothesize that ASD involves enhanced perceptual capacity, leading to the superior performance and increased distractor processing previously reported. Using a signal-detection paradigm, we test this directly and demonstrate that, under higher levels of load, perceptual sensitivity was reduced in typical adults but not in adults with ASD. These findings confirm our hypothesis and offer a promising solution to the previous discrepancies by suggesting that increased distractor processing in ASD results not from a filtering deficit but from enhanced perceptual capacity

Field Independence Associates with Mathematics and Science Performance in 5-to 10-Year-Olds after Accounting for Domain-General Factors

Field independence describes the extent to which individuals are influenced by context when trying to identify embedded targets. It associates with cognitive functioning and is a predictor of academic achievement. However, little is known about the neural and cognitive underpinnings of field independence that lead to these associations. Here, we investigated behavioral associations between two measures of field independence (Children's Embedded Figures Test [CEFT] and Design Organization Test [DOT]) and performance on tests of mathematics (reasoning and written arithmetic) and science (reasoning and scientific inquiry) in 135 children aged 5–10 years. There were strong associations between field independence and mathematics and science, which were largely explained by individual differences in age, intelligence, and verbal working memory. However, regression analyses indicated that after controlling for these variables, the CEFT explained additional variance on the mathematical reasoning and science tests, whereas the DOT predicted unique variance on the written arithmetic test

Activation in a Frontoparietal Cortical Network Underlies Individual Differences in the Performance of an Embedded Figures Task

The Embedded Figures Test (EFT) requires observers to search for a simple geometric shape hidden inside a more complex figure. Surprisingly, performance in the EFT is negatively correlated with susceptibility to illusions of spatial orientation, such as the Roelofs effect. Using fMRI, we previously demonstrated that regions in parietal cortex are involved in the contextual processing associated with the Roelofs task. In the present study, we found that similar parietal regions (superior parietal cortex and precuneus) were more active during the EFT than during a simple matching task. Importantly, these parietal activations overlapped with regions found to be involved during contextual processing in the Roelofs illusion. Additional parietal and frontal areas, in the right hemisphere, showed strong correlations between brain activity and behavioral performance during the search task. We propose that the posterior parietal regions are necessary for processing contextual information across many different, but related visuospatial tasks, with additional parietal and frontal regions serving to coordinate this processing in participants proficient in the task

Sex Differences and Autism: Brain Function during Verbal Fluency and Mental Rotation

Autism spectrum conditions (ASC) affect more males than females. This suggests that the neurobiology of autism: 1) may overlap with mechanisms underlying typical sex-differentiation or 2) alternately reflect sex-specificity in how autism is expressed in males and females. Here we used functional magnetic resonance imaging (fMRI) to test these alternate hypotheses. Fifteen men and fourteen women with Asperger syndrome (AS), and sixteen typically developing men and sixteen typically developing women underwent fMRI during performance of mental rotation and verbal fluency tasks. All groups performed the tasks equally well. On the verbal fluency task, despite equivalent task-performance, both males and females with AS showed enhanced activation of left occipitoparietal and inferior prefrontal activity compared to controls. During mental rotation, there was a significant diagnosis-by-sex interaction across occipital, temporal, parietal, middle frontal regions, with greater activation in AS males and typical females compared to AS females and typical males. These findings suggest a complex relationship between autism and sex that is differentially expressed in verbal and visuospatial domains

Visual illusions: An interesting tool to investigate developmental dyslexia and autism spectrum disorder

A visual illusion refers to a percept that is different in some aspect from the physical stimulus. Illusions are a powerful non-invasive tool for understanding the neurobiology of vision, telling us, indirectly, how the brain processes visual stimuli. There are some neurodevelopmental disorders characterized by visual deficits. Surprisingly, just a few studies investigated illusory perception in clinical populations. Our aim is to review the literature supporting a possible role for visual illusions in helping us understand the visual deficits in developmental dyslexia and autism spectrum disorder. Future studies could develop new tools – based on visual illusions – to identify an early risk for neurodevelopmental disorders

