Altered modulation of gamma oscillation frequency by speed of visual motion in children with autism spectrum disorders.
BACKGROUND
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. Therefore, the experimental manipulations affecting gamma frequency may throw light on inhibitory networks dysfunction in ASD.


METHODS
Here, 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.


RESULTS
Although 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.


CONCLUSIONS
Our 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.
Autism Research Lab, MEG-Center, Moscow State University of Psychology and Education, Sretenka 29, Moscow, 107045 Russian Federation.
Tatiana A
TA
Stroganova
Autism Research Lab, MEG-Center, Moscow State University of Psychology and Education, Sretenka 29, Moscow, 107045 Russian Federation.
Anna V
AV
Butorina
Autism Research Lab, MEG-Center, Moscow State University of Psychology and Education, Sretenka 29, Moscow, 107045 Russian Federation.
Olga V
OV
Sysoeva
Autism Research Lab, MEG-Center, Moscow State University of Psychology and Education, Sretenka 29, Moscow, 107045 Russian Federation.
Andrey O
AO
Prokofyev
Autism Research Lab, MEG-Center, Moscow State University of Psychology and Education, Sretenka 29, Moscow, 107045 Russian Federation.
Anastasia Yu
AY
Nikolaeva
Autism Research Lab, MEG-Center, Moscow State University of Psychology and Education, Sretenka 29, Moscow, 107045 Russian Federation.
Marina M
MM
Tsetlin
Autism Research Lab, MEG-Center, Moscow State University of Psychology and Education, Sretenka 29, Moscow, 107045 Russian Federation.
Elena V
EV
Orekhova
ASD; Oblique line orientation threshold; Stimulus velocity; Visual gamma oscillation frequency