Abstract
Similar behavioral deficits are shared between individuals with autism spectrum disorders (ASD) and their first-degree relatives, such as impaired face memory, object recognition, and some language aspects. Functional neuroimaging studies have reported abnormalities in ASD in at least one brain area implicated in those functions, the fusiform gyrus (FG). High frequency oscillations have also been described as abnormal in ASD in a separate line of research. The present study examined whether low- and high-frequency oscillatory power, localized in part to FG and other language-related regions, differs in ASD subjects and first-degree relatives. Twelve individuals with ASD, 16 parents of children with ASD, and 35 healthy controls participated in a picture-naming task using magnetoencephalography (MEG) to assess oscillatory power and connectivity. Relative to controls, we observed reduced evoked high-gamma activity in the right superior temporal gyrus (STG) and reduced high-beta/low-gamma evoked power in the left inferior frontal gyrus (IFG) in the ASD group. Finally, reductions in phase-locked beta-band were also seen in the ASD group relative to controls, especially in the occipital lobes (OCC). First degree relatives, in contrast, exhibited higher high-gamma band power in the left STG compared with controls, as well as increased high-beta/low-gamma evoked power in the left FG. In the left hemisphere, beta- and gamma-band functional connectivity between the IFG and FG and between STG and OCC were higher in the autism group than in controls. This suggests that, contrary to what has been previously described, reduced connectivity is not observed across all scales of observation in autism. The lack of behavioral correlation for the findings warrants some caution in interpreting the relevance of such changes for language function in ASD. Our findings in parents implicates the gamma- and beta-band ranges as potential compensatory phenomena in autism relatives.
Highlights
High-frequency brain activities have a central role in various normal functions (Buzsaki and Draguhn, 2004), including sensory binding (Rodriguez et al, 1999), temporal regulation of neuronal activity during synaptic plasticity (Traub et al, 1998), memory processing (Fell et al, 2001), and large-scale integration (Varela et al, 2001)
We focused on the fusiform gyrus (FG), the inferior frontal gyrus, the superior temporal gyrus (STG), and the occipital lobe (OCC) for further ROI-based analyses for three reasons: (1) their relevance to language function, (2) the engagement of visual structures in this specific task, and (3) leadfield correlation is high among closely spaced regions and induces artificial correlation in source waveforms derived from such locations
TIME-FREQUENCY RESULTS Fusiform gyrus For the left FG, the evoked power was significantly higher in the parents of a child with ASD (PASD) group, relative to the controls, for high beta/low gammaband activity centered around 35 Hz and from around 580–700 ms post-stimulus onset (Figure 2)
Summary
High-frequency brain activities have a central role in various normal functions (Buzsaki and Draguhn, 2004), including sensory binding (Rodriguez et al, 1999), temporal regulation of neuronal activity during synaptic plasticity (Traub et al, 1998), memory processing (Fell et al, 2001), and large-scale integration (Varela et al, 2001). Several suggestions have been proposed to define the role of gamma-band oscillations (30 Hz and higher) as a correlate of auditory awareness (Makeig and Jung, 1996; Yordanova et al, 2002) or encoding mental representations (Tallon-Baudry and Bertrand, 1999). In autism spectrum disorders (ASD), impairments of gamma oscillations have been previously described in auditory (Wilson et al, 2007; Gandal et al, 2010) and visual domains (Grice et al, 2001; Brown et al, 2005; Milne et al., 2009; Isler et al, 2010; Stroganova et al, 2012), suggesting a link between high-frequency oscillations and perceptual dysfunction. Lower frequency oscillatory activity has been described as affected in autism, such as impaired mu wave suppression during action observation (Oberman et al, 2005)
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