How to detect amygdala activity with magnetoencephalography using source imaging.
How to detect amygdala activity with magnetoencephalography using source imaging.
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DOI：
10.3791/50212
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发表时间：
2013-06-03
期刊：
影响因子：
--
通讯作者：
Helmstetter FJ
中科院分区：
文献类型：
--
作者：
Balderston NL;Schultz DH;Baillet S;Helmstetter FJ
在微量恐惧调节中，条件刺激 (CS) 预测无条件刺激 (UCS) 的发生，无条件刺激 (UCS) 在短暂的无刺激期（微量间隔）1 后出现。由于 CS 和 UCS 不会在时间上同时出现，因此受试者必须在跟踪间隔期间保持该 CS 的表示。对于人类来说，这种类型的学习需要意识到刺激的偶然性，以便弥合轨迹间隔 2-4。然而，当将面部用作 CS 时，即使没有明确的意识*，受试者也可以隐性地学会害怕面部。这表明可能存在额外的神经机制能够在短暂的跟踪间隔期间维持某些类型的“生物学相关”刺激。鉴于杏仁核参与跟踪调节，并且对面部敏感，因此该结构可能可以在短暂的跟踪间隔内维持面部 CS 的表示。尽管这两种刺激在时间上是分开的，但理解大脑如何将未被察觉的面孔与令人厌恶的结果联系起来是具有挑战性的。此外，由于两个具体挑战，对这种现象的调查变得困难。首先，很难操纵受试者对视觉刺激的意识。操纵视觉意识的一种常见方法是使用后向掩蔽。在后向掩蔽中，目标刺激会被短暂呈现（< 30 毫秒），然后立即呈现重叠掩蔽刺激5。面具的出现使目标变得不可见6-8。其次，掩蔽需要非常快速和精确的计时，这使得使用许多常见方法研究掩蔽刺激引起的神经反应变得困难。血氧水平依赖性 (BOLD) 响应的解析时间尺度对于此类方法而言太慢，并且脑电图 (EEG) 和脑磁图 (MEG) 等实时记录技术难以从深部源恢复信号。然而，用于定位 MEG 信号神经源的方法最近取得了进展9-11。通过收集受试者大脑的高分辨率 MRI 图像，可以创建基于个体神经解剖结构的源模型。使用该模型对 MEG 信号源进行“成像”，可以从深层皮层下结构（如杏仁核和海马体*）恢复信号。
In trace fear conditioning a conditional stimulus (CS) predicts the occurrence of the unconditional stimulus (UCS), which is presented after a brief stimulus free period (trace interval)1. Because the CS and UCS do not co-occur temporally, the subject must maintain a representation of that CS during the trace interval. In humans, this type of learning requires awareness of the stimulus contingencies in order to bridge the trace interval2-4. However when a face is used as a CS, subjects can implicitly learn to fear the face even in the absence of explicit awareness*. This suggests that there may be additional neural mechanisms capable of maintaining certain types of "biologically-relevant" stimuli during a brief trace interval. Given that the amygdala is involved in trace conditioning, and is sensitive to faces, it is possible that this structure can maintain a representation of a face CS during a brief trace interval. It is challenging to understand how the brain can associate an unperceived face with an aversive outcome, even though the two stimuli are separated in time. Furthermore investigations of this phenomenon are made difficult by two specific challenges. First, it is difficult to manipulate the subject's awareness of the visual stimuli. One common way to manipulate visual awareness is to use backward masking. In backward masking, a target stimulus is briefly presented (< 30 msec) and immediately followed by a presentation of an overlapping masking stimulus5. The presentation of the mask renders the target invisible6-8. Second, masking requires very rapid and precise timing making it difficult to investigate neural responses evoked by masked stimuli using many common approaches. Blood-oxygenation level dependent (BOLD) responses resolve at a timescale too slow for this type of methodology, and real time recording techniques like electroencephalography (EEG) and magnetoencephalography (MEG) have difficulties recovering signal from deep sources. However, there have been recent advances in the methods used to localize the neural sources of the MEG signal9-11. By collecting high-resolution MRI images of the subject's brain, it is possible to create a source model based on individual neural anatomy. Using this model to "image" the sources of the MEG signal, it is possible to recover signal from deep subcortical structures, like the amygdala and the hippocampus*.
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