Department of Neurology, University of California, Irvine, CA 92697, United States.
Department of Psychological and Brain Sciences, University of California, Santa Barbara, CA, United States.
Neuropsychologia. 2014 Jan;53:197-202. doi: 10.1016/j.neuropsychologia.2013.11.021. Epub 2013 Dec 4.
Previous neuroimaging research has established that the left ventrolateral prefrontal cortex (VLPFC) is involved in long-term memory (LTM) encoding for individual items. Dorsolateral prefrontal cortex (DLPFC) is implicated less frequently, and one theory that has gained support to explain this discrepancy is that DLPFC is involved in forming item-item relational but not item LTM. Given that neuroimaging results are correlational, complimentary methods such as repetitive transcranial magnetic stimulation (TMS) have been used to test causal hypotheses generated from imaging data. Most TMS studies of LTM encoding have found that disruption of lateral PFC activity impairs subsequent memory. However these studies have lacked methods to precisely localize and directly compare TMS effects from frontal subregions implicated by the neuroimaging literature. Here, we target specific subregions of lateral PFC with TMS to test the prediction from the item/relational framework that temporary disruption of VLPFC during encoding will impair subsequent memory whereas TMS to DLPFC during item encoding will not. Frontal TMS was administered prior to a LTM encoding task in which participants were presented with a list of individual nouns and asked to judge whether each noun was concrete or abstract. After a 40 min delay period, item recognition memory was tested. Results indicate that VLPFC and DLPFC TMS have differential effects on subsequent item memory. VLPFC TMS reliably disrupted subsequent item memory whereas DLPFC TMS led to numerical enhancement in item memory, relative to TMS to a control region.
先前的神经影像学研究已经证实，左侧腹外侧前额叶皮层（VLPFC）参与了个体项目的长期记忆（LTM）编码。背外侧前额叶皮层（DLPFC）的参与则较少，有一种理论认为可以解释这种差异，即 DLPFC 参与形成项目间的关系，但不参与项目的 LTM。鉴于神经影像学结果是相关的，因此已经使用了重复经颅磁刺激（TMS）等补充方法来测试来自成像数据的因果假设。大多数关于 LTM 编码的 TMS 研究发现，破坏外侧 PFC 的活动会损害随后的记忆。然而，这些研究缺乏精确定位和直接比较神经影像学文献中涉及的额前区域 TMS 效应的方法。在这里，我们使用 TMS 靶向外侧 PFC 的特定亚区，以测试来自项目/关系框架的预测，即在编码期间暂时破坏 VLPFC 将损害随后的记忆，而在项目编码期间对 DLPFC 进行 TMS 则不会。在 LTM 编码任务之前，对前额 TMS 进行了管理，在此任务中，参与者会收到一组名词，并被要求判断每个名词是具体的还是抽象的。在 40 分钟的延迟期后，对项目识别记忆进行了测试。结果表明，VLPFC 和 DLPFC 的 TMS 对随后的项目记忆有不同的影响。VLPFC 的 TMS 确实破坏了随后的项目记忆，而 DLPFC 的 TMS 导致项目记忆的数值增强，与 TMS 到对照区域相比。
