Disrupted cortical neural inhibition has been hypothesized to be a primary contributor to the pathophysiology of autism spectrum disorder (ASD). This hypothesis predicts that ASD will be associated with an increase in neural responses. We tested this prediction by comparing fMRI response magnitudes to simultaneous visual, auditory, and motor stimulation in ASD and neurotypical (NT) individuals. No increases in the initial transient response in any brain region were observed in ASD, suggesting that there is no increase in overall cortical neural excitability. Most notably, there were widespread fMRI magnitude increases in the ASD response following stimulation offset, approximately 6–8 s after the termination of sensory and motor stimulation. In some regions, the higher fMRI offset response in ASD could be attributed to a lack of an “undershoot”—an often observed feature of fMRI responses believed to reflect inhibitory processing. Offset response magnitude was associated with reaction times (RT) in the NT group and may explain an overall reduced RT in the ASD group. Overall, our results suggest that increases in neural responsiveness are present in ASD but are confined to specific components of the neural response, are particularly strong following stimulation offset, and are linked to differences in RT.

中文翻译：

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晚期 fMRI 反应成分在自闭症谱系障碍中发生改变

中断的皮质神经抑制被假设是自闭症谱系障碍 (ASD) 病理生理学的主要因素。该假设预测 ASD 将与神经反应的增加有关。我们通过将 fMRI 反应幅度与 ASD 和神经典型 (NT) 个体的同时视觉、听觉和运动刺激进行比较来测试这一预测。在 ASD 中没有观察到任何大脑区域的初始瞬态反应增加，表明整体皮质神经兴奋性没有增加。最值得注意的是，在感觉和运动刺激终止后大约 6-8 秒，刺激抵消后 ASD 反应的 fMRI 幅度普遍增加。在一些地区，ASD 中较高的 fMRI 偏移反应可归因于缺乏“下冲”——fMRI 反应的一个经常观察到的特征，被认为反映了抑制性处理。偏移反应幅度与 NT 组的反应时间 (RT) 相关，可以解释 ASD 组的总体反应时间降低。总体而言，我们的结果表明 ASD 中存在神经反应性的增加，但仅限于神经反应的特定组成部分，在刺激抵消后特别强烈，并且与 RT 的差异有关。