Robinson Siobhan, Keene Christopher S, Iaccarino Hannah F, Duan Daisy, Bucci David J
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, NH 03755, USA.
Behav Neurosci. 2011 Aug;125(4):578-87. doi: 10.1037/a0024262.
The retrosplenial cortex (RSP) is highly interconnected with medial temporal lobe structures, yet relatively little is known about its specific contributions to learning and memory. One possibility is that RSP is involved in forming associations between multiple sensory stimuli. Indeed, damage to RSP disrupts learning about spatial or contextual cues and also impairs learning about co-occurring conditioned stimuli (CSs). Two experiments were conducted to test this notion more rigorously. In Experiment 1, rats were trained in a serial feature negative discrimination task consisting of reinforced presentations of a tone alone and nonreinforced serial presentations of a light followed by the tone. Thus, in contrast to prior studies, this paradigm involved serial presentation of conditioned stimuli (CS), rather than simultaneous presentation. Rats with damage to RSP failed to acquire the discrimination, indicating that RSP is required for forming associations between sensory stimuli regardless of whether they occur serially or simultaneously. In Experiment 2, a sensory preconditioning task was used to determine if RSP was necessary for forming associations between stimuli even in the absence of reinforcement. During the first phase of this procedure, one auditory stimulus was paired with a light while a second auditory stimulus was presented alone. In the next phase of training, the same light was paired with food. During the final phase of the procedure both auditory stimuli were presented alone during a single session. Control, but not RSP-lesioned rats, exhibited more food cup behavior following presentation of the auditory cue that was previously paired with light compared with the unpaired auditory stimulus, indicating that a stimulus-stimulus association was formed during the first phase of training. These results support the idea that RSP has a fundamental role in forming associations between environmental stimuli.
压后皮质（RSP）与内侧颞叶结构高度互连，但对于其对学习和记忆的具体贡献却知之甚少。一种可能性是，RSP参与了多种感觉刺激之间关联的形成。的确，RSP损伤会破坏对空间或情境线索的学习，也会损害对同时出现的条件刺激（CS）的学习。进行了两项实验以更严格地检验这一观点。在实验1中，大鼠接受了一系列特征性负性辨别任务的训练，该任务包括单独呈现声音时给予强化，以及先呈现灯光再呈现声音时不给予强化。因此，与先前的研究不同，该范式涉及条件刺激（CS）的系列呈现，而非同时呈现。RSP损伤的大鼠未能习得这种辨别，这表明无论感觉刺激是系列出现还是同时出现，RSP都是形成它们之间关联所必需的。在实验2中，使用了一种感觉预适应任务来确定即使在没有强化的情况下，RSP对于形成刺激之间的关联是否必要。在该程序的第一阶段，一个听觉刺激与一个灯光配对，而另一个听觉刺激单独呈现。在训练的下一阶段，相同的灯光与食物配对。在程序的最后阶段，在单个实验环节中单独呈现两个听觉刺激。与未配对的听觉刺激相比，对照组大鼠（而非RSP损伤组大鼠）在呈现先前与灯光配对的听觉线索后表现出更多的舔食行为，这表明在训练的第一阶段形成了刺激-刺激关联。这些结果支持了RSP在形成环境刺激之间的关联中具有基本作用这一观点。
