Research for brain mechanism of visual and auditory memory in rats

研究表明，大鼠对听觉信息的反应比视觉信息有更强的短期记忆（例如，Tsutsui, 1998）。这种现象被称为记忆的模态效应。本研究探讨了大鼠脑内胆碱能通路与模态效应的关系。18只大鼠被训练执行连续延迟匹配样本（SDMTS）任务，使用两个可伸缩杠杆的操作室。配对刺激（S1-S2）被分为1秒、3秒或5秒的延迟间隔。S1和S2的组合类型分别为Light-Light、Light-Tone、Tone-Tone和Tone-Light。大鼠必须根据刺激的组合按下两个杠杆中的一个：当S1的模态与S2的模态相同时，按下右边的杠杆就会得到食物颗粒的奖励，当S1的模态与S2的模态不同时，按下左边的杠杆就会得到同样的奖励。获得SDMTS后，一半大鼠单侧切除Meynert基底核（nbm），另一半大鼠行假手术。nbm的损伤破坏了听觉信息的保留，作为S1和S2之间延迟间隔长度的函数。无论延迟间隔的长短，nbm被破坏的大鼠都不能保留视觉信息。因此，根据记忆信息的形态，nbm具有两种不同的作用。nbm可能与听觉信息的短期记忆和视觉信息的长期记忆有关。

Studies have shown that rats have a greater short-term memory in response to auditory information over visual information (ex. Tsutsui, 1998). This phenomenon is known as the modality effect on memory. In this study, the relationship between the modality effect and cholinergic pathways was examined in rats brains. Eighteen rats were trained to perform a successive delayed matching-to-sample (SDMTS) task, using operant chambers with two retractable levers. Paired stimuli (S1-S2), which was divided by a delay interval of 1 second, 3 seconds, or 5 seconds, was presented to the animals. The four types of S1 and S2 combinations were as follows : Light-Light, Light-Tone, Tone-Tone, and Tone-Light. The rats had to press one of the two levers depending on the combination of the stimuli : When the modality of S1 was identical to that of S2, pressing the right lever was rewarded with a food pellet, and when the modality of S1 was different from that of S2, pressing the left lever was rewarded in the same manner. After the acquisition of the SDMTS, half of the rats were given a lesion into the nucleus basalis of Meynert (nbm) unilaterally, and the other half received a sham operation. Lesions given to the nbm disrupted the retention of auditory information, as a function of the length of the delay interval between S1 and S2. Rats whose nbm was destroyed were not able to retain visual information irrespective of the length of the delay interval. As a result, it has been suggested that the nbm has two different roles according to the modality of memory information. There is a possibility that the nbm is related to the short-term memory of auditory information and to the long-term memory of visual information.