Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA.
Hum Brain Mapp. 2013 Mar;34(3):566-74. doi: 10.1002/hbm.21459. Epub 2011 Nov 18.
Previous investigations of the default-mode network (DMN) in persons with attention-deficit/hyperactivity disorder (ADHD) have shown reduced functional connectivity between the anterior and posterior aspects. This finding was originally demonstrated in adults with ADHD, then in youth with ADHD, and has been tentatively linked to ultra low frequency oscillations within the DMN. The current study evaluates the specificity of DMN abnormalities to neuronal oscillations in the ultra low frequency range, and examines the regional specificity of these DMN aberrations in medicated and unmedicated adults with, and those without ADHD. An individually matched sample of adults with and without ADHD completed 6-minute sessions of resting-state magnetoencephalography (MEG). Participants with ADHD were known responders to stimulant medications and completed two sessions (predrug/postdrug). MEG data were coregistered to the participant's MRI, corrected for head motion, fitted to a regional-level source model, and subjected to spectral analyses to extract neuronal population activity in regions of the DMN. The unmedicated adults with ADHD exhibited broadband deficits in medial prefrontal cortices (MPFC), but not other DMN regions compared to adults without ADHD. Unmedicated patients also showed abnormal cross-frequency coupling in the gamma range between the MPFC and posterior cingulate areas, and disturbed balance within the DMN as activity in posterior regions was stronger than frontal regions at beta and lower frequencies, which dissipated at higher γ-frequencies. Administration of pharmacotherapy significantly increased prefrontal alpha activity (8-14 Hz) in adults with ADHD, and decreased the cross-frequency gamma coupling. These results indicate that neurophysiological aberrations in the DMN of patients with ADHD are not limited to ultra slow oscillations, and that they may be primarily attributable to abnormal broadband activity in the MPFC.
先前对注意缺陷多动障碍（ADHD）患者的默认模式网络（DMN）的研究表明，前后部分之间的功能连接减少。这一发现最初在 ADHD 成年患者中得到证实，然后在青少年 ADHD 患者中得到证实，并与 DMN 内的超低频率振荡初步相关。本研究评估了 DMN 异常与超低频率范围内神经元振荡的特异性，并检查了药物治疗和未治疗的 ADHD 成年患者以及无 ADHD 患者的这些 DMN 异常的区域特异性。一组年龄匹配的 ADHD 患者和非 ADHD 患者完成了 6 分钟的静息状态脑磁图（MEG）。已知 ADHD 患者对兴奋剂药物有反应，并完成了两次测试（用药前/用药后）。MEG 数据与参与者的 MRI 配准，对头部运动进行校正，拟合到区域水平的源模型，并进行频谱分析，以提取 DMN 区域中的神经元群体活动。与无 ADHD 的成年人相比，未经药物治疗的 ADHD 成年人的内侧前额叶皮层（MPFC）表现出广泛的宽带缺陷，但其他 DMN 区域没有。未经药物治疗的患者在 MPFC 和后扣带回区域之间的伽马范围内也表现出异常的跨频耦合，并且在 DMN 内的平衡受到干扰，因为后部区域的活动在β和较低频率下比前部区域强，在较高的γ频率下消失。药物治疗的实施显著增加了 ADHD 成年患者前额叶的α活动（8-14 Hz），并降低了跨频γ耦合。这些结果表明，ADHD 患者 DMN 的神经生理异常不仅限于超慢振荡，并且可能主要归因于 MPFC 中的异常宽带活动。
