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

本研究试图建立一种基于多对刺激的延迟非匹配样本任务的程序化和自动化方法，以测量大鼠的陈述性记忆。我们修改了一个经典的操作室，并在侧壁上配备了触摸屏，以便在每次试验中可以呈现各种二维模式。首先在中央窗口呈现一个样本刺激，当大鼠触摸它时，这个样本刺激消失了，经过一段延迟时间后，在左右两个窗口呈现两个不同的刺激，只有当大鼠选择了在样本期间没有出现的刺激时，才能用食物奖励反应。从研究中期开始，我们还测试了在三个窗口中的每一个下面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相同刺激对的程序，以及在每次试验中使用新刺激对的程序。然而，我们不能完全训练动物在不匹配的样本任务，无论延迟的长度。我们讨论了在操作室中训练大鼠不能很好地学习任务的原因。有几种可能性：大鼠可能不善于在短时间内辨别样本或选择刺激。大鼠可能很难很好地比较选择刺激。他们对左或右刺激的位置习惯可能会干扰正确的表现。进一步改进的任务程序，包括更好地选择所使用的刺激，在刺激过程中引入握杆的初步训练，并通过增加另一个杠杆在相对的墙壁上，使大鼠在两个墙壁之间来回。

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.