Development of white matter tracts between and within the dorsal and ventral streams

The relation between neuroimaging and visual impairment in children and adolescents with cerebral palsy: A systematic review

OBJECTIVE

The structure-function relation between magnetic resonance imaging (MRI) and visual impairment (VI) in children with cerebral palsy (CP) has not been fully unravelled. The present systematic review aims to summarize the relation between brain lesions on MRI and VI in children and adolescents with CP.

METHODS

PubMed, Embase, Web of Science Core Collection, and Cochrane Database were systematically searched according to the PRISMA checklist. A total of 45 articles met the inclusion criteria.

RESULTS

White matter lesions were most frequently associated with VI. Only 25 studies described lesions within specific structures, mainly in the optic radiations. Only four studies reported on the thalamus. 8.4% of children with CP showed no brain abnormalities on MRI. Diffusion-weighted MRI studies showed that decreased structural connectivity in the optic radiations, superior longitudinal fasciculus, posterior limb of the internal capsule, and occipital lobe is associated with more severe VI.

CONCLUSIONS

All types of brain lesions lead to visual dysfunctions, arguing for a comprehensive visual assessment in all children with CP. Whereas white matter damage is a well-known contributor, the exact contribution of specific visual structures requires further investigation, to enable early prediction, detection, and intervention.

Selective short-term memory impairment for verbalizable visual objects in children with Developmental Language Disorder

BACKGROUND

Developmental language disorder (DLD) affects the ability to acquire and make use of native language. Possible underlying cognitive mechanisms are related to memory functions.

AIMS

The aim was examination of the relationship between visual short-term memory of objects as well as audiovisual short-term memory, and particular nonverbal and language abilities.

METHODS AND PROCEDURES

The study included 7-9-year-old children with DLD and matched control group. Participants completed the Language Development Test, the Stanford-Binet IQ scale (SB5), and two short-term memory tasks: immediate recall of the visually presented pictograms and immediate recall of audiovisually presented sequences of syllables.

OUTCOMES AND RESULTS

The results revealed diminished levels of short-term visual memory for objects as well as audiovisual memory in children with DLD. However, there were no group differences in the control task of WM.

CONCLUSIONS AND IMPLICATIONS

Results supported the idea of diminished abilities in children with DLD to perform mental operations on verbalizable visual objects. Importantly non-verbal working memory ability, which cannot easily be supported by verbal representations, is at typical levels. This suggests that verbalization ability should be taken into account in the assessment of seemingly non-verbal cognitive functions among children with DLD.

Reduced perception-action dissociation in children with amblyopia

The functional distinction between vision-for-perception and vision-for-action is a key aspect of understanding the primate visual system. While this dissociation has been well-established in adulthood, its development and dependence on typical visual experience remain unclear. To address these questions, we examined two groups of children: typically developed children and those with amblyopia, who presumably have a sub-optimal visual experience. The Ponzo illusion, known to impact perception but not visuomotor behaviors across age groups, was employed to assess the extent of dissociation. Participants engaged in two tasks involving the Ponzo illusion: a grasping task (vision-for-action) and a manual estimation task (vision-for-perception), with objects placed on the "close" and "far" surfaces of the illusion. Typically developed children displayed grasping movements that were unaffected by the illusion, as their grasping apertures were scaled based on object size, independent of its location. In contrast, children with amblyopia exhibited a clear susceptibility to the illusion, showing larger apertures for objects placed on the 'far' surface of the illusion, and smaller apertures for objects placed on the 'close' surface. Interestingly, both groups of children demonstrated similar susceptibility to the illusion during the perceptual task, with objects placed on the far surface being perceived as longer compared to objects placed on the close surface. These findings shed light on the impact of atypical visual development on the emergence of the dissociation between perception and action, highlighting the crucial role of typical visual experience in establishing this distinction.

Associative white matter tracts selectively predict sensorimotor learning

Human learning is a complex phenomenon that varies greatly among individuals and is related to the microstructure of major white matter tracts in several learning domains, yet the impact of the existing myelination of white matter tracts on future learning outcomes remains unclear. We employed a machine-learning model selection framework to evaluate whether existing microstructure might predict individual differences in the potential for learning a sensorimotor task, and further, if the mapping between the microstructure of major white matter tracts and learning was selective for learning outcomes. We used diffusion tractography to measure the mean fractional anisotropy (FA) of white matter tracts in 60 adult participants who then underwent training and subsequent testing to evaluate learning. During training, participants practiced drawing a set of 40 novel symbols repeatedly using a digital writing tablet. We measured drawing learning as the slope of draw duration over the practice session and visual recognition learning as the performance accuracy in an old/new 2-AFC recognition task. Results demonstrated that the microstructure of major white matter tracts selectively predicted learning outcomes, with left hemisphere pArc and SLF 3 tracts predicting drawing learning and the left hemisphere MDLFspl predicting visual recognition learning. These results were replicated in a repeat, held-out data set and supported with complementary analyses. Overall, results suggest that individual differences in the microstructure of human white matter tracts may be selectively related to future learning outcomes and open avenues of inquiry concerning the impact of existing tract myelination in the potential for learning.

Significance statement

A selective mapping between tract microstructure and future learning has been demonstrated in the murine model and, to our knowledge, has not yet been demonstrated in humans. We employed a data-driven approach that identified only two tracts, the two most posterior segments of the arcuate fasciculus in the left hemisphere, to predict learning a sensorimotor task (drawing symbols) and this prediction model did not transfer to other learning outcomes (visual symbol recognition). Results suggest that individual differences in learning may be selectively related to the tissue properties of major white matter tracts in the human brain.

White matter connections of high-level visual areas predict cytoarchitecture better than category-selectivity in childhood, but not adulthood

Ventral temporal cortex (VTC) consists of high-level visual regions that are arranged in consistent anatomical locations across individuals. This consistency has led to several hypotheses about the factors that constrain the functional organization of VTC. A prevailing theory is that white matter connections influence the organization of VTC, however, the nature of this constraint is unclear. Here, we test 2 hypotheses: (1) white matter tracts are specific for each category or (2) white matter tracts are specific to cytoarchitectonic areas of VTC. To test these hypotheses, we used diffusion magnetic resonance imaging to identify white matter tracts and functional magnetic resonance imaging to identify category-selective regions in VTC in children and adults. We find that in childhood, white matter connections are linked to cytoarchitecture rather than category-selectivity. In adulthood, however, white matter connections are linked to both cytoarchitecture and category-selectivity. These results suggest a rethinking of the view that category-selective regions in VTC have category-specific white matter connections early in development. Instead, these findings suggest that the neural hardware underlying the processing of categorical stimuli may be more domain-general than previously thought, particularly in childhood.