Neurophysiological mechanisms of auditory processing in children with Autism Spectrum Disorder: An MEG study
Although Autism Spectrum Disorder (ASD) is an umbrella of different disorders with different etiology and pathogenesis (Coleman & Gillberg, 2013), numerous studies have shown some neurobiological similarities across children with autism (e.g., Rubenstein & Merzenich, 2003). It can be explained in term that all genes associated with ASD are involved in synapse formation and regulation of excitation and inhibition balance in neural networks. Thus, imbalance between neuronal excitation and inhibition as well as ineffective neuronal connections are characterized most of the autistic brains.
The goal of this project is to investigate the process of excitation and inhibition in primary auditory cortex and to understand whether it is related to language impairments in children with ASD. We use magnetoencephalography (MEG) which is the most advanced neuroimaging technique having both good spatial and excellent temporal resolutions. In other words, we can register neurophysiological processes and to estimate their sources in the brain very precisely (co-registered with structural MRI).
We have developed two experiments to investigate the relationships between impairments in primary auditory cortex with language impairments in children with ASD.
1. We register the neurophysiological response of Heschl’s gyrus in primary auditory cortex to amplitude-modulated tones (2Hz in delta-band and 40Hz in gamma-band). According to Hickok and Poeppel’s theory (2007), low-frequency oscillations are relevant for accurate extraction of prosodic information from speech stream whereas high-frequency oscillations are relevant for coding discrete short items (phonemes). This experiment will show how autistic brain is processed different amplitude-modulated tones and how it is related to language impairment (the extent of language impairments is assessed with behavioral testing).
2. We investigate the process of sensory gating with classical paired-click paradigm, registering an early neurophysiological component P50m. In typically developing brain, there is a reduced response at about 50 ms after stimulus onset for the second identical click by cortical inhibitory mechanism. Some studies have shown the relationships between sensory gating and attention as well as non-verbal IQ in children with ASD (e.g., Orekhova et al., 2008). We investigate this process in association with language impairments in children with ASD because there is an evidence that sensory gating can be related to basic mechanisms of categorization.
In general, this project will help us to understand the degree of auditory processing impairment in children with autism and its relation to language impairment. Moreover, we will compare the extent of neurophysiological processing deficit in primary auditory cortex with computer morphometry data of the same brain region (grey matter thickness).
Arutiunian V. Talk «Neurophysiological mechanisms of language impairment in children with Autism Spectrum Disorder". Global Speech Forum, Moscow, 26-28 April, 2019.
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