Defining the female protective effect in infants with ASD
Background: Phelan-McDermid syndrome (PMS) occurs as a result of a chromosomal abnormality, most frequently
deletion, in the long arm of chromosome 22, involving the SHANK3 gene. Our goal was to prospectively assess the
neurological phenotype in this syndrome.
METHODS: Twenty-nine participants were recruited from ongoing studies in PMS at the Seaver Autism Center. They
had a structured, uniform neurological examination performed by a pediatric neurologist (Y.F.). Abnormal findings
were graded as mild, moderate or severe. In addition, reports of seizures, magnetic resonance imaging (MRI) and
electroencephalograms (EEG) were reviewed. We calculated the frequency and severity of neurological
abnormalities, as well as correlations between items on the neurological examination and items on the Mullen Scales
of Early Learning and on the Vineland Adaptive Behavioral Scales (VABS).
RESULTS: Hypotonia, abnormal gait, fine motor coordination deficits, and expressive and receptive language delays
were present in all participants. Attention deficits were present in 96% (severe in 62%), and abnormal visual tracking
was present in 86%. A history of seizures was obtained in 44.8% of participants but 46.1% of these were febrile only.
Of the 13 EEG reports available for review – 69.2% were abnormal- with epileptic features present in 53.8%.
Abnormalities were present in 62.5% of MRI reports. Correlations were found between neurological abnormalities
and scores on the Mullen and Vineland Scales.
CONCLUSIONS: Neurological abnormalities are very common in PMS and are correlated with measures of cognitive
and adaptive functioning. The neurological examination may be used for clinical diagnosis, identification of PMS
phenotypes, and, in the future, for evaluation of therapy.
Background: Autism spectrum disorder (ASD) is associated with impaired face processing. The N170 event-related potential (ERP) has been considered a promising neural marker of this impairment. However, no quantitative review to date has integrated the literature to assess whether the N170 response to faces in individuals with ASD differs from that of typically developing (TD) individuals.
Methods: This meta-analysis examined the corpus of literature investigating difference in N170 response to faces in individuals with ASD and without ASD. Data from 23 studies (NASD = 374, NTD = 359) were reviewed. Meta-analysis was used to examine the effect size of the difference in N170 latency and amplitude among individuals with ASD and without ASD. Analyses were also conducted examining hemispheric differences, potential moderators, and publication bias.
Results: On average, N170 latencies to faces were delayed in individuals with ASD, but amplitudes did not differ for individuals with ASD and TD individuals. Moderator analyses revealed that N170 amplitudes were smaller in magnitude in the ASD participants relative to the TD participants in adult samples and in those with higher cognitive ability. However, effects differed as a function of hemisphere of recording. No evidence of publication bias was found.
Conclusions: Atypicality of N170-particularly latency-to faces appears to be a specific biomarker of social-communicative dysfunction in ASD and may relate to differential developmental experiences and use of compensatory cognitive mechanisms. Future research should examine phenotypic differences that contribute to N170 heterogeneity, as well as specificity of N170 differences in ASD versus non-ASD clinical populations, and N170 malleability with treatment.
Keywords: Autism spectrum disorder (ASD); Electroencephalography (EEG); Event-related potential (ERP); Face processing; Meta-analysis; N170.
The parts of the body that are used to produce and perceive signed languages (the hands, face, and visual system) differ from those used to produce and perceive spoken languages (the vocal tract and auditory system). In this paper we address two factors that have important consequences for sign language acquisition. First, there are three types of lexical signs: one-handed, two-handed symmetrical, and two-handed asymmetrical. Natural variation in hand dominance in the population leads to varied input to children learning sign. Children must learn that signs are not specified for the right or left hand but for dominant and non-dominant. Second, we posit that children have at least four imitation strategies available for imitating signs: anatomical (Activate the same muscles as the sign model), which could lead learners to inappropriately use their non-dominant hand; mirroring (Produce a mirror image of the modeled sign), which could lead learners to produce lateral movement reversal errors or to use the non-dominant hand; visual matching (Reproduce what you see from your perspective), which could lead learners to produce inward-outward movement and palm orientation reversals; and reversing (Reproduce what the sign model would see from his/her perspective). This last strategy is the only one that always yields correct phonological forms in signed languages. To test our hypotheses, we turn to evidence from typical and atypical hearing and deaf children as well as from typical adults; the data come from studies of both sign acquisition and gesture imitation. Specifically, we posit that all children initially use a visual matching strategy but typical children switch to a mirroring strategy sometime in the second year of life; typical adults tend to use a mirroring strategy in learning signs and imitating gestures. By contrast, children and adults with autism spectrum disorder (ASD) appear to use the visual matching strategy well into childhood or even adulthood. Finally, we present evidence that sign language exposure changes how adults imitate gestures, switching from a mirroring strategy to the correct reversal strategy. These four strategies for imitation do not exist in speech and as such constitute a unique problem for research in language acquisition.
Keywords: American Sign Language (ASL); Autism Spectrum Disorders (ASD); imitation; language acquisition; sign language; visual perspective-taking.