Gibbs C M, Prescott L B, Powell D A
Neuroscience Laboratory, Dorn Veterans Medical Center, Columbia, SC.
Exp Brain Res. 1992;89(3):599-610. doi: 10.1007/BF00229885.
Multiple-unit activity (MUA) was recorded from chronically implanted electrodes in the medial prefrontal cortex (PFCm) and the agranular insular cortex (Iag) in separate groups of rabbits during habituation training, followed by aversive Pavlovian conditioning and subsequent extinction training. Control animals received explicitly unpaired presentations of the tone conditioned stimulus (CS) and eye-shock unconditioned stimulus (US). Both the cardiac orientating reflex and the conditioned heart rate response (HR CR) consisted of bradycardia, whereas tone-evoked tachycardia was observed in animals that received unpaired stimuli. Short-latency (less than 20-60 ms), tone-evoked increases in PFCm MUA were observed during the initial trials of habituation training, with their magnitude declining predictably across repeated tone-alone presentations. Subsequent CS/US pairings, however, served systematically to reinstate and enhance this CS-evoked MUA, while both non-associative (unpaired CS/US) and extinction (CS alone) training resulted in significant attenuation of such activity. Unconditioned tone-evoked increases in MUA were also observed in the Iag during habituation; however, such unit responses appeared to be more variable than their PFCm counterparts and were of considerably lesser magnitude. Moreover, in striking contrast to the above PFCm findings, conditioning and non-associative training did not differentially affect overall mean evoked MUA in the Iag, although different post-tone patterns of activity were obtained with the two procedures. The contrasting training effects observed in animals with PFCm vs. Iag electrode placements did not appear to be attributable to differences in regional sensitivity to the US, since excitatory patterns of MUA were elicited by unsignalled presentations of eye-shock at most placements within each cortical field. Accordingly, the present findings are consistent with our previous lesion data in suggesting that, although training-induced changes in PFCm neuronal activity may contribute to the initial events in aversive Pavlovian conditioning, an involvement of the Iag in such processes, if any, remains to be demonstrated.
在习惯化训练、厌恶性巴甫洛夫条件反射及随后的消退训练过程中，分别对不同组家兔内侧前额叶皮质（PFCm）和无颗粒岛叶皮质（Iag）中慢性植入电极记录的多单位活动（MUA）进行了研究。对照动物接受了明确的非配对呈现，即条件刺激音（CS）和眼部电击非条件刺激（US）。心脏定向反射和条件性心率反应（HR CR）均表现为心动过缓，而在接受非配对刺激的动物中观察到音调诱发的心动过速。在习惯化训练的初始试验中，观察到PFCm MUA出现短潜伏期（小于20 - 60毫秒）的音调诱发增加，其幅度在单独重复呈现音调时可预测地下降。然而，随后的CS/US配对系统性地恢复并增强了这种CS诱发的MUA，而非关联性（非配对CS/US）和消退（单独CS）训练均导致此类活动显著减弱。在习惯化过程中，Iag中也观察到非条件性音调诱发的MUA增加；然而，此类单位反应似乎比PFCm中的反应更具变异性，且幅度要小得多。此外，与上述PFCm的发现形成鲜明对比的是，尽管两种程序获得了不同的音调后活动模式，但条件反射和非关联性训练对Iag中总体平均诱发MUA没有差异影响。在PFCm与Iag电极植入动物中观察到的对比性训练效果似乎并非归因于各皮质区域对US的敏感性差异，因为在每个皮质区域的大多数植入部位，无信号的眼部电击呈现均可诱发MUA的兴奋性模式。因此，本研究结果与我们之前的损伤数据一致，表明尽管训练诱导的PFCm神经元活动变化可能有助于厌恶性巴甫洛夫条件反射的初始事件，但Iag在此类过程中的参与（如果有的话）仍有待证实。
