Neural foundations of phonological processing deficit in children with Autism Spectrum Disorders
Autism Spectrum Disorders (ASD) are a continuum of neurodevelopmental disorders characterized by impairments in social interaction, communication and repetitive / stereotype behavior. It is known that ASD is a heterogeneous disorder which is caused by different genetic and neurobiological factors.
Speech delay or impairments in language is one of the main “red flags” in ASD. However, we do not know until now what primary language problems cause later speech and language deficits in children with ASD.
The goal of the present project is to assess the phonological processing deficit in children with ASD because we assume that impairments in different linguistic levels (lexical, grammatical, morphological, etc.) can be related with primary phonological deficit. This study consists of both behavioral assessments (clinical language tests) and neurobiological research (diffusion-tensor MRI and magnetoencephalography).
- Behavioral / clinical assessment. All children are involved in behavioral assessment with different standardized language and phonological tests developed at the Center for Language and Brain. These tests will determine a language proficiency of a child, including the ability of phonological processing.
- Diffusion tensor imaging (DTI) and tractography. Here, 4-to-6-year-old low-functioning children with ASD are involved in MRI study where we perform a virtual dissection of the arcuate fasciculus (AF) in both hemispheres (Figure 1). It is known that AF is related to phonological processing and it has left lateralization. The general goals of this study are to correlated the phonological behavior with DTI metrics of AF and to assess its lateralization in children with ASD.
Figure 1. Arcuate fasciculus of the left hemisphere
- Magnetoencephalography. We use magnetoencephalography (MEG) for measuring neural activity during phonological processing in 7-to-11-year-old children with ASD, children with Fragile X syndrome, children with Down syndrome and typically developing children. A whole-head 306 sensors MEG is a noninvasive and ultra modern method for direct measuring of neural activity which has both an excellent temporal and good spatial resolution (Figure 2).
Figure 2. Magnetoencephalography
The general goal of this study is to understand at which frequency band the problem is in children with ASD during phonological processing. It is known that different brain oscillations are associated with different types of phonological processing: lower frequencies are corresponded to syllables and stress patterns whereas high frequencies are corresponded to phonemes. We record MEG during passive listening a white noise at different frequency rates – 2 Hz (delta), 4 Hz (theta), 20 Hz (beta) and 40 Hz (gamma). We will do phase-locking analysis to understand how autistic brains process different types of phonological information.
In this project, 4-to-6-year-old low-functioning children with ASD, 7-to-11-year-old functioning children with ASD, children with Fragile X syndrome, children with Down syndrome and typically developing children are involved.
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