Globally elevated excitation-inhibition ratio in children with autism spectrum disorder and below-average intelligence

BACKGROUNDAn altered balance of neuronal excitation and inhibition (E-I balance) might be implicated in the co-occurrence of autism and intellectual disability, but this hypothesis has never been tested. E-I balance changes can be estimated from the spectral slope of the aperiodic 1/f neural activity. Herein, we used magnetoencephalography (MEG) to test whether the 1/f slope would differentiate ASD children with and without intellectual disability.METHODSMEG was recorded at rest with eyes open/closed in 49 boys with ASD aged 6-15 years with a broad range of IQs, and in 49 age-matched typically developing (TD) boys. The cortical source activity was estimated using the LCMV beamformer approach. We then extracted the 1/f slope by fitting a linear function in to the log-log-scale power spectra in the high-frequency range.RESULTSThe grand averaged 1/f slope was steeper in the eyes closed than in the eyes open condition, but had high rank-order stability between them. In line with the previous research, the slope flattened with age. Children with ASD and below-average (CONCLUSIONSThe atypically flattened spectral slope of aperiodic activity in children with ASD and below-average IQ suggests a shift of the global E-I balance toward hyper-excitation. The spectral slope can provide an accessible non-invasive biomarker of the E-I ratio for translational research and making objective judgments about treatment effectiveness.