意识下与意识上恐惧习得的神经振荡机制的对比
文献类型：学位论文
| 作者 | 陈思 |
| 答辩日期 | 2023-06 |
| 文献子类 | 博士 |
| 授予单位 | 中国科学院大学 |
| 授予地点 | 中国科学院心理研究所 |
| 其他责任者 | 王亮 |
| 关键词 | 恐惧习得 意识 杏仁核 内侧前额叶 颅内脑电 |
| 学位名称 | 理学博士 |
| 学位专业 | 认知神经科学 |
| 其他题名 | Comparison of neural oscillatory mechanisms between unconscious and conscious fear acquisition |
| 中文摘要 | The emotion of fear has important implications for human adaptation and evolution. However, excessive fear can lead to a series of mental illnesses. How to treat fear-related diseases is an urgent problem to be solved clinically. Evidence from a large number of studies shows that compared with neutral, non-emotional information, the brain is less dependent on the state of consciousness when processing emotional information, and can even proceed in a unconscious state. Not only that, the researchers found that fear conditioning can also be successfully established in the subconscious state, and its development process is significantly different from that of conscious fear conditioning. However, the neural mechanism of unconscious fear conditioning is still unclear. In this study, three studies are used to explore the process of unconscious fear acquisition caused by sensory changes and its neural mechanism, and compare it with the process of conscious fear acquisition. The three studies are described as follows: In Study 1，we designed an unconscious fear conditioning task. The experimental stimulus was two colored gratings with different orientations, presented as low spatial frequency(LSF)and high spatial frequency(HSF)in Study la and Study 1 b, respectively. The orientation of gratings is made invisible using the Critical Flicker Frequency (CFF) paradigm. One of the colored gratings was bound to fear conditioning with negative electrical stimulation (CS+), the other was always presented alone (CS一). Pupil data were recorded when the subjects completed the task. In this study, we recruited 46 healthy subjects (34 were finally included in the analysis). It was found that even when a neutral stimulus that has nothing to do with fear was used as a conditioned stimulus, a significant difference in the conditioned responses of CS+ and CS一could be observed in unconscious fear conditioning, and this difference occurred specifically in the LSF and not in the case of HSF. This provides strong evidence that neutral stimuli can be effectively associated with the US in the unconscious state, while the results support the dependence of unconscious fear processing on LSF. In Study 2, we used the within-group design method, and a total of 11 epilepsy patients were required to complete the unconscious and conscious fear conditioning successively. The intracranial electroencephalography(iEEG)data and pupil data were simultaneously recorded during the task. Our results found that, at different levels of consciousness, the different responses of the human amygdala to CS+ and CS一all occurred within a very fast latency period (about 60 ms), earlier than the processing of emotional information and the separation of visual features by inferior temporal cortex (ITC). Further analysis found that activity in the amygdala precedes the ITC early in the presentation of subthreshold stimuli, and shifts to ITC earlier than the amygdala in the later stages. These results are consistent with the idea that rapid subthreshold detection of threatening stimuli by the