Objective: The abnormality of intrinsic brain activity in autism spectrum disorders (ASDs) is still inconclusive. Contradictory results have been found pointing towards hyper-activity or hypo-activity in various brain regions. The present research aims to investigate the spatial and spectral signatures of aberrant brain activity in an unprecedented frequency range of 1-2884 Hz at source levels in ASD using newly developed methods.
Materials and methods: Seven ASD subjects and age- and gender-matched controls were studied using a high-sampling rate magnetoencephalography (MEG) system. Brain activity in delta (1-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), beta (12-30 Hz), low gamma (30-55 Hz), high gamma (65-90 Hz), ripples (90-200 Hz), high-frequency oscillations (HFOs, 200-1000 Hz), and very high-frequency oscillations (VHFOs, 1000-2884 Hz) was volumetrically localized and measured using wavelet and beamforming.
Results: In comparison to controls, ASD subjects had significantly higher odds of alpha activity (8-12 Hz) in the sensorimotor cortex (mu rhythm), and generally high-frequency activity (90-2884 Hz) in the frontal cortex. The source power of HFOs (200-1000 Hz) in the frontal cortex in ASD was significantly elevated as compared with controls.
Conclusion: The results suggest that ASD has significantly altered intrinsic brain activity in both low- and high-frequency ranges. Increased intrinsic high-frequency activity in the frontal cortex may play a key role in ASD.
Keywords: Autism spectrum disorders (ASDs); High-frequency oscillations; Intrinsic brain activity; Magnetic source imaging; Magnetoencephalography (MEG); Mu rhythm.
Copyright © 2015 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.