Lenz Daniel, Krauel Kerstin, Schadow Jeanette, Baving Lioba, Duzel Emrah, Herrmann Christoph S
Otto-von-Guericke-University Magdeburg, Department of Biological Psychology, P.O. Box 4120, 39016 Magdeburg, Germany.
Brain Res. 2008 Oct 15;1235:117-32. doi: 10.1016/j.brainres.2008.06.023. Epub 2008 Jun 19.
Previous electrophysiological as well as imaging research has contributed to the understanding of impairments in attention, executive functions, and memory in patients with attention-deficit/hyperactivity disorder (ADHD). However, there is a lack of studies investigating ADHD related differences in the gamma range of human electroencephalogram (EEG), although gamma activity is strongly associated with cognitive processes impaired in ADHD patients and is also modulated by dopamine polymorphisms linked with ADHD. To close this gap, the present study compared gamma activity in ADHD children with that of healthy controls and correlated it with memory performance. EEG was recorded from 13 ADHD patients as well as 13 healthy control subjects during the encoding phase of a visual memory paradigm. In a subsequent recognition test, participants had to judge pictures as being old or new. Analysis of evoked gamma-band responses (GBRs) during stimulus encoding revealed a strong task-related enhancement for ADHD patients in parieto-occipital areas. Interestingly, this augmentation was not associated with recognition performance, whereas healthy subjects exhibited a strong positive correlation between evoked gamma activity during stimulus encoding and subsequent recognition performance. We interpret this finding as evidence of enhanced excitation levels and unspecific activation of processing resources in ADHD patients. Furthermore, enhanced GBRs in ADHD could also indicate a decrease of neuronal signal-to-noise ratio, partially caused by the genetic variations within the dopaminergic pathway of ADHD patients. The involved genetic polymorphisms have been shown to modulate evoked GBRs, which therefore could be a possible marker of impaired neurotransmission in ADHD.
先前的电生理以及影像学研究有助于理解注意力缺陷多动障碍（ADHD）患者在注意力、执行功能和记忆方面的损伤。然而，尽管伽马活动与ADHD患者受损的认知过程密切相关，且也受到与ADHD相关的多巴胺多态性的调节，但缺乏对人类脑电图（EEG）伽马频段中与ADHD相关差异的研究。为了填补这一空白，本研究比较了ADHD儿童与健康对照者的伽马活动，并将其与记忆表现进行关联。在视觉记忆范式的编码阶段，对13名ADHD患者以及13名健康对照者进行了EEG记录。在随后的识别测试中，参与者必须判断图片是旧的还是新的。对刺激编码期间诱发的伽马波段反应（GBR）的分析显示，ADHD患者在顶枕区域有强烈的任务相关增强。有趣的是，这种增强与识别表现无关，而健康受试者在刺激编码期间诱发的伽马活动与随后的识别表现之间呈现出强烈的正相关。我们将这一发现解释为ADHD患者兴奋水平增强和处理资源非特异性激活的证据。此外，ADHD患者中增强的GBR也可能表明神经元信噪比降低，部分原因是ADHD患者多巴胺能通路内的基因变异。所涉及的基因多态性已被证明可调节诱发的GBR，因此这可能是ADHD神经传递受损的一个可能标志物。
