key components of Autism Spectrum Disorder (ASD). Event related brain
potentials (ERPs) have been shown to be sensitive measures of
differences in speech processing abilities of 3 year olds with typical
development (TD) and ASD (Kuhl, et al., 2005). ERP measures of word
processing have also been related to differences in language abilities
in TD toddlers (Mills, et al., 1997).
Objectives: Our goals were to use ERP measures of word processing in a
longitudinal study to (1) investigate differences in patterns of ERP
response to words by TD children and children with ASD; (2) study the
relationship between ERP measures and later outcomes in children with
ASD (cognitive, language and social domains); and (3) examine the
development of the ERP response over time in TD children and children
with ASD.
Methods: Participants were children with ASD and age-matched TD
controls. ERPs and behavioral measures of cognitive, language, and
social function were collected at 18-30 months (T1) and again at 4 years
(T2). ERPs were recorded using 22 channel electrocaps with standard
10/20 arrangement. Stimuli consisted of 3 word types: words known to the
child, unknown words and backwards words (known words reversed). Parents
of participants signed an informed, University IRB approved consent form
prior to study participation.
Results: Significant differences in patterns of ERP latency and amplitude
were observed at T1 and T2 between TD's and children
with ASD, and between high functioning (HF) and low functioning (LF)
children with ASD. In general TD children show a more focused response
to known and unknown words, with a differential left temporal response
to known and unknown words at T1. They exhibited a significantly
smaller, less negative response to words at bilateral temporal (compared
to frontal and parietal), at T2. Children with ASD show a broadly
distributed response across electrode sites for known and unknown words
at both ages. HF children with autism exhibited a more localized
response to words, similar to that of TD controls. LF children with ASD
had more diffuse patterns of response. In addition, T1 ERP measures from
children with ASD were significantly correlated with measures of
language, IQ and severity of autism symptoms collected two years later
at T2: mean amplitudes and peak latencies of known words at T1 predicted
behavior scores at T2 (Coffey-Corina, et al., 2008).
Conclusions: In general, HF children with ASD exhibited more localized
ERP response, similar to TD controls. LF children with ASD had more
diffuse patterns of response. Significant predictive correlations were
obtained between ERPs to known words and various measures of language,
cognition/adaptation, and severity of autism symptoms obtained 2 years
after ERP testing. Further research using brain measures of speech
processing in children with ASD and TD controls is important to theory
building and to understanding the nature of the relationship between the
linguistic and social deficits which are characteristic of autism, and
may have implications for diagnosis and treatment in children with
developmental disabilities that involve language.