Durkin T P
Laboratoire de Neurosciences Comportementales et Cognitives, Université de Bordeaux 1, Talence, France.
Neuroscience. 1994 Oct;62(3):681-93. doi: 10.1016/0306-4522(94)90469-3.
Previous direct neurochemical studies of the temporal dynamics of cholinergic activation in the septohippocampal and nucleus basalis magnocellularis-cortical pathways at various stages during repeated testing of mice with selective spatial reference or working memory protocols [Durkin and Toumane (1992), Behav. Brain Res. 50, 43-52] showed that the post-test durations of cholinergic activation in each pathway varied as a function of the type of memory tested and the level of task mastery. Since (i) the hippocampal formation is considered to constitute a critical component of a temporary memory buffer, and (ii) working memory items are not thought to be submitted to consolidation and permanent storage, we postulated that the duration of testing-induced cholinergic activation in the septohippocampal pathway may govern the maintenance of the working memory trace over the retention interval. In order to test directly this hypothesis C57 B1/6 mice were extensively trained (one trial/day, 25-30 days) on an identical selective working memory task to attain high levels of retention (> 80% correct), but using either 5 min (Group 1), or 60 min (Group 2) retention intervals. At various times (30 s-75 min) following the initial acquisition phase of the test, cholinergic activity in the hippocampus and frontal cortex was quantified using measures of high-affinity choline uptake. Whereas cholinergic activation was observed in both pathways at 30 s post-acquisition and throughout the 5 min retention interval in Group 1, the situation in Group 2 is different, activation of the septohippocampal pathway being maintained for only 15 min, while activation in the nucleus basalis magnocellularis-cortical pathway is maintained for the totality of the 1 h retention interval. The nucleus basalis magnocellularis-cortical cholinergic pathway, in addition to its role in long-term reference memory storage processes may, thus, via an intervention in the temporal encoding of information, also subsume a complementary intermediate-term buffer storage role in working memory situations requiring retention intervals in excess of 15 min in mice. This secondary, "backup", function of the nucleus basalis magnocellularis-cortical pathway would thus liberate the septohippocampal complex from its primary active role in the temporary maintenance and/or accessibility of the working memory trace in these particular cases requiring long retention intervals.
先前对小鼠进行选择性空间参考或工作记忆实验的不同阶段，在隔海马和基底前脑大细胞 - 皮质通路中胆碱能激活的时间动态进行的直接神经化学研究[Durkin和Toumane（1992），《行为脑研究》50，43 - 52]表明，每条通路中胆碱能激活的测试后持续时间随所测试的记忆类型和任务掌握程度而变化。由于（i）海马结构被认为是临时记忆缓冲器的关键组成部分，且（ii）工作记忆项目不被认为会进行巩固和永久存储，我们推测隔海马通路中测试诱导的胆碱能激活持续时间可能在保持间隔内控制工作记忆痕迹的维持。为了直接验证这一假设，对C57 B1/6小鼠进行广泛训练（每天一次试验，25 - 30天），使其在相同的选择性工作记忆任务上达到高保持水平（> 80%正确），但分别使用5分钟（第1组）或60分钟（第2组）的保持间隔。在测试的初始习得阶段后的不同时间（30秒 - 75分钟），使用高亲和力胆碱摄取量来量化海马和额叶皮质中的胆碱能活性。在第1组中，习得后30秒及整个5分钟保持间隔内，两条通路均观察到胆碱能激活，而第2组的情况不同，隔海马通路的激活仅维持15分钟，而基底前脑大细胞 - 皮质通路的激活在整个1小时保持间隔内持续。因此，基底前脑大细胞 - 皮质胆碱能通路除了在长期参考记忆存储过程中的作用外，可能通过干预信息的时间编码，在小鼠需要超过15分钟保持间隔的工作记忆情况下，还承担互补的中期缓冲存储作用。因此，基底前脑大细胞 - 皮质通路的这种次要的“备用”功能将使隔海马复合体在这些需要长保持间隔的特定情况下，从其在工作记忆痕迹的临时维持和/或可及性方面的主要活跃作用中解放出来。
