Vision first? The development of primary visual cortical networks is more rapid than the development of primary motor networks in humans

Ultrasonic bone age fractionates cognitive abilities in adolescence

Adolescent development is not only shaped by the mere passing of time and accumulating experience, but it also depends on pubertal timing and the cascade of maturational processes orchestrated by gonadal hormones. Although individual variability in puberty onset confounds adolescent studies, it has not been efficiently controlled for. Here we introduce ultrasonic bone age assessment to estimate biological maturity and disentangle the independent effects of chronological and biological age on adolescent cognitive abilities. Comparing cognitive performance of female participants with different skeletal maturity we uncover the impact of biological age on both IQ and specific abilities. We find that biological age has a selective effect on abilities: more mature individuals within the same age group have higher working memory capacity and processing speed, while those with higher chronological age have better verbal abilities, independently of their maturity. Based on our findings, bone age is a promising biomarker of adolescent maturity.

Development of global visual processing: From the retina to the perceptive field

Young children exhibit poorer visual performance than adults due to immaturity of the fovea and of the fundamental processing of visual functions such as masking and crowding. Recent studies suggest that masking and crowding are closely related to the size of the fundamental processing unit-the perceptive field (PF). However, while it is known that the retina and basic visual functions develop throughout childhood, it is not clear whether and how changes in the size of the PF affect masking and crowding. Furthermore, no retinal and perceptual development data have been collected from the same cohort and time. Here we explored the developmental process of the PF and the basic visual functions. Psychophysical and imaging methods were used to test visual functions and foveal changes in participants ranging from 3-17 years old. Lateral masking, crowding and contrast sensitivity were tested using computerized tasks. Foveal measurements were obtained from spectral-domain optical coherence tomography (OCT). The children patterns below 6 years exhibited high crowding, while the expected facilitation was found only at a larger target-flanker distance than required for children above 6 years, who exhibited the typical adult. Foveal thickness and macular volume for the children below 6 years were significantly lower than for the older group. Significant correlation was found for contrast sensitivity, foveal thickness and macular volume with age and between contrast sensitivity and foveal thickness. Our data suggest that the developmental processes at the retina and visual cortex occur in the same age range. Thus, in parallel to maturation of the PF, which enables reduction in crowding, foveal development contributes to increasing contrast sensitivity.

Lutein and zeaxanthin: The possible contribution, mechanisms of action and implications of modern dietary intake for cognitive development in children

Background:Studies suggest that lutein and zeaxanthin may be important for cognitive development in children, but a comprehensive evidence synthesis is lacking. The purpose of this evidence synthesis was to analyse the available data regarding the role of lutein and zeaxanthin for cognition in children and propose a theoretical basis for future studies.Methods:The PubMed, Scopus, the ISRCTN registry and Cochrane Library databases were searched for studies that evaluated the relationship between lutein and zeaxanthin and cognitive function in children. Reference list and ancestry searches were performed on relevant articles. A total of 543 articles were identified, of which six cross-sectional studies were included.Results:The literature search revealed that the evidence concerning the effect of lutein and zeaxanthin on cognition in children is sparse. However, there is some preliminary evidence indicating a positive association between lutein and zeaxanthin and cognition in childhood.Conclusions:The cross-sectional nature of the few studies available and the lack of RCT data indicates a need for further investigation before any firm conclusions can be drawn.

Perceptual completion of partly occluded contours during childhood

An early functional onset of perceptual completion has been extensively documented during the first several months after birth. However, there is no indication for the developmental time periods at which these skills become fully developed. We used a version of an object-based attention task in which children and adults performed a same-different size judgment of two features appearing at two of four possible ends of overlapping objects. Single-object over two-object superiority (i.e., faster judgments when the features appeared on the same object than when they appeared on different objects) was observed for a complete object as early as at 4 years of age. However, it is only at 5 years of age that such a single-object advantage was obtained also for an occluded object, and even then the advantage of the single-object and occluded-object conditions over the two-object condition was observed only when the two features in the two-object condition were spatially distant, demonstrating the critical role of spatial proximity in perceptual organization during childhood. The results suggest that perceptual completion during infancy and early childhood demonstrates some rudimentary perceptual skills that become more firmly established with age.