amygdala is modulated by information from subcortical pathways that bypass the visual cortex, thus providing direct empirical support for the 'low-road' idea. At the same time, we also found that there are significant differences in the patterns of event-related potential (ERP) at different levels of consciousness, suggesting that the two may involve different neural mechanisms. In Study 3, our experimental design was consistent with Study 2 and a total of 10 epilepsy patients' data were included in the analysis二It was found that under different levels of consciousness, both the amygdala and the ventral medial prefrontal cortex (vmPFC) showed significant changes in theta oscillations, and the functional connectivity of the two brain regions was enhanced. This result provides the first direct electrophysiological evidence for the involvement of the amygdala and vmPFC in unconscious fear conditioning. In addition, we found that during unconscious fear learning, the amygdala exhibited enhanced low theta power and decreased high theta power; whereas the vmPFC exhibited enhanced high and low theta oscillations during unconscious and conscious tasks, respectively. This suggests that the low theta and high theta oscillation of the amygdala may play different roles in unconscious fear conditioning, while different frequency bands in theta oscillations of the vmPFC are involved in unconscious and conscious fear processing, respectively. Furthermore, our results found that electrodes located in the ventral posterior vmPFC were more active when CS+ was presented, while electrodes located in the dorsal anterior vmPFC were more active when CS-. This provides key evidence support that different subregion of the vmPFC play different roles in fear learning. Analysis of directionality in two brain regions found that during unconscious fear learning, this synchronicity was initially driven by the amygdala and later gradually shifted to be driven by the vmPFC. This result suggests that during fear acquisition, the amygdala relies on projections to the vmPFC to shape activity in the vmPFC, resulting in enhanced vmPFC output. At the same time, we found that in the conscious fear conditioning, the information transmission between the amygdala and vmPFC was driven by the vmPFC in the early stage of stimulus presentation, but gradually changed to be driven by the amygdala in the later stage of stimulus presentation. This may be due to the heavy use of attentional resources required for conscious tasks. Finally, we found that during conscious fear learning, low theta power in the amygdala and mPFC showed a tendency to increase significantly with learning progress. In the unconscious task, there is no significant change in theta power. The above findings suggest that unconscious fear conditioning based on neutral stimuli can be established relying on LSF, and during this process, the synchronized activity of the amygdala-mPFC circuit in the theta band promotes fear learning. Although the amygdala-mPFC circuit plays an important role in fear learning at different levels of consciousness, the mechanism of these two is different, which is reflected in many variables involving discrete patterns of oscillatory activity, different learning processes and opposite direction of functional connectivity in amygdala-mPFC circuit. These works will help us better understand the