25689
Sensory Perception and Lexical-Semantic Processing in Minimally Verbal/Non-Verbal Children with ASD and Typical Controls Assessed Via Dense-Array EEG
We examined electrocortical activity associated with sensory perception (visual and auditory) and lexical-semantic processing in nonverbal (NV) or minimally verbal (MV) children with Autism Spectrum Disorder (ASD). Studies that have examined the neural correlates of higher-level linguistic processing in this population are rare. Specifically, there is no agreement on whether NV/MV ASD children as a group perceive and comprehend incoming linguistic input and whether speech, if perceived, is processed in a manner comparable to that of typically developing children. However, this is far from a homogenous group and our research, as well as that from other labs, suggests much individual variation across cognitive, social and receptive language domains. A key challenge in assessing this population is developing approaches to evaluating linguistic and cognitive abilities that do not confound linguistic performance with difficulties meeting task demands.
Objectives:
The purpose of this study was to use dense-array electroencepahalography (EEG) to examine the topography and time course of sensory/perceptual and higher-order linguistic skills in NV/MV children with ASD, and to compare their cortical responses and processing profiles to related visual and auditory input with that of typically developing children.
Methods:
Event related potentials (ERPs) of 10 NV/MV children with ASD and 10 neurotypical children (age range 4-7 years) were recorded during a passive picture-word matching paradigm. Still pictures of animals or inanimate objects were visually presented on a computer monitor while a word that either matched or mismatched the picture was auditorily presented. The specific paradigm used allowed us to investigate the entire pattern of information processing, from very early sensory perception (for both visual and auditory processing) through to lexical-semantic processing.
Results:
Atypical ERP responses were evident at all levels of processing in children with NV/MV ASD. Basic perceptual processing of visual and auditory stimuli was found to be significantly delayed but similar in amplitude and topography to control children. More significant differences were seen between children with ASD and typically developing children at the lexical-semantic level, suggesting more compromised higher order processes. Individual level analyses revealed that a reliable N400 component in response to the mismatch condition was detected in five of the ASD children and eight of the neurotypical children.
Conclusions:
These results suggest that although basic perception is relatively preserved in NV/MV children with ASD, higher levels of processing are impaired. However, we were also able to examine individual processing profiles, an important step in using such information to guide intervention. Thus, these studies represent a significant step towards developing a functional neurolinguistic assessment for this difficult-to-test population. The findings also challenge the notion that being nonverbal (i.e. “no spoken language”) implies an absence of language comprehension. In some individuals that may indeed be true, however, we have demonstrated that at least a subset of nonverbal ASD children may possess higher-level language processing skills than is evident from standardized testing procedures.