The Effect of Local Orientation Change on the Detection of Contours Defined by Constant Curvature: Psychophysics and Image Statistics

In the present study, we investigated the detection of contours defined by constant curvature and the statistics of curved contours in natural scenes. In Experiment 1, we examined the degree to which human sensitivity to contours is affected by changing the curvature angle and disrupting contour curvature continuity by varying the orientation of end elements. We find that (1) changing the angle of contour curvature decreased detection performance, while (2) end elements oriented in the direction (i.e., clockwise) of curvature facilitated contour detection regardless of the curvature angle of the contour. In Experiment 2 we further established that the relative effect of end—element orientation on contour detection was not only dependent on their orientation (collinear or cocircular), but also their spatial separation from the contour, and whether the contour shape was curved or not (i.e., C-shaped or S-shaped). Increasing the spatial separation of end-elements reduced contour detection performance regardless of their orientation or the contour shape. However, at small separations, cocircular end-elements facilitated the detection of C-shaped contours, but not S-shaped contours. The opposite result was observed for collinear end-elements, which improved the detection of S- shaped, but not C-shaped contours. These dissociative results confirmed that the visual system specifically codes contour curvature, but the association of contour elements occurs locally. Finally, we undertook an analysis of natural images that mapped contours with a constant angular change and determined the frequency of occurrence of end elements with different orientations. Analogous to our behavioral data, this image analysis revealed that the mapped end elements of constantly curved contours are likely to be oriented clockwise to the angle of curvature. Our findings indicate that the visual system is selectively sensitive to contours defined by constant curvature and that this might reflect the properties of curved contours in natural images.

Capacity to improve fine motor skills in Williams syndrome

BACKGROUND

Individuals with Williams syndrome (WS) are known to have difficulties in carrying out fine motor movements; however, a detailed behavioural profile of WS in this domain is still missing. It is also unknown how great the capacity to improve these skills with focused and extensive practice is.

METHOD

We studied initial performance and learning capacity in a sequential finger tapping (FT) task in WS and in typical development. Improvement in the FT task has been shown to be sleep dependent. WS subjects participating in the current study have also participated in earlier polysomnography studies, although not directly related to learning.

RESULTS

WS participants presented with great individual variability. In addition to generally poor initial performance, learning capacity was also greatly limited in WS. We found indications that reduced sleep efficiency might contribute to this limitation.

CONCLUSIONS

Estimating motor learning capacity and the depth of sleep disorder in a larger sample of WS individuals might reveal important relationships between sleep and learning, and contribute to efficient intervention methods improving skill acquisition in WS.

Effects of Spatial Frequency Similarity and Dissimilarity on Contour Integration

We examined the effects of spatial frequency similarity and dissimilarity on human contour integration under various conditions of uncertainty. Participants performed a temporal 2AFC contour detection task. Spatial frequency jitter up to 3.0 octaves was applied either to background elements, or to contour and background elements, or to none of both. Results converge on four major findings. (1) Contours defined by spatial frequency similarity alone are only scarcely visible, suggesting the absence of specialized cortical routines for shape detection based on spatial frequency similarity. (2) When orientation collinearity and spatial frequency similarity are combined along a contour, performance amplifies far beyond probability summation when compared to the fully heterogenous condition but only to a margin compatible with probability summation when compared to the fully homogenous case. (3) Psychometric functions are steeper but not shifted for homogenous contours in heterogenous backgrounds indicating an advantageous signal-to-noise ratio. The additional similarity cue therefore not so much improves contour detection performance but primarily reduces observer uncertainty about whether a potential candidate is a contour or just a false positive. (4) Contour integration is a broadband mechanism which is only moderately impaired by spatial frequency dissimilarity.

Characterizing synaptic protein development in human visual cortex enables alignment of synaptic age with rat visual cortex

Although many potential neuroplasticity based therapies have been developed in the lab, few have translated into established clinical treatments for human neurologic or neuropsychiatric diseases. Animal models, especially of the visual system, have shaped our understanding of neuroplasticity by characterizing the mechanisms that promote neural changes and defining timing of the sensitive period. The lack of knowledge about development of synaptic plasticity mechanisms in human cortex, and about alignment of synaptic age between animals and humans, has limited translation of neuroplasticity therapies. In this study, we quantified expression of a set of highly conserved pre- and post-synaptic proteins (Synapsin, Synaptophysin, PSD-95, Gephyrin) and found that synaptic development in human primary visual cortex (V1) continues into late childhood. Indeed, this is many years longer than suggested by neuroanatomical studies and points to a prolonged sensitive period for plasticity in human sensory cortex. In addition, during childhood we found waves of inter-individual variability that are different for the four proteins and include a stage during early development (<1 year) when only Gephyrin has high inter-individual variability. We also found that pre- and post-synaptic protein balances develop quickly, suggesting that maturation of certain synaptic functions happens within the 1 year or 2 of life. A multidimensional analysis (principle component analysis) showed that most of the variance was captured by the sum of the four synaptic proteins. We used that sum to compare development of human and rat visual cortex and identified a simple linear equation that provides robust alignment of synaptic age between humans and rats. Alignment of synaptic ages is important for age-appropriate targeting and effective translation of neuroplasticity therapies from the lab to the clinic.

