Department of Psychology and Neuroscience Program, Washington and Lee University, Lexington, Virginia 24450, USA.
Hippocampus. 2012 Apr;22(4):680-92. doi: 10.1002/hipo.20928. Epub 2011 Apr 27.
This study examined structural-functional differences along the septo-temporal axis of hippocampus using radial-maze tasks that involved two different memory processes [reference memory (RM) and working memory (WM)], and the use of two kinds of information (spatial vs. nonspatial cue learning). In addition, retention of the nonspatial cue task was tested nine weeks following completion of acquisition, and the rats then underwent discrimination reversal training. Ibotenic acid lesions limited to either the dorsal pole, intermediate area, or ventral pole had minimal effects on acquisition of the complex place and cue discrimination tasks. The one exception was that rats with lesions confined to the dorsal third of hippocampus made more WM errors on the spatial task (but not the cue task) early in training. Selective lesions of the three hippocampal regions had no effects on either long-term retention or reversal of the nonspatial cue discrimination task. In contrast, rats that had all of the hippocampus removed were severely impaired in learning the spatial task, making many RM and WM errors, whereas on the nonspatial cue task, the impairment was limited to WM errors. Further analysis of the WM errors made in acquisition showed that rats with complete lesions were significantly more likely on both the spatial and nonspatial cue tasks to reenter arms that had been baited and visited on that trial compared to arms that had not been baited. A similar pattern of errors emerged for complete hippocampal lesioned rats during reversal discrimination. This pattern of errors suggests that in addition to an impairment in handling spatial information, complete removal of hippocampus also interferes with the ability to inhibit responding to cues that signal reward under some conditions but not under others. The finding that selective lesions limited to the intermediate zone of the hippocampus produce no impairment in either WM ("rapid place learning") or RM in our radial maze tasks serve to limit the generality of the conclusion of Bast et al. (Bast et al. (2009) PLos Biol 7:730-746) that the intermediate area is needed for behavioral performance based on rapid learning about spatial cues.
这项研究使用涉及两种不同记忆过程（参考记忆（RM）和工作记忆（WM））和两种信息（空间与非空间线索学习）的放射状迷宫任务，研究了海马沿隔颞轴的结构功能差异。此外，在获得完成后 9 周测试了非空间线索任务的保留情况，然后大鼠接受辨别反转训练。局限于背极、中间区或腹极的烟碱酸损伤对复杂位置和线索辨别任务的获得几乎没有影响。一个例外是，海马背三分之一损伤的大鼠在训练早期的空间任务（但不是线索任务）上犯了更多的 WM 错误。海马三个区域的选择性损伤对非空间线索辨别任务的长期保留或反转均无影响。相比之下，所有海马切除的大鼠在学习空间任务时严重受损，犯了许多 RM 和 WM 错误，而在非空间线索任务中，损害仅限于 WM 错误。对获得过程中 WM 错误的进一步分析表明，完全损伤的大鼠在空间和非空间线索任务上，与未诱饵的臂相比，更有可能重新进入该试验中诱饵和访问过的臂。在反转辨别过程中，完全海马损伤大鼠也出现了类似的错误模式。这种错误模式表明，除了在处理空间信息方面的障碍外，完全去除海马还会干扰在某些条件下抑制对信号奖励的线索做出反应的能力，而在其他条件下则不会。选择性局限于海马中间区的损伤不会导致我们的放射状迷宫任务中的 WM（“快速位置学习”）或 RM 受损的发现，限制了 Bast 等人（Bast 等人（2009 年）PLoS Biol 7:730-746）的结论的普遍性，即中间区是基于快速学习空间线索进行行为表现所必需的。
