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

在这项研究中，我们试图发展使用多对刺激的延迟不匹配到样本任务的程序化和自动化，以测量大鼠的陈述性记忆。我们改装了一个经典的手术室，在侧壁上配备了一个触摸屏，以便在每次试验中都能呈现各种二维图案。一个样本刺激首先出现在中心窗口，当老鼠触摸它时，这个刺激消失了。在一段延迟期后，左右两个窗口出现两种不同的刺激，只有当大鼠选择了样本期内没有出现的刺激时，反应才会得到食物奖励。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，以避免不稳定地检测到大鼠的反应。我们测试了重复使用相同的刺激对以及在每次试验中使用新的刺激对的程序。然而，无论延迟有多长，我们都不能在不匹配到样本的任务中完全训练动物。我们讨论了为什么大鼠在手术室训练时不能很好地学习这项任务。有几种可能性：老鼠可能不擅长在短时间内辨别样品或选择刺激。对于老鼠来说，很难很好地比较这些选择刺激。他们对右或左刺激表现出的姿势习惯可能会干扰正确的表现。提出了进一步改进的任务程序，包括更好地选择所使用的刺激，引入在刺激时握住杠杆的初步训练，以及通过在相对的墙上增加另一个杠杆来使大鼠在两面墙之间来回走动。

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.