Klement Daniel, Past'alková Eva, Fenton André A
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Hippocampus. 2005;15(4):460-71. doi: 10.1002/hipo.20072.
The hippocampus is critical for navigation in an open field. One component of this navigation requires the subject to recognize the target place using distal cues. The experiments presented in this report tested whether blocking hippocampal function would impair open field place recognition. Hungry rats were trained to press a lever on a feeder for food. In Experiment 1, they were passively transported with the feeder along a circular trajectory. Lever pressing was reinforced only if the feeder was passing through a 60 degrees -wide sector. Thus, rats preferentially lever pressed in the vicinity of the reward sector indicating that they recognized its location. Tetrodotoxin (TTX) infusions aimed at the dorsal hippocampi caused rats to substantially increase lever pressing with no preference for any region. The aim of Experiment 2 was to determine whether the TTX injections caused a loss of place recognition or a general increase of lever pressing. A separate group of rats was conditioned in a stationary apparatus to press the lever in response to a light. The TTX injections did not abolish preferential lever pressing in response to light. Lever pressing increased less than half as much as the TTX-induced increase in Experiment 1. When these animals with functional hippocampi could not determine the rewarded period because the light was always off, lever pressing increased much more and was similar to the TTX-induced increase in Experiment 1. We conclude that the TTX inactivation of the hippocampi impaired the ability to recognize the reward place.
海马体对于在开阔场地中的导航至关重要。这种导航的一个组成部分要求主体使用远处的线索来识别目标位置。本报告中呈现的实验测试了阻断海马体功能是否会损害开阔场地位置识别能力。饥饿的大鼠被训练按压喂食器上的杠杆以获取食物。在实验1中，它们被带着喂食器沿圆形轨迹被动运输。只有当喂食器经过一个60度宽的扇形区域时，按压杠杆才会得到强化。因此，大鼠在奖励扇形区域附近优先按压杠杆，这表明它们识别出了其位置。向背侧海马体注射河豚毒素（TTX）导致大鼠大幅增加杠杆按压次数，且对任何区域都没有偏好。实验2的目的是确定TTX注射是导致位置识别丧失还是杠杆按压普遍增加。另一组大鼠在固定装置中接受训练，以在光照时按压杠杆。TTX注射并没有消除对光照的优先杠杆按压。杠杆按压次数的增加不到实验1中TTX诱导增加量的一半。当这些具有功能正常海马体的动物由于光照一直关闭而无法确定奖励期时，杠杆按压次数增加得更多，且与实验1中TTX诱导的增加量相似。我们得出结论，海马体的TTX失活损害了识别奖励位置的能力。