formation of fear memories, and provide some reference for future intervention and treatment of fear diseases. The above findings suggest that unconscious fear conditioning based on neutral stimuli can be established relying on LSF. In fear learning at different levels of consciousness, the different responses of the human amygdala to CS+ and CS一all occurred at very fast latencies, earlier than processing of emotional information and separation of simple visual features in the ITC. The synchronized activity between the amygdala and mPFC in the theta band promotes the establishment of fear conditioning, but there are different neural mechanisms at different levels of consciousness, which are reflected in the oscillation patterns within and between brain regions, the process of learning and the directionality of information transmission across brain regions. These works will help us better understand the formation of fear memory, and provide some reference for the intervention and treatment of phobia. |
| 英文摘要 | 恐惧情绪对人类的适应和进化具有重要意义。然而过度的恐惧会导致一系列的精神疾病，如何治疗恐惧相关疾病是现在临床上巫待解决的问题。大量研究的证据表明，相比于中性的不带情绪色彩的信息，大脑在加工情绪信息时对意识状态的依赖性更低，甚至可以在意识下的状态下进行加工。不仅如此，研究人员发现恐惧条件化可以在意识下的状态成功地建立，且其发展进程与意识上恐惧条件化存在着显著不同。但关于意识下恐惧条件化的神经机制目前还不清楚。本文通过三个研究探讨感觉改变引发的意识下恐惧习得的过程及其神经机制，并将其与意识上恐惧习得的过程进行对比，三项研究分述如下: 在研究一中我们设计了一个意识下的恐惧条件反射任务，实验刺激是两个不同朝向的彩色光栅，在研究la和研究1b中分别以低空间频率(low spatial frequency LSF)和高空间频率(high spatial frequency HSF)呈现。使用闪光融合范式(critical flicker-fusion frequency CFF)使得光栅朝向不可见。将其中一个彩色光栅与负性电刺激进行恐惧条件化绑定(CS+)，另一个则总是单独呈现 ( CS-)。在被试完成任务时记录其眼动数据。在本研究中我们共招募了46名健康被试(最终有34名纳入分析)。结果发现，即使是将与恐惧无关的中性刺激作为条件刺激，也可以在意识下的恐惧条件反射中观察到CS+与CS一的瞳孔反应出现显著差异，且这种差异特异性地发生在LSF而不是HSF的情况下。该结果为中性刺激可以在无意识状态下有效地与US相关联提供了强有力的证据，同时支持了意识下的恐惧处理依赖于LSF。 在研究二中我们使用组内设计的方式，共11名癫痈患者先后完成意识下和意识上的恐惧条件反射任务，在任务期间同步记录其颅内脑电(intracranial electroencephalography, iEEG)数据和眼动数据。我们发现，在不同的意识水平下，人类杏仁核对CS+和CS一的不同反应均在非常快的潜伏期内发生(约60ms)，早于颗下回(inferior temporal cortex, ITC)对情绪信息的加工和对视觉特征的分离。对两个脑区的信号进行互相关分析发现，在意识下CS+呈现后，两个大脑区域的信息流向逐渐从杏仁核引导ITC转变为ITC引导杏仁核。这些结果与杏仁核对意识下的威肋、刺激地快速检测是由绕过视觉皮层的皮层下通路的信息调制的观点一致，从而为“low-road”观点提供了实证支持。同时我们也发现不同意识水平下的事件相关电位(event-related potential, ERP)的幅值形态有显著差异，提示我们两者可能涉及不同的神经机制。 在研究三中，我们的实验设计与研究二一致，共有10名癫痫者的实验数据被纳入分析。结果发现，不同的意识水平下，杏仁核和腹内侧（ ventral medial prefrontal cortex, vmPFC)均表现出theta振荡的显著变化，且两个脑区间的活动一致性增强。该结果首次为杏仁核和vmPFC参与意识下恐惧条件反射提供了直接的电生理证据。除此之外，我们发现在意识下的恐惧学习中，杏仁核中的low theta功率增加，high theta功率降低;而vmPFC在意识下和意识上的任务中分别表现为high theta和low theta振荡增强。这提示我们，杏仁核的low theta和high theta振荡可能在意识下恐惧条件反射中存在着特异性的分工，而vmPFC的不同频段的theta振荡则特异性地参与到意识下和意识上恐惧加工中。此外，我们的结果发现位于vmPFC腹侧后部的电极在呈现CS+时具有更强的活性，而位于vmPFC背侧前部的电极则在呈现CS一时更活跃，从而为vmPFC不同子区在恐惧学习中发挥不同作用提供了关键的证据支持。对两个脑区的方向性分析发现，在意识下的恐惧学习中，这种同步性最初由杏仁核驱动，后期逐渐转变为由vmPFC驱动。该结果表明，在恐惧习得期间，杏仁核依赖于对于vmPFC的投射来塑造vmPFC中的活动，从而导致vmPFC输出增强。同时我们发现，在意识上的恐惧条件反射中，杏仁核与vmPFC之间的信息传递在刺激呈现的初期由vmPFC驱动，但在刺激呈现后期逐渐转变为由杏仁核驱动，这可能是由于在意识上的任务重需要调用更多的注意力资源所致。最后，我们发现在意识上的恐惧学习中，杏仁核与mPFC中的low theta功率表现出随着学习进程显著增加的趋势。而在意识下的情况，theta功率无明显变化。 以上研究结果表明，基于中性刺激的意识下恐惧条件化可以依赖LSF建立。在不同意识水平下的恐惧学习中，人类杏仁核对CS+和CS一的不同反应均在非常快的潜伏期内发生，早于ITC对情绪信息的加工和对视觉特征的分离。杏仁核-mPFC环路在theta频段的协同活动促进了恐惧条件化的建立，但在不同意识水平下存在不同的神经机制，体现在脑区内和脑区间的振荡模式、学习的进程和跨脑区信息传递的方向性等方面。这些工作将有助于我们更好地理解恐惧记忆的形成，为恐惧症的干预和治疗提供一定的参考。 |
| 语种 | 中文 |
| 源URL | [http://ir.psych.ac.cn/handle/311026/46150]  |
| 专题 | 心理研究所_健康与遗传心理学研究室 |
| 推荐引用方式 GB/T 7714 | 陈思. 意识下与意识上恐惧习得的神经振荡机制的对比[D]. 中国科学院心理研究所. 中国科学院大学. 2023. |
入库方式： OAI收割
来源：心理研究所
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