Study on declarative memory in rats using delayed nonmatching-to-sample task : role of hippocampal glutamate receptors

在本研究中，我们试图利用多对刺激发展延迟非匹配-样本任务的程序和自动化，以测量大鼠的陈述性记忆。我们对一个经典的手术腔进行了改进，在侧壁安装了触摸屏，使每次试验都能呈现各种二维图案。首先在中央窗口呈现一个样本刺激，当大鼠触摸它时，这个刺激就消失了。在一段延迟期后，在左右两个窗口分别呈现两种不同的刺激，只有当大鼠选择了没有出现在样本期的刺激时，才会得到食物奖励。从研究中期开始，我们还测试了在三个窗口下面分别放置三个杠杆的装置，而不是触摸屏装置，以避免对大鼠反应的不稳定检测。我们测试了重复使用同一对刺激的过程，以及每次试验都使用新对刺激的过程。然而，无论延迟时间长短，我们都不能完全训练动物的非匹配样本任务。我们讨论了为什么大鼠在操作室内训练时不能很好地学习任务。有几种可能性：大鼠可能不擅长在短时间内区分样本或选择刺激。对于大鼠来说，很好地比较选择刺激可能是困难的。他们表现出的向右或向左刺激的位置习惯可能会干扰正确的表现。进一步改进任务程序，包括更好地选择使用的刺激，在刺激过程中引入握住杠杆的初步训练，以及通过在对面的墙上增加另一个杠杆使大鼠在两面墙之间来回移动。

In this study we tried to develop the procedures and automatization of delayed nonmatching-to-sample task using multiple pairs of stimuli in order to measure declarative memory in rats. We modified a classical operant chamber and equipped it with a touch screen on a side wall so that various two-dimensional patterns could be presented in each trial. A sample stimulus was presented in the center window first, and this disappeared when the rat touched it. After a delay period two different stimuli were presented in the left and right windows, and the response was rewarded with food only when the rat selected the stimulus that did not appear in the sample period. From the middle of the study, we also tested the apparatus in which three levers were put below each of the three windows instead of touch screen apparatus in order to avoid the unstable detection of rats' responses. We tested the procedure in which the same pair of stimuli were repeatedly used as well as the one in which new pairs were used in every trial. However we could not fully train animals in the nonmatching-to-sample task regardless of the length of delay. We discussed why rats can not learn well the task when they were trained in the operant chamber. There are several possibilities : rats may not be good at discriminating the sample or choice stimuli within a short period. It may be difficult for rats to compare the choice stimuli well. Position habit that they show to the right or left stimuli may disturb the correct performance. Further improvement of the task procedures including the better selection of the stimuli used, introducing preliminary training of holding the lever during stimuli are presented, and making rats go back and forth between two walls by adding another lever on the opposite wall are expected.