Department of Psychological and Brain Sciences, Indiana University, Indiana.
Hippocampus. 2020 Feb;30(2):121-129. doi: 10.1002/hipo.23141. Epub 2019 Aug 27.
Spatial working memory is important for foraging and navigating the environment. However, its neural underpinnings remain poorly understood. The hippocampus, known for its spatial coding and involvement in spatial memory, is widely understood to be necessary for spatial working memory when retention intervals increase beyond seconds into minutes. Here, we describe new evidence that the dorsal hippocampus is not always necessary for spatial working memory for retention intervals of 8 min. Rats were trained to perform a delayed spatial win shift radial arm maze task with an 8-min delay between study and test phases. We then tested whether bilateral inactivation of the dorsal hippocampus between the study and test phases impaired behavioral performance at test. Inactivation was achieved through a bilateral infusion of lidocaine. Performance following lidocaine was compared to control trials, in which, sterile phosphate buffered saline (PBS) was infused. Test performance did not differ between the lidocaine and PBS conditions, remaining high in each. To explore the possibility that this insensitivity to inactivation was a result of overtraining, a second cohort of animals received substantially less training prior to the infusions. In this second cohort, lidocaine infusions did significantly impair task performance. These data indicate that successful performance of a spatial win-shift task on the 8-arm maze need not always be hippocampally dependent.
空间工作记忆对于觅食和导航环境很重要。然而，其神经基础仍知之甚少。海马体以其空间编码和参与空间记忆而闻名，当记忆间隔从几秒钟增加到几分钟时，人们普遍认为它对空间工作记忆是必要的。在这里，我们描述了新的证据，表明在 8 分钟的记忆间隔下，背侧海马体并不总是空间工作记忆所必需的。老鼠被训练在延迟的空间赢转变向放射臂迷宫任务中进行，在学习和测试阶段之间有 8 分钟的延迟。然后，我们测试了在学习和测试阶段之间双侧海马体失活是否会在测试时损害行为表现。失活是通过双侧注射利多卡因来实现的。在利多卡因和 PBS 条件下的表现没有差异，在每种情况下表现都很高。为了探索这种对失活不敏感的可能性是由于过度训练的结果，第二组动物在注射前接受了大量较少的训练。在第二组中，利多卡因注射确实显著损害了任务表现。这些数据表明，在 8 臂迷宫上成功执行空间赢转变任务不一定总是依赖于海马体。
