Staubli U, Schottler F, Nejat-Bina D
Center for the Neurobiology of Learning and Memory, University of California, Irvine 92717.
Behav Brain Res. 1987 Aug;25(2):117-29. doi: 10.1016/0166-4328(87)90005-2.
Four experiments were conducted to characterize the role of primary and secondary olfactory projection areas (piriform cortex and dorsomedial thalamic nucleus (DMN] in olfactory information processing. Rats had to learn to discriminate between odors that were simultaneously released from different arms of an automated olfactory maze. When standard training conditions were used, damage of the DMN severely impaired both preoperatively trained and naive animals in acquiring an odor discrimination set (i.e. in most problems no learning was demonstrated). An additional group of DMN animals that received 4 times the standard amount of daily trials was unable to acquire the first two problems but successfully solved the third and all subsequent discriminations. Analysis of performance patterns suggested that destruction of the DMN initially leads to a strong procedural impairment that can be overcome by extensive training. After solving the third problem the animals with DMN damage required much less training to reach the learning criterion but generally made more errors than controls. Transfer of savings rarely occurred when a problem was repeated. Whether this secondary learning deficit observed in later discriminations is due to a specific effect of the lesion on the encoding of olfactory cues and thus on memory formation, or due to a disturbance in the regulation of emotional factors such as motivation, arousal, and attention is discussed. Lesions of the thalamus that spared the DMN had no effect on learning or retention of olfactory discriminations. Animals with ablations of the piriform cortex only acquired odor discriminations if they had been trained in the olfactory maze before the lesion. Moreover, their performance depended on the odor quality: they had great difficulty learning complex cues consisting of several odorants and learned simple odors virtually identical to control rats. The results indicate that an intact piriform cortex is needed to acquire the procedures involved to perform an olfactory discrimination task as well as to build neural representations of olfactory cues.
进行了四项实验，以确定初级和次级嗅觉投射区域（梨状皮质和背内侧丘脑核（DMN））在嗅觉信息处理中的作用。大鼠必须学会区分从自动嗅觉迷宫不同臂同时释放的气味。当使用标准训练条件时，DMN损伤严重损害了术前训练的动物和未经过训练的动物获得气味辨别组的能力（即，在大多数问题中未表现出学习）。另一组接受四倍标准日试验量的DMN动物无法解决前两个问题，但成功解决了第三个及所有后续辨别问题。对表现模式的分析表明，DMN的破坏最初会导致强烈的程序障碍，这种障碍可以通过广泛训练来克服。解决第三个问题后，患有DMN损伤的动物达到学习标准所需的训练要少得多，但通常比对照组犯更多错误。当重复一个问题时，节省的迁移很少发生。讨论了在后期辨别中观察到的这种二次学习缺陷是由于病变对嗅觉线索编码以及记忆形成的特定影响，还是由于动机、唤醒和注意力等情绪因素调节的干扰。保留DMN的丘脑损伤对嗅觉辨别学习或记忆没有影响。仅切除梨状皮质的动物只有在损伤前在嗅觉迷宫中接受过训练才能获得气味辨别能力。此外，它们的表现取决于气味质量：它们在学习由几种气味剂组成的复杂线索时非常困难，而学习简单气味时与对照大鼠几乎相同。结果表明，完整的梨状皮质是获取执行嗅觉辨别任务所需程序以及构建嗅觉线索神经表征所必需的。
