16849
The Specificity of Atypical Language Development in Infants at-Risk for ASD
Language delays and deficits in social communication are characteristic features of Autism Spectrum Disorder (ASD). Recent research has identified early-developing atypical patterns of hemispheric lateralization in response to language stimuli. However, it remains unclear whether atypical hemispheric lateralization is specific to ASD or whether it underlies non-syndrome-specific language delays. In order to examine the specificity of neurophysiological responses to language, we recruited three groups of infants: infants at high-risk for ASD by virtue of having a sibling diagnosed with the disorder, infants at normal-risk for ASD, and infants with non-syndromic craniosynostosis (NCS) and deformational plagiocephaly (DP). Infants with NCS and DP represent an ideal comparison group because these conditions have been associated with atypical language development but not with social communication deficits.
Objectives:
This study compared differences in hemispheric lateralization during a language processing task in in infants at high-risk for ASD relative to those with NCS or DP and infants at normal-risk for ASD. We analyzed the EEG signal in two separate ways: (a) event-related potentials (ERP) and (2) event-related linear coherence between frontal and temporo-parietal regions. These two measures were chosen to obtain information about both localized neural responses (ERP) and synchronized activity across larger networks (linear coherence).
Methods:
We collected data from: 13 infants high-risk for ASD, 20 normal-risk controls, and 23 infants with NCS or DP. EEGs were recorded with a 128 channel HydroCel GSN net during auditory presentations of phonemes. EEG data was analyzed to (a) extract ERPs evoked by phonemes (P150, a positive deflection over left and right anterior scalp between 100 and 300 ms), and (b) to compute linear coherence in the time-frequency domain between frontal and temporo-parietal intrahemispheric sites.
Results:
Preliminary analysis revealed a significant Group by Hemisphere interaction in the P150 (p = 0.036). Follow up t-tests revealed significant hemispheric differences in normal-risk infants (p = 0.043), but not in high-risk infants (p = 0.431) or infants with cranial abnormalities (p = 0.326). Prior analyses in a different sample of infants revealed that high-risk infants had overall reduced linear coherence between anterior and posterior sites, compared to normal-risk infants. We expect the patterns of lateralization to parallel the findings of our ERP data, suggesting that atypical language development is associated with lack of hemispheric lateralization. However, we expect our three groups to differ in overall coherence, as overall differences in synchronization might underlie broader deficits.
Conclusions:
Preliminary results show that non-syndrome specific atypical language development is associated with reduced hemispheric lateralization during language processing. We anticipate differences in lateralization to be associated primarily with language delays, whereas we expect overall differences in synchronization of large networks to be indicative of broader deficits. The presence of a non-ASD group with documented language delays will provide critical information regarding the specificity of atypical neural responses to language. Differences between infants at-risk for ASD and infants with cranial abnormalities may shed light on early-developing neural atypicalities that give rise to the communication deficits documented in ASD.