Faculty of Psychology, Doshisha University, Kyotanabe, Japan.
Graduate School of Psychology, Doshisha University, Kyotanabe, Japan.
Eur J Neurosci. 2021 Jul;54(2):4595-4608. doi: 10.1111/ejn.15328. Epub 2021 Jun 21.
Interval timing-the perception of durations mainly in seconds or minutes-is a ubiquitous behavior in organisms. Animal studies have suggested that the hippocampus plays an essential role in duration memory; however, the memory processes involved are unclear. To clarify the role of the dorsal hippocampus in the acquisition of long-term duration memories, we adapted the "time-shift paradigm" to a peak-interval procedure. After a sufficient number of training with an initial target duration (20 s), the rats underwent "shift sessions" with a new target duration (40 s) under a muscimol (0.5 µg per side) infusion into the bilateral dorsal hippocampus. The memory of the new target duration was then tested in drug-free "probe sessions," including trials in which no lever presses were reinforced. In the probe sessions, the mean response rate distribution of the muscimol group was located leftward to the control group, but these two response rate distributions were superimposed on the standardized time axis, suggesting a scalar property. In the session-by-session analysis, the mean peak time (an index of timing accuracy) of the muscimol group was lower than that of the control group in the probe sessions, but not in the shift sessions. These findings suggest that the dorsal hippocampus is required for the formation of long-term duration memories within the range of interval timing.
间隔计时——主要是感知几秒钟或几分钟的时长——是生物体中普遍存在的行为。动物研究表明，海马体在时长记忆中起着至关重要的作用；然而，涉及的记忆过程尚不清楚。为了阐明背侧海马体在长期时长记忆获取中的作用，我们将“时间移位范式”改编为峰间隔程序。在经过足够数量的初始目标时长（20 秒）的训练后，大鼠在双侧背侧海马体中注入毒蕈碱（0.5µg 每侧）的情况下进行新目标时长（40 秒）的“移位会话”。然后，在无药物的“探针会话”中测试新目标时长的记忆，包括没有强化 lever press 的试验。在探针会话中，毒蕈碱组的平均反应率分布位于对照组的左侧，但这两个反应率分布叠加在标准化时间轴上，表明存在标度属性。在会话到会话的分析中，在探针会话中，毒蕈碱组的平均峰值时间（计时准确性的指标）低于对照组，但在移位会话中则不然。这些发现表明，背侧海马体是在间隔计时范围内形成长期时长记忆所必需的。
