Department of Neurology, Campus Benjamin Franklin, Charité-University Medicine, Berlin, Germany.
PLoS One. 2012;7(3):e33691. doi: 10.1371/journal.pone.0033691. Epub 2012 Mar 22.
Subjects with Attention-Deficit Hyperactivity Disorder (ADHD) are overdistractible by stimuli out of the intended focus of attention. This control deficit could be due to primarily reduced attentional capacities or, e. g., to overshooting orienting to unexpected events. Here, we aimed at identifying disease-related abnormalities of novelty processing and, therefore, studied event-related potentials (ERP) to respective stimuli in adult ADHD patients compared to healthy subjects.
Fifteen unmedicated subjects with ADHD and fifteen matched controls engaged in a visual oddball task (OT) under simultaneous EEG recordings. A target stimulus, upon which a motor response was required, and non-target stimuli, which did not demand a specific reaction, were presented in random order. Target and most non-target stimuli were presented repeatedly, but some non-target stimuli occurred only once ('novels'). These unique stimuli were either 'relative novels' with which a meaning could be associated, or 'complete novels', if no association was available.
In frontal recordings, a positive component with a peak latency of some 400 ms became maximal after novels. In healthy subjects, this novelty-P3 (or 'orienting response') was of higher magnitude after complete than after relative novels, in contrast to the patients with an undifferentially high frontal responsivity. Instead, ADHD patients tended to smaller centro-parietal P3 responses after target signals and, on a behavioural level, responded slower than controls.
The results demonstrate abnormal novelty processing in adult subjects with ADHD. In controls, the ERP pattern indicates that allocation of meaning modulates the processing of new stimuli. However, in ADHD such a modulation was not prevalent. Instead, also familiar, only context-wise new stimuli were treated as complete novels. We propose that disturbed semantic processing of new stimuli resembles a mechanism for excessive orienting to commonly negligible stimuli in ADHD.
患有注意力缺陷多动障碍（ADHD）的受试者容易被注意力之外的刺激分散注意力。这种控制缺陷可能是由于注意力能力降低，也可能是由于对意外事件的过度定向。在这里，我们旨在确定与疾病相关的新颖性处理异常，因此，与健康受试者相比，我们研究了成年 ADHD 患者对相应刺激的事件相关电位（ERP）。
15 名未经药物治疗的 ADHD 患者和 15 名匹配的对照者在同时进行脑电图记录的情况下参与了视觉Oddball 任务（OT）。目标刺激，需要进行运动反应，非目标刺激，不需要特定反应，随机呈现。目标和大多数非目标刺激重复出现，但有些非目标刺激仅出现一次（“新颖刺激”）。这些独特的刺激要么是可以与之建立联系的“相对新颖刺激”，要么是如果没有关联，则是“完全新颖刺激”。
在前额记录中，一个正成分的峰值潜伏期约为 400 毫秒，在新颖刺激后达到最大值。在健康受试者中，与相对新颖刺激相比，完整新颖刺激后的 novelty-P3（或“定向反应”）幅度更高，而与患者的前额反应性无差异相反。相反，ADHD 患者在目标信号后倾向于产生较小的中央顶叶 P3 反应，并且在行为水平上比对照组反应较慢。
这些结果表明，成年 ADHD 患者的新颖性处理异常。在对照者中，ERP 模式表明，分配意义会调节新刺激的处理。然而，在 ADHD 中，这种调节并不普遍。相反，即使是熟悉的、仅在上下文上新颖的刺激，也被视为完整的新颖刺激。我们提出，新刺激的语义处理障碍类似于 ADHD 中对通常可忽略不计的刺激进行过度定向的机制。