Doctor of Philosophy

dissertationIt is unknown if children with high-functioning autism (HFA) employ self-directed speech to guide motor sequencing and motor control, or if they can benefit from using self-directed speech when prompted to do so. Participants performed a three-movement sequence across three conditions: Natural Learning, Task-Congruent Verbalization (TCV), and Task-Incongruent Verbalization (TIV). TIV deleteriously impacted performance in the typically-developing group (TD; n= 22), and not the HFA group (n=21). TCV improved performance in both groups, but to a greater extent in the HFA group. These findings suggest that children with HFA do not initiate self-directed speech spontaneously, but can use language to guide behavior when prompted to do so

Through the Eyes of Children with Autism Spectrum Disorders

The latest findings in neuroscience show that the brain of the child with autism spectrum disorders (ASD) deviates from the typical development path since the prenatal period. We know that the mutation of certain genes alters the maturational trajectory of synaptic connections during early development, a period of maximum vulnerability in which the formation of neuronal circuits is highly plastic and depends on both genetic and environmental factors. A better understanding of the neurobiological bases of ASD will draw bridges, until recently insurmountable, between neuronal circuits and atypical behaviors in the classroom. In addition, it will allow us to better explore which are the critical periods of development where the intervention, both clinical and educational, in the child with ASD may be more effective.Los últimos hallazgos en neurociencia muestran que el cerebro del niño con trastorno del espectro autista (TEA) se desvía de la ruta típica del desarrollo ya desde el período prenatal. Sabemos que la mutación de ciertos genes altera la trayectoria madurativa de las conexiones sinápticas durante el desarrollo temprano, un periodo de máxima vulnerabilidad en el que la formación de circuitos neuronales es altamente plástica y dependiente tanto de factores genéticos como ambientales. Una mejor comprensión de las bases neurobiológicas del TEA trazará puentes, hasta hace poco insalvables, entre los circuitos neuronales y los comportamientos atípicos en el aula. Además, nos permitirá explorar mejor cuáles son los periodos críticos del desarrollo donde la intervención, tanto clínica como educativa, en el niño con TEA puede resultar más eficaz

A custom magnetoencephalography device reveals brain connectivity and high reading/decoding ability in children with autism

A subset of individuals with autism spectrum disorder (ASD) performs more proficiently on certain visual tasks than may be predicted by their general cognitive performances. However, in younger children with ASD (aged 5 to 7), preserved ability in these tasks and the neurophysiological correlates of their ability are not well documented. In the present study, we used a custom child-sized magnetoencephalography system and demonstrated that preserved ability in the visual reasoning task was associated with rightward lateralisation of the neurophysiological connectivity between the parietal and temporal regions in children with ASD. In addition, we demonstrated that higher reading/decoding ability was also associated with the same lateralisation in children with ASD. These neurophysiological correlates of visual tasks are considerably different from those that are observed in typically developing children. These findings indicate that children with ASD have inherently different neural pathways that contribute to their relatively preserved ability in visual tasks

Field independence associates with mathematics and science performance in 5- to 10-year-olds after accounting for domain-general factors

Field independence describes the extent to which individuals are influenced by context when trying to identify embedded targets. It associates with cognitive functioning and is a predictor of academic achievement. However, little is known about the neural and cognitive underpinnings of field independence which lead to these associations. Here we investigated behavioural associations between two measures of field independence (Children’s Embedded Figures Test (CEFT) and Design Organisation Test (DOT)) and performance on mathematics (reasoning and written arithmetic) and science tests (reasoning and scientific inquiry) in 135 children aged 5-10 years. There were strong associations between field independence and mathematics and science, which were largely explained by individual differences in age, IQ, and verbal working memory. However, regression analyses indicated that after controlling for these variables, the CEFT explained additional variance on the mathematical reasoning and science tests, whereas the DOT predicted unique variance on the written arithmetic test