scholarly journals Locating 'dorsal stream vulnerability': high-density global motion and form coherence VEPs related to MRI in infants born very preterm

2011 ◽  
Vol 11 (11) ◽  
pp. 457-457 ◽  
Author(s):  
J. Atkinson ◽  
D. Birtles ◽  
S. Anker ◽  
J. Wattam-Bell ◽  
M. Rutherford ◽  
...  
Keyword(s):  
Dorsal Stream ◽  
High Density ◽  
Global Motion ◽  
Very Preterm ◽  
Form Coherence

scholarly journals Dorsal and Ventral Stream Function in Children With Developmental Coordination Disorder

2021 ◽  
Vol 15 ◽  
Author(s):  
Serena Micheletti ◽  
Fleur Corbett ◽  
Janette Atkinson ◽  
Oliver Braddick ◽  
Paola Mattei ◽  
...  
Keyword(s):  
Developmental Coordination Disorder ◽  
Motor Impairment ◽  
Dorsal Stream ◽  
Ventral Stream ◽  
Global Motion ◽  
Motion Sensitivity ◽  
Global Form ◽  
Global Coherence ◽  
Static Form ◽  
Coordination Disorder

Dorsal stream cortical networks underpin a cluster of visuomotor, visuospatial, and visual attention functions. Sensitivity to global coherence of motion and static form is considered a signature of visual cortical processing in the dorsal stream (motion) relative to the ventral stream (form). Poorer sensitivity to global motion compared to global static form has been found across a diverse range of neurodevelopmental disorders, suggesting a “dorsal stream vulnerability.” However, previous studies of global coherence sensitivity in Developmental Coordination Disorder (DCD) have shown conflicting findings. We examined two groups totalling 102 children with DCD (age 5–12 years), using the “Ball in the Grass” psychophysical test to compare sensitivity to global motion and global static form. Motor impairment was measured using the Movement-ABC (M-ABC). Global coherence sensitivity was compared with a typically developing control group (N = 69) in the same age range. Children with DCD showed impaired sensitivity to global motion (p = 0.002), but not global form (p = 0.695), compared to controls. Within the DCD group, motor impairment showed a significant linear relationship with global form sensitivity (p < 0.001). There was also a significant quadratic relationship between motor impairment and global motion sensitivity (p = 0.046), where poorer global motion sensitivity was only apparent with greater motor impairment. We suggest that two distinct visually related components, associated with global form and global motion sensitivity, contribute to DCD differentially over the range of severity of the disorder. Possible neural circuitry underlying these relationships is discussed.

scholarly journals Global motion detection and censoring in high‐density diffuse optical tomography

2020 ◽  
Vol 41 (14) ◽  
pp. 4093-4112 ◽  
Author(s):  
Arefeh Sherafati ◽  
Abraham Z. Snyder ◽  
Adam T. Eggebrecht ◽  
Karla M. Bergonzi ◽  
Tracy M. Burns‐Yocum ◽  
...  
Keyword(s):  
Motion Detection ◽  
Optical Tomography ◽  
Diffuse Optical Tomography ◽  
High Density ◽  
Global Motion

scholarly journals High-density VEP measures of global form and motion processing in infants born very preterm

2010 ◽  
Vol 8 (6) ◽  
pp. 422-422
Author(s):  
A. Janette ◽  
B. Dee ◽  
A. Shirley ◽  
B. Oliver ◽  
R. Mary ◽  
...  
Keyword(s):  
High Density ◽  
Motion Processing ◽  
Very Preterm ◽  
Global Form

scholarly journals Global Visual Motion Sensitivity: Associations with Parietal Area and Children's Mathematical Cognition

2016 ◽  
Vol 28 (12) ◽  
pp. 1897-1908 ◽  
Author(s):  
Oliver Braddick ◽  
Janette Atkinson ◽  
Erik Newman ◽  
Natacha Akshoomoff ◽  
Joshua M. Kuperman ◽  
...  
Keyword(s):  
Individual Differences ◽  
Brain Development ◽  
Numerical Cognition ◽  
Visual Motion ◽  
Dorsal Stream ◽  
Motion Processing ◽  
Intraparietal Sulcus ◽  
Global Motion ◽  
Visuomotor Integration ◽  
Motion Sensitivity

Sensitivity to global visual motion has been proposed as a signature of brain development, related to the dorsal rather than ventral cortical stream. Thresholds for global motion have been found to be elevated more than for global static form in many developmental disorders, leading to the idea of “dorsal stream vulnerability.” Here we explore the association of global motion thresholds with individual differences in children's brain development, in a group of typically developing 5- to 12-year-olds. Good performance was associated with a relative increase in parietal lobe surface area, most strongly around the intraparietal sulcus and decrease in occipital area. In line with the involvement of intraparietal sulcus, areas in visuospatial and numerical cognition, we also found that global motion performance was correlated with tests of visuomotor integration and numerical skills. Individual differences in global form detection showed none of these anatomical or cognitive correlations. This suggests that the correlations with motion sensitivity are unlikely to reflect general perceptual or attentional abilities required for both form and motion. We conclude that individual developmental variations in global motion processing are not linked to greater area in the extrastriate visual areas, which initially process such motion, but in the parietal systems that make decisions based on this information. The overlap with visuospatial and numerical abilities may indicate the anatomical substrate of the “dorsal stream vulnerability” proposed as characterizing neurodevelopmental disorders.

