Abstract
BackgroundRecent studies link autism spectrum disorders (ASD) with an altered balance between excitation and inhibition (E/I balance) in cortical networks. The brain oscillations in high gamma-band (50–120 Hz) are sensitive to the E/I balance and may appear useful biomarkers of certain ASD subtypes. The frequency of gamma oscillations is mediated by level of excitation of the fast-spiking inhibitory basket cells recruited by increasing strength of excitatory input. Therefore, the experimental manipulations affecting gamma frequency may throw light on inhibitory networks dysfunction in ASD.MethodsHere, we used magnetoencephalography (MEG) to investigate modulation of visual gamma oscillation frequency by speed of drifting annular gratings (1.2, 3.6, 6.0 °/s) in 21 boys with ASD and 26 typically developing boys aged 7–15 years. Multitaper method was used for analysis of spectra of gamma power change upon stimulus presentation and permutation test was applied for statistical comparisons. We also assessed in our participants visual orientation discrimination thresholds, which are thought to depend on excitability of inhibitory networks in the visual cortex.ResultsAlthough frequency of the oscillatory gamma response increased with increasing velocity of visual motion in both groups of participants, the velocity effect was reduced in a substantial proportion of children with ASD. The range of velocity-related gamma frequency modulation correlated inversely with the ability to discriminate oblique line orientation in the ASD group, while no such correlation has been observed in the group of typically developing participants.ConclusionsOur findings suggest that abnormal velocity-related gamma frequency modulation in ASD may constitute a potential biomarker for reduced excitability of fast-spiking inhibitory neurons in a subset of children with ASD.Electronic supplementary materialThe online version of this article (doi:10.1186/s11689-015-9121-x) contains supplementary material, which is available to authorized users.
Highlights
Recent studies link autism spectrum disorders (ASD) with an altered balance between excitation and inhibition (E/I balance) in cortical networks
The lack of the interaction between group and velocity suggests that the paradigm engaged attention of typically developing (TD) and ASD subjects in each velocity condition, and that any interactions between group and velocity found for the neurophysiological variables cannot be explained by differences in attention
Velocity-specific MEG gamma responses Inspection of grand average time–frequency plots for power changes shows a robust increase of high-frequency gamma oscillations (HGO) power within 50–120 Hz frequency range at each stimulus velocity, in both the TD and ASD groups
Summary
Recent studies link autism spectrum disorders (ASD) with an altered balance between excitation and inhibition (E/I balance) in cortical networks. The brain oscillations in high gamma-band (50–120 Hz) are sensitive to the E/I balance and may appear useful biomarkers of certain ASD subtypes. The frequency of gamma oscillations is mediated by level of excitation of the fast-spiking inhibitory basket cells recruited by increasing strength of excitatory input. The experimental manipulations affecting gamma frequency may throw light on inhibitory networks dysfunction in ASD. Stroganova et al Journal of Neurodevelopmental Disorders (2015) 7:21 common pathways for multiple molecular-genetic abnormalities in ASD [4, 5]. A plausible neurophysiological model explaining changes in brain functioning caused by abnormal activity of specific type of GABAergic interneurons—fast-spiking (FS) parvalbumin-expressing (PV+) cells—is an aberration in gamma oscillations (30–120 Hz) in cortical networks [8]. Pathological modifications of oscillatory gamma response properties may account for cognitive, perceptual, and motor dysfunctions that have been frequently observed in individuals with ASD since infancy [14]
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