Department of Brain & Cognitive Sciences, Seoul National University, Seoul, 03080, Republic of Korea; Department of Neurosurgery, Seoul National University Hospital, Seoul, 03080, Republic of Korea.
Department of Bio & Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea.
Brain Stimul. 2020 May-Jun;13(3):603-613. doi: 10.1016/j.brs.2020.01.013. Epub 2020 Jan 25.
Despite its potential to revolutionize the treatment of memory dysfunction, the efficacy of direct electrical hippocampal stimulation for memory performance has not yet been well characterized. One of the main challenges to cross-study comparison in this area of research is the diversity of the cognitive tasks used to measure memory performance.
We hypothesized that the tasks that differentially engage the hippocampus may be differentially influenced by hippocampal stimulation and the behavioral effects would be related to the underlying hippocampal activity.
To investigate this issue, we recorded intracranial EEG from and directly applied stimulation to the hippocampus of 10 epilepsy patients while they performed two different verbal memory tasks - a word pair associative memory task and a single item memory task.
Hippocampal stimulation modulated memory performance in a task-dependent manner, improving associative memory performance, while impairing item memory performance. In addition, subjects with poorer baseline cognitive function improved much more with stimulation. iEEG recordings from the hippocampus during non-stimulation encoding blocks revealed that the associative memory task elicited stronger theta oscillations than did item memory and that stronger theta power was related to memory performance.
We show here for the first time that stimulation-induced associative memory enhancement was linked to increased theta power during retrieval. These results suggest that hippocampal stimulation enhances associative memory but not item memory because it engages more hippocampal theta activity and that, in general, increasing hippocampal theta may provide a neural mechanism for successful memory enhancement.
尽管直接电刺激海马体有潜力彻底改变记忆功能障碍的治疗方法，但它对记忆表现的疗效尚未得到充分描述。在该研究领域进行跨研究比较的主要挑战之一是用于测量记忆表现的认知任务的多样性。
我们假设，那些能够差异化地激活海马体的任务可能会受到海马体刺激的差异化影响，并且行为效应与潜在的海马体活动有关。
为了研究这个问题，我们在 10 名癫痫患者进行两项不同的言语记忆任务（单词对联想记忆任务和单项记忆任务）时，记录了他们的颅内 EEG 并直接对海马体施加刺激。
海马体刺激以任务依赖的方式调节记忆表现，改善联想记忆表现，同时损害单项记忆表现。此外，基线认知功能较差的受试者在接受刺激后改善得更多。在非刺激编码期间从海马体记录的 iEEG 显示，联想记忆任务比单项记忆任务引发更强的 theta 振荡，并且更强的 theta 功率与记忆表现相关。
我们在这里首次展示，刺激引起的联想记忆增强与提取过程中增加的 theta 功率有关。这些结果表明，海马体刺激增强联想记忆而不是单项记忆，因为它会引发更多的海马体 theta 活动，并且通常来说，增加海马体 theta 可能为成功的记忆增强提供神经机制。
