Tessa Dekker

Genetic and environmental vulnerabilities in children with neurodevelopmental disorders

One might expect that children with varying genetic mutations or children raised in low socioeconomic status environments would display different deficits. Although this expectation may hold for phenotypic outcomes in older children and adults, cross-syndrome comparisons in infancy reveal many common neural and sociocognitive deficits. The challenge is to track dynamic trajectories over developmental time rather than focus on end states like in adult neuropsychological studies. We contrast the developmental and adult approaches with examples from the cognitive and social domains, and we conclude that static models of adult brain lesions cannot be used to account for the dynamics of change in genetic and environmentally induced disorders in children.

Dorsal and ventral stream activation and object recognition performance in school-age children

We explored how developing neural artifact and animal representations in the dorsal and ventral stream play a role in childrens increasingly more proficient interactions with objects. In thirty-three 6- to 10-year-old children and 11 adults, we used fMRI to track the development of (1) the cortical category preference for tools compared to animals and (2) the response to complex objects (as compared to scrambled objects) during a passive viewing task. In addition, we related a cognitive skill that improved substantially from age 6 to 10, namely the ability to recognize tools from unusual viewpoints, to the development of cortical object processing. In multiple complementary analyses we showed that those children who were better at recognizing tools from unusual viewpoints outside the scanner showed a reduced cortical response to tools and animals when viewed inside the scanner, bilaterally in intraparietal and inferotemporal cortex. In contrast, the cortical preference for tools in the dorsal and ventral visual stream did not predict object recognition performance, and was organized in an adult-like manner at six. While cortical tool preference did not change with age, the findings suggest that animal-preferring regions in the ventral visual stream may develop later, concordant with previous reports of a protracted development in similar regions for faces. We thus conclude that intraparietal and inferotemporal cortical networks that support aspects of object processing irrespective of tool or animal category, continue to develop during the school-age years and contribute to the development of object recognition skills during this period.

Late development of cue integration is linked to sensory fusion in cortex.

Summary Adults optimize perceptual judgements by integrating different types of sensory information [1, 2]. This engages specialized neural circuits that fuse signals from the same [3, 4, 5] or different [6] modalities. Whereas young children can use sensory cues independently, adult-like precision gains from cue combination only emerge around ages 10 to 11 years [7, 8, 9]. Why does it take so long to make best use of sensory information? Existing data cannot distinguish whether this (1) reflects surprisingly late changes in sensory processing (sensory integration mechanisms in the brain are still developing) or (2) depends on post-perceptual changes (integration in sensory cortex is adult-like, but higher-level decision processes do not access the information) [10]. We tested visual depth cue integration in the developing brain to distinguish these possibilities. We presented children aged 6–12 years with displays depicting depth from binocular disparity and relative motion and made measurements using psychophysics, retinotopic mapping, and pattern classification fMRI. Older children (>10.5 years) showed clear evidence for sensory fusion in V3B, a visual area thought to integrate depth cues in the adult brain [3, 4, 5]. By contrast, in younger children (<10.5 years), there was no evidence for sensory fusion in any visual area. This significant age difference was paired with a shift in perceptual performance around ages 10 to 11 years and could not be explained by motion artifacts, visual attention, or signal quality differences. Thus, whereas many basic visual processes mature early in childhood [11, 12], the brain circuits that fuse cues take a very long time to develop.

The dynamics of ontogeny: a neuroconstructivist perspective on genes, brains, cognition and behavior.

For years, the view that the human cognitive system is as a Swiss army knife with innately specified functional modules that come online one by one or can be impaired independently of other modules, has dominated cognitive science. In this chapter, we start out by questioning this view and argue it needs to be replaced by a dynamic neuroconstructivist approach in which genes, brain, behavior, and environment interact multidirectionally throughout development. Using examples from the recent literature, we then highlight how a static modular view of the brain remains deeply ingrained in (1) behavioral, (2) neuroimaging, and (3) genetics research on typical and atypical cognitive development. Finally, we discuss future contributions of the neuroconstructivist approach to developmental research in particular, and cognitive neuroscience in general.

