Segobin Shailendra, Renault Cyrielle, Viader Fausto, Eustache Francis, Pitel Anne Lise, Quinette Peggy
Normandie University, UNICAEN, PSL Research University, EPHE, INSERM, U1077, CHU de Caen, Cyceron, Neuropsychologie et Imagerie de la Mémoire Humaine, 14032, Caen, Normandie, France.
Normandie University, UNICAEN, INSERM, U1237, PhIND 'Physiopathology and Imaging of Neurological Disorders', Cyceron, 14032, Caen, Normandie, France.
Brain Commun. 2023 Mar 21;5(2):fcad082. doi: 10.1093/braincomms/fcad082. eCollection 2023.
Transient global amnesia is characterized by the sudden apparition of severe episodic amnesia, mainly anterograde, associated with emotional changes. Even though the symptoms are stereotyped, cerebral mechanism underlying transient global amnesia remains unexplained and previous studies using positron emission tomography do not show any clear results or consensus on cerebral regions impacted during transient global amnesia. This study included a group of 10 transient global amnesic patients who underwent F-fluorodeoxyglucose positron emission tomography during the acute or recovery phase of the episode and 10 paired healthy controls. Episodic memory was evaluated with the encoding-storage-retrieval paradigm and a story recall test of the Wechsler's memory scale and anxiety was assessed with the Spielberger scale. We used statistical parametric mapping to identify modifications of whole-brain metabolism. Regarding hypometabolism, there was no brain region systematically affected in all transient global amnesic patients and the comparison between amnesic patients and controls did not show any significant differences. To better understand the specific implication of the limbic circuit in the pathophysiology of transient global amnesia, we then conducted a correlational analysis that included regions of this network. Our findings showed that in healthy controls, regions of the limbic circuit seem to operate in a synchronized way with all regions being highly correlated to each other. On the opposite, in transient global amnesic patients, we observed a clear disruption of this normal correlational patterns between regions with the medial temporal lobe (the hippocampus, parahippocampal gyrus and amygdala) included in one cluster and the orbitofrontal cortex, anterior and posterior cingulate gyrus and thalamus gathered in the other one. Given the individual variability in the time course of transient global amnesia, the direct comparison between a group of patients and controls does not seem to favour the identification of subtle and transient alterations in regional metabolism. The involvement of an extended network, such as the limbic circuit, seems more likely to explain the symptoms of patients. Indeed, the synchronization of regions within the limbic circuit seems to be altered during transient global amnesia, which could explain the amnesia and anxiety observed in transient global amnesic patients. The present study thus deepens our understanding of the mechanisms underlying not only amnesia but also the emotional component of transient global amnesia by considering it as a disruption in the normal correlational patterns within the limbic circuit.
短暂性全面性遗忘症的特征是突然出现严重的发作性遗忘，主要是顺行性遗忘，并伴有情绪变化。尽管症状具有刻板性，但短暂性全面性遗忘症的脑机制仍未得到解释，先前使用正电子发射断层扫描的研究并未显示出关于短暂性全面性遗忘症发作期间受影响脑区的任何明确结果或共识。本研究纳入了一组10名短暂性全面性遗忘症患者，他们在发作的急性期或恢复期接受了F-氟脱氧葡萄糖正电子发射断层扫描，以及10名配对的健康对照者。采用编码-存储-检索范式和韦氏记忆量表的故事回忆测试评估情景记忆，并用斯皮尔伯格量表评估焦虑。我们使用统计参数映射来识别全脑代谢的变化。关于代谢减低，在所有短暂性全面性遗忘症患者中没有系统受影响的脑区，遗忘症患者与对照者之间的比较也未显示出任何显著差异。为了更好地理解边缘回路在短暂性全面性遗忘症病理生理学中的具体作用，我们随后进行了一项相关性分析，该分析纳入了该网络的区域。我们的研究结果表明，在健康对照者中，边缘回路的区域似乎以同步方式运作，所有区域彼此高度相关。相反，在短暂性全面性遗忘症患者中，我们观察到区域之间这种正常相关模式的明显破坏，内侧颞叶（海马体、海马旁回和杏仁核）包含在一个簇中，眶额皮质、前扣带回和后扣带回以及丘脑聚集在另一个簇中。鉴于短暂性全面性遗忘症病程的个体差异，一组患者与对照者之间的直接比较似乎不利于识别区域代谢中细微和短暂的变化。一个扩展网络，如边缘回路的参与，似乎更有可能解释患者的症状。事实上，在短暂性全面性遗忘症发作期间，边缘回路内区域的同步性似乎发生了改变，这可以解释短暂性全面性遗忘症患者中观察到的遗忘和焦虑。因此，本研究通过将短暂性全面性遗忘症视为边缘回路内正常相关模式的破坏，不仅加深了我们对遗忘症机制的理解，也加深了对其情绪成分的理解。
