Department of Neuroscience, Brown University, Providence, RI, USA.
Hippocampus. 2012 Oct;22(10):2059-67. doi: 10.1002/hipo.22063.
Rats with combined lesions of the perirhinal (PER) and postrhinal (POR) cortices were trained on a complex discrimination in the simultaneous feature-positive and feature-negative discrimination task. In this task, a panel light (L) paired with an auditory stimulus determined whether a tone (T) or white noise (N) would be rewarded (+) or not rewarded (-). Thus, the light feature determined whether the target auditory stimuli were rewarded or not. In each session, trial types were LT+, T-, N+, and LN-. We had hypothesized that damage to the target regions would impair performance on this task. Acquisition was altered in the lesioned rats, but not in the predicted direction. Instead, lesioned rats exhibited significantly enhanced acquisition of the discrimination. Manipulation of intertrial intervals indicated that reduction of proactive interference did not explain the enhancement. Lesioned rats were not different from controls on a multiple-cued interval timing task, providing evidence that the enhancement does not extend to all types of discriminations and is not due to a deficit in timing. Other research shows that rats with PER lesions are impaired on similar tasks, thus the enhancement is likely due to the effects of POR damage. Normally in this task, context is thought to accrue inhibitory control over other cues. Without this inhibitory control, animals might be expected to learn the task more efficiently. Our conclusion is that deficits in processing contextual information underlie the enhanced acquisition observed in rats with combined PER and POR damage on this complex discrimination task.
双侧前额叶（PER）和后前额叶（POR）皮质联合损伤的大鼠在同时具有特征阳性和特征阴性的辨别任务中接受了复杂辨别训练。在这个任务中，面板灯光（L）与听觉刺激配对，决定了音调（T）或白噪声（N）是否会得到奖励（+）或不奖励（-）。因此，光特征决定了目标听觉刺激是否得到奖励。在每次试验中，试验类型为 LT+、T-、N+ 和 LN-。我们假设目标区域的损伤会损害大鼠在该任务上的表现。损伤大鼠的获得性发生了改变，但不是朝着预测的方向改变。相反，损伤大鼠在辨别学习上表现出明显增强的获得能力。试验间间隔的操纵表明，主动干扰的减少并不能解释这种增强。损伤大鼠在多项线索间隔定时任务上与对照组没有差异，这表明这种增强并不扩展到所有类型的辨别，也不是由于定时缺陷所致。其他研究表明，PER 损伤的大鼠在类似的任务上表现受损，因此这种增强可能是由于 POR 损伤的影响。在正常情况下，在这个任务中，背景被认为对其他线索施加了抑制性控制。没有这种抑制性控制，动物可能会更有效地学习任务。我们的结论是，在双侧前额叶和后前额叶皮质联合损伤的大鼠在这个复杂的辨别任务中，对上下文信息的处理缺陷导致了观察到的获得能力增强。
