改变的神经元兴奋-抑制(E-I)平衡与ASD密切相关。然而,目前尚不清楚ASD患者E-I比值变化的方向和程度是否与通常与这种发育障碍相关的智力障碍相关.非周期性1/f活性的光谱斜率反映了大神经元种群规模的E-I平衡,并且可能揭示其在有或没有智力障碍的ASD个体中的推定交替。
这里,我们使用脑磁图(MEG)来测试1/f斜率是否可以区分智商平均和低于平均水平(<85)的ASD儿童。在49名年龄在6-15岁之间,智商在54至128岁的ASD男孩以及49名年龄匹配的典型发育(TD)男孩中,睁眼/闭眼时记录了MEG。使用波束形成器方法和个体大脑模型估计皮质源活动。然后,我们通过将线性函数拟合到高频范围内的对数-对数尺度功率谱来提取1/f斜率。
在所有皮质源上平均的全局1/f斜率显示了两种条件之间的高秩稳定性。与以前的研究一致,闭眼时比睁眼时更陡,并随着年龄的增长而变平。不管条件如何,与智商平均或高于平均水平的TD或ASD儿童相比,智商低于平均水平的ASD儿童的斜率更平坦。这些组差异不能用信噪比或周期性(α和β)活动的差异来解释。
需要进一步的研究来确定所观察到的E-I比率的变化是否是其他诊断组智商低于平均水平的儿童的特征。
患有ASD且智商低于平均水平的儿童的非周期性活动的非典型平坦的光谱斜率表明,全球E-I平衡向过度兴奋转变。光谱斜率可以提供E-I比率的可获得的非侵入性生物标志物,用于对患有ASD和合并症智力残疾的人的治疗有效性做出客观判断。
Altered neuronal excitation-inhibition (E-I) balance is strongly implicated in ASD. However, it is not known whether the direction and degree of changes in the E-I ratio in individuals with ASD correlates with intellectual disability often associated with this developmental disorder. The spectral slope of the aperiodic 1/f activity reflects the E-I balance at the scale of large neuronal populations and may uncover its putative alternations in individuals with ASD with and without intellectual disability.
Herein, we used magnetoencephalography (MEG) to test whether the 1/f slope would differentiate ASD children with average and below-average (< 85) IQ. MEG was recorded at rest with eyes open/closed in 49 boys with ASD aged 6-15 years with IQ ranging from 54 to 128, and in 49 age-matched typically developing (TD) boys. The cortical source activity was estimated using the beamformer approach and individual brain models. We then extracted the 1/f slope by fitting a linear function to the log-log-scale power spectra in the high-frequency range.
The global 1/f slope averaged over all cortical sources demonstrated high rank-order stability between the two conditions. Consistent with previous research, it was steeper in the eyes-closed than in the eyes-open condition and flattened with age. Regardless of condition, children with ASD and below-average IQ had flatter slopes than either TD or ASD children with average or above-average IQ. These group differences could not be explained by differences in signal-to-noise ratio or periodic (alpha and beta) activity.
Further research is needed to find out whether the observed changes in E-I ratios are characteristic of children with below-average IQ of other diagnostic groups.
The 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 noninvasive biomarker of the E-I ratio for making objective judgments about treatment effectiveness in people with ASD and comorbid intellectual disability.