Visual Development

2017 ◽  
Author(s):  
Janette Atkinson
Keyword(s):  
Developmental Disorders ◽  
Numerical Cognition ◽  
Dorsal Stream ◽  
Ventral Stream ◽  
Visual Development ◽  
Motion Processing ◽  
Global Motion ◽  
Visual Responses ◽  
Motion Sensitivity ◽  
Static Form

Human visual development is a complex dynamic psychological/neurobiological process, being part of the developing systems for cognition, action, and attention. This article reviews current knowledge and methods of study of human visual development in infancy and childhood, in relation to typical early visual brain development, and how it can change in developmental disorders, both acquired (e.g., related to at-risk births) and genetic disorders. The newborn infant starts life with a functioning subcortical visual system which controls newborn orienting to nearby high contrast objects and faces. Although visual cortex may be active from birth, its characteristic stimulus selectivity and control of visual responses is generally seen to emerge around six to twelve weeks after birth. By age six months the infant has adequate acuity and contrast sensitivity in nearby space, and operating cortical mechanisms for discriminating colors, shapes, faces, movement, stereo depth, and distance of objects, as well as the ability to focus and shift attention between objects of interest. This may include both feedforward and feedback pathways between cortical areas and between cortical and subcortical areas. Two cortical streams start to develop and become interlinked, the dorsal stream underpinning motion, spatial perception and actions, and the ventral stream for recognition of objects and faces. The neural systems developing control and planning of actions include those for directed eye movements, reaching and grasping, and the beginnings of locomotion, with these action systems being integrated into the other developing subcortical and cortical visual networks by one year of age. Analysis of global static form (pattern) and global motion processing allows the development of dorsal and ventral streams to be monitored from infancy through childhood. The development of attention, visuomotor control and spatial cognition in the first years show aspects of function related to the developing dorsal stream, and their integration with the ventral stream. The milestones of typical visual development can be used to characterize visual and visuo-cognitive disorders early in life, such as in infants with perinatal brain injuries and those born very prematurely. The concept of “dorsal stream vulnerability” is outlined. It was initially based on deficits in global motion sensitivity relative to static form sensitivity, but can be extended to the planning and execution of visuomotor actions and problems of attention, together with visuospatial and numerical cognition. These problems are found in the phenotype of children with both genetic developmental disorders (e.g., Williams syndrome, autism, fragile-X, and dyslexia), and in acquired developmental disorders related to very preterm birth, or in children with abnormal visual input such as congenital cataract, refractive errors, or amblyopia. However, there are subtle differences in the manifestation of these disorders which may also vary considerably across individuals. Development in these clinical conditions illustrates the early, but limited, plasticity of visual brain mechanisms, and provides a challenge for the future in designing successful intervention and treatment.

Planar defects in ordered (Ga,In)P

1988 ◽  
Vol 46 ◽  
pp. 902-903
Author(s):  
S. McKernan ◽  
C. B. Carter ◽  
D. Bour ◽  
J. R. Shealy
Keyword(s):  
Electron Diffraction ◽  
Vapor Phase ◽  
Growth Direction ◽  
High Density ◽  
Ordered Structure ◽  
Planar Defects ◽  
Diffraction Patterns ◽  
Ternary Semiconductors ◽  
Anion Species ◽  
Metallic Vapor

The growth of ternary III-V semiconductors by organo-metallic vapor phase epitaxy (OMVPE) is widely practiced. It has been generally assumed that the resulting structure is the same as that of the corresponding binary semiconductors, but with the two different cation or anion species randomly distributed on their appropriate sublattice sites. Recently several different ternary semiconductors including AlxGa1-xAs, Gaxln-1-xAs and Gaxln1-xP1-6 have been observed in ordered states. A common feature of these ordered compounds is that they contain a relatively high density of defects. This is evident in electron diffraction patterns from these materials where streaks, which are typically parallel to the growth direction, are associated with the extra reflections arising from the ordering. However, where the (Ga,ln)P epilayer is reasonably well ordered the streaking is extremely faint, and the intensity of the ordered spot at 1/2(111) is much greater than that at 1/2(111). In these cases it is possible to image relatively clearly many of the defects found in the ordered structure.

Quantitative defect studies in semiconductor TEM samples prepared by low angle ion milling

1995 ◽  
Vol 53 ◽  
pp. 512-513
Author(s):  
L. Mulestagno ◽  
J.C. Holzer ◽  
P. Fraundorf
Keyword(s):  
Sample Preparation ◽  
Milling Time ◽  
High Density ◽  
Low Density ◽  
Ion Milling ◽  
High Quality ◽  
Variable Angle ◽  
Major Disadvantage ◽  
Induced Defects

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).

Using the scanning electron microscope for failure analysis of high density magnetic media

1987 ◽  
Vol 45 ◽  
pp. 392-393
Author(s):  
Evelyn R. Ackerman ◽  
Gary D. Burnett
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Failure Analysis ◽  
High Density ◽  
Magnetic Media ◽  
Specific Data ◽  
Retrieval Systems ◽  
Operating Environments ◽  
The Media ◽  
Scanning Electron

Advancements in state of the art high density Head/Disk retrieval systems has increased the demand for sophisticated failure analysis methods. From 1968 to 1974 the emphasis was on the number of tracks per inch. (TPI) ranging from 100 to 400 as summarized in Table 1. This emphasis shifted with the increase in densities to include the number of bits per inch (BPI). A bit is formed by magnetizing the Fe203 particles of the media in one direction and allowing magnetic heads to recognize specific data patterns. From 1977 to 1986 the tracks per inch increased from 470 to 1400 corresponding to an increase from 6300 to 10,800 bits per inch respectively. Due to the reduction in the bit and track sizes, build and operating environments of systems have become critical factors in media reliability.Using the Ferrofluid pattern developing technique, the scanning electron microscope can be a valuable diagnostic tool in the examination of failure sites on disks.

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