Backward and forward visual masking in schizophrenia and its relation to global motion and global form perception

AbstractThe ability to extract form information from a visual scene, for object recognition or figure–ground segregation, is a fundamental visual system function. Many studies of nonhuman primates have addressed the neural mechanisms involved in global form processing, but few have sought to demonstrate this ability behaviorally. In this study, we probed global visual processing in macaque monkeys (Macaca nemestrina) using classical Kanizsa illusory shapes as an assay of global form perception. We trained three monkeys on a “similarity match-to-sample” form discrimination task, first with complete forms embedded in fields of noncontour-inducing “pacman” elements. We then tested them with classic Kanizsa illusory shapes embedded in fields of randomly oriented elements. Two of the three subjects reached our criterion performance level of 80% correct or better on four of five illusory test conditions, demonstrating clear evidence of Kanizsa illusory form perception; the third subject mastered three of five conditions. Performance limits for illusory form discrimination were obtained by manipulating support ratio and by measuring threshold for discriminating “fat” and “thin” illusory squares. Our results indicate that macaque monkeys are capable of global form processing similarly to humans and that the perceptual mechanisms for “filling-in” contour gaps exist in macaques as they do in humans.

Download Full-text

Dorsal and Ventral Stream Function in Children With Developmental Coordination Disorder

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2021.703217 ◽

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.

Download Full-text