Picturing words? Sensorimotor cortex activation for printed words in child and adult readers

Highlights • We tested how picture-like responses to printed words develop in the child cortex.• Tool versus animal pictures and their names engaged similar brain areas in adults.• The 7–10 year-old sensorimotor cortex showed specialization for picture categories.• But names evoked no similar BOLD patterns despite good reading in older children.• So, automatic picturing of words’ sensorimotor meanings takes years to develop.

Face processing in Williams syndrome is already atypical in infancy

Face processing is a crucial socio-cognitive ability. Is it acquired progressively or does it constitute an innately-specified, face-processing module? The latter would be supported if some individuals with seriously impaired intelligence nonetheless showed intact face-processing abilities. Some theorists claim that Williams syndrome (WS) provides such evidence since, despite IQs in the 50s, adolescents/adults with WS score in the normal range on standardized face-processing tests. Others argue that atypical neural and cognitive processes underlie WS face-processing proficiencies. But what about infants with WS? Do they start with typical face-processing abilities, with atypicality developing later, or are atypicalities already evident in infancy? We used an infant familiarization/novelty design and compared infants with WS to typically developing controls as well as to a group of infants with Down syndrome matched on both mental and chronological age. Participants were familiarized with a schematic face, after which they saw a novel face in which either the features (eye shape) were changed or just the configuration of the original features. Configural changes were processed successfully by controls, but not by infants with WS who were only sensitive to featural changes and who showed syndrome-specific profiles different from infants with the other neurodevelopmental disorder. Our findings indicate that theorists can no longer use the case of WS to support claims that evolution has endowed the human brain with an independent face-processing module.

Population receptive field tuning properties of visual cortex during childhood

Improvements in visuospatial perception such as contrast sensitivity and Vernier acuity continue until late in childhood, but the neural mechanisms driving these age-related changes are currently unclear. One contributing factor could be the protracted development of spatial tuning of neuronal populations across the visual cortex. Here we tested this possibility using population receptive field (pRF) mapping (Dumoulin and Wandell, 2008) in 6-to 12-year-old children and adults. We fitted pRF models to BOLD signals measured in areas V1-V4 and V3a during fMRI whilst participants watched wedge and ring stimuli traversing the visual field. Cortical magnification and the width of pRF tuning functions changed with viewing eccentricity in all participants. However, there were no age-related changes in pRF size, shape, cortical magnification, or map consistency across any of the visual areas measured. These results suggest that visuospatial perception in late childhood beyond age 6 years is not substantially limited by low-level spatial tuning properties of neuronal populations in visual cortex. Instead, performance improvements in this period may reflect more efficient use of the spatial information available in the visual system when forming perceptual judgments. These findings are an important step towards disentangling which neural mechanisms contribute to the eventual emergence of mature spatial vision, and for understanding the processes that determine the scope for visual plasticity at different stages of life.

Crossmodal integration : a glimpse into the development of sensory remapping.

Correctly localising sensory stimuli in space is a formidable challenge for the newborn brain. A new study provides a first glimpse into how human brain mechanisms for sensory remapping develop in the first year of life.

Object processing for action across childhood

Human adults process and select the opportunities for action in their environment rapidly, efficiently, and effortlessly. While several studies have revealed substantial improvements in object recognition skills, motor abilities, and control over the motor system during late childhood, surprisingly little is known about how object processing for action develops during this period. This study addresses this issue by investigating how the ability to ignore actions potentiated by a familiar utensil develops between ages 6 and 10 years. It is the first study to demonstrate that (1) the mechanisms that transform a graspable visual stimulus into an object-appropriate motor response are in place by the sixth year of life and (2) graspable features of an object can facilitate and interfere with manual responses in an adult-like manner by this age. The results suggest that there may be distinct developmental trajectories for the ability to ignore motor responses triggered by visual affordances and the stimulus response compatibility effects typically assessed with Simon tasks.

The Contrast Sensitivity Function in children: Bayesian adaptive estimation using QUEST+

Background Compared to visual acuity alone, the full Contrast Sensitivity Function (CSF) provides important clinical information that can be used for diagnosis and monitoring [1]. However, in clinical vision-science, we currently lack a robust, childfriendly measure of the CSF: current measures of CSF are too slow. Bayesian adaptive estimation (e.g., the “qCSF[2]”) provides faster and more robust measures than traditional psychophysical techniques.