Spatial contrast sensitivity in adolescents with autism spectrum disorders

Adolescents with autism spectrum disorders (ASD) and typically developing (TD) controls underwent a rigorous psychophysical assessment that measured contrast sensitivity to seven spatial frequencies (0.5-20 cycles/degree). A contrast sensitivity function (CSF) was then fitted for each participant, from which four measures were obtained: visual acuity, peak spatial frequency, peak contrast sensitivity, and contrast sensitivity at a low spatial frequency. There were no group differences on any of the four CSF measures, indicating no differential spatial frequency processing in ASD. Although it has been suggested that detail-oriented visual perception in individuals with ASD may be a result of differential sensitivities to low versus high spatial frequencies, the current study finds no evidence to support this hypothesis

Effects of gestational length, gender, postnatal age, and birth order on visual contrast sensitivity in infants

To investigate effects of visual experience versus preprogrammed mechanisms on visual development, we used multiple regression analysis to determine the extent to which a variety of variables (that differ in the extent to which they are tied to visual experience) predict luminance and chromatic (red/green) contrast sensitivity (CS), which are mediated by the magnocellular (M) and parvocellular (P) subcortical pathways, respectively. Our variables included gestational length (GL), birth weight (BW), gender, postnatal age (PNA), and birth order (BO). Two-month-olds (n = 60) and 6-month-olds (n = 122) were tested. Results revealed that (1) at 2 months, infants with longer GL have higher luminance CS; (2) at both ages, CS significantly increases over a ~21-day range of PNA, but this effect is stronger in 2- than 6-month-olds and stronger for chromatic than luminance CS; (3) at 2 months, boys have higher luminance CS than girls; and (4) at 2 months, firstborn infants have higher CS, while at 6 months, non-firstborn infants have higher CS. The results for PNA/GL are consistent with the possibility that P pathway development is more influenced by variables tied to visual experience (PNA), while M pathway development is more influenced by variables unrelated to visual experience (GL). Other variables, including prenatal environment, are also discussed

Atypical Face Versus Object Processing and Hemispheric Asymmetries in 10-Month-Old Infants at Risk for Autism

BACKGROUND: Previous studies have documented atypicalities in face/object processing in children and adults with autism spectrum disorders (ASD). To investigate whether such atypicalities may reflect a genetically-mediated risk factor present early in development, we measured face/object processing in 10-month-old “High-Risk” infants, who carry some of the genes associated with ASD because they have an older sibling diagnosed with the disorder. METHODS: We employed event related potentials (ERPs) to measure cortical responses to pictures of faces and objects, the objects being pictures of toys. Latencies and amplitudes of four ERP components (P100, N290, P400 and Nc) were compared between 20 High-Risk infants and 20 Low-Risk controls (infants with no family history of ASD). RESULTS: Responses to faces vs. objects differed between High- and Low-Risk infants, for the latencies of the N290 and P400. Differences were driven by faster responses to faces than objects in Low-Risk, but not High-Risk, infants (P400), and conversely, faster responses to objects than faces in High-Risk, but not Low-Risk, infants (N290). And, object responses were faster in High-Risk than Low-Risk infants (both N290 and P400). Left vs. right hemisphere responses also differed between High- and Low-Risk infants, for the amplitudes of the P100, N290 and P400; collapsed across faces/objects, Low-Risk, but not High-Risk, infants exhibited hemisphere asymmetries. CONCLUSIONS: Genetic risk for ASD is associated with atypical face vs. object processing, and an atypical lack of hemispheric asymmetry, early in life. These atypicalities might contribute to development of the disorder

Complete sparing of high-contrast color input to motion perception in cortical color blindness

It is widely held that color and motion are processed by separate parallel pathways in the visual system, but this view is difficult to reconcile with the fact that motion can be detected in equiluminant stimuli that are defined by color alone. To examine the relationship between color and motion, we tested three patients who had lost their color vision following cortical damage (central achromatopsia). Despite their profound loss in the subjective experience of color and their inability to detect the motion of faint colors, all three subjects showed surprisingly strong responses to high-contrast, moving color stimuli — equal in all respects to the performance of subjects with normal color vision. The pathway from opponent-color detectors in the retina to the motion analysis areas must therefore be independent of the damaged color centers in the occipitotemporal area. It is probably also independent of the motion analysis area MT/V5, because the contribution of color to motion detection in these patients is much stronger than the color response of monkey area MT