Global dot integration in typically developing children and in Williams syndrome

Williams Syndrome (WS) is a neurodevelopmental disorder that results in deficits in visuospatial perception and cognition. The dorsal stream vulnerability hypothesis in WS predicts that visual motion processes are more susceptible to damage than visual form processes. We asked WS participants and typically developing children to detect the global structure Glass patterns, under "static" and "dynamic" conditions in order to evaluate this hypothesis. Sequentially presented Glass patterns are coined as dynamic because they induce illusory motion, which is modeled after the interaction between orientation (form) and direction (motion) mechanisms. If the dorsal stream vulnerability holds in WS participants, then they should process real and illusory motion atypically. However, results are consistent with the idea that form and motion integration mechanisms are functionally delayed or attenuated in WS. Form coherence thresholds for both static and dynamic Glass patterns in WS were similar to those of 4-5year old children, younger than what is predicted by mental age. Dynamic presentation of Glass patterns improved thresholds to the same degree as typical participants. Motion coherence thresholds in WS were similar to those of mental age matches. These data pose constraints on the dorsal vulnerability hypothesis, and refine our understanding of the relationship between form and motion processing in development.

Infusing Neuroscience into Teacher Professional Development

Bruer (1997) advocated connecting neuroscience and education indirectly through the intermediate discipline of psychology. We argue for a parallel route: the neurobiology of learning, and in particular the core concept of plasticity, have the potential to directly transform teacher preparation and professional development, and ultimately to affect how students think about their own learning. We present a case study of how the core concepts of neuroscience can be brought to in-service teachers - the BrainU workshops. We then discuss how neuroscience can be meaningfully integrated into pre-service teacher preparation, focusing on institutional and cultural barriers.

Does variation in neurodegenerative disease susceptibility and phenotype reflect cerebral differences at the network level?

Alzheimer's disease (AD) is 10-fold more frequent than Parkinson's disease (PD), which in turn is 10-fold more frequent than amyotrophic lateral sclerosis (ALS). The differences between these neurodegenerative diseases have been ascribed to a selective vulnerability of specific neuronal sub-types that then determine each disorder. However, there are non-neuronal cells that are ubiquitously and possibly primarily involved in all of them, and they share regulatory mechanisms through similar interneurons and, typically inhibitory, neurotransmitters. There is recognized clinical and neuropathological overlap between AD, PD and ALS, the best example being Guamanian Lytico-Bodig, but increasingly recognized in larger populations, e.g. carriers of C9orf72 hexanucleotide expansions. From early embryogenesis to adulthood, genetic and experience-dependent functional neural networks develop primarily in relation to the neocortex. From an evolutionary standpoint, cognition, memory, executive function, linguistics and fine motor function are most prominent in humans. It is concluded that neural networks, rather than specific neuronal sub-types defined regionally or by individual transmitters, underlie the marked differences between neurodegenerative disorders in terms of susceptibility and clinical features. This requires the continued development of strategies to study brain function in health and disease as the 'system', greater than the sum of its parts.

Perceptual learning in Williams syndrome: looking beyond averages

Williams Syndrome is a genetically determined neurodevelopmental disorder characterized by an uneven cognitive profile and surprisingly large neurobehavioral differences among individuals. Previous studies have already shown different forms of memory deficiencies and learning difficulties in WS. Here we studied the capacity of WS subjects to improve their performance in a basic visual task. We employed a contour integration paradigm that addresses occipital visual function, and analyzed the initial (i.e. baseline) and after-learning performance of WS individuals. Instead of pooling the very inhomogeneous results of WS subjects together, we evaluated individual performance by expressing it in terms of the deviation from the average performance of the group of typically developing subjects of similar age. This approach helped us to reveal information about the possible origins of poor performance of WS subjects in contour integration. Although the majority of WS individuals showed both reduced baseline and reduced learning performance, individual analysis also revealed a dissociation between baseline and learning capacity in several WS subjects. In spite of impaired initial contour integration performance, some WS individuals presented learning capacity comparable to learning in the typically developing population, and vice versa, poor learning was also observed in subjects with high initial performance levels. These data indicate a dissociation between factors determining initial performance and perceptual learning.