Shakhawat Amin M D, Gheidi Ali, MacIntyre Iain T, Walsh Melissa L, Harley Carolyn W, Yuan Qi
Division of Biomedical Sciences, Faculty of Medicine, and.
Department of Psychology, Faculty of Science, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3V6, Canada.
J Neurosci. 2015 Oct 14;35(41):14070-5. doi: 10.1523/JNEUROSCI.2690-15.2015.
Arc ensembles in adult rat olfactory bulb (OB) and anterior piriform cortex (PC) were assessed after discrimination training on highly similar odor pairs. Nonselective α- and β-adrenergic antagonists or saline were infused in the OB or anterior PC during training. OB adrenergic blockade slowed, but did not prevent, odor discrimination learning. After criterion performance, Arc ensembles in anterior piriform showed enhanced stability for the rewarded odor and pattern separation for the discriminated odors as described previously. Anterior piriform adrenergic blockade prevented acquisition of similar odor discrimination and of OB ensemble changes, even with extended overtraining. Mitral and granule cell Arc ensembles in OB showed enhanced stability for rewarded odor only in the saline group. Pattern separation was not seen in the OB. Similar odor discrimination co-occurs with increased stability in rewarded odor representations and pattern separation to reduce encoding overlap. The difficulty of similar discriminations may relate to the necessity to both strengthen rewarded representations and weaken overlap across similar representations.
We show for the first time that adrenoceptors in anterior piriform cortex (aPC) must be engaged for adult rats to learn to discriminate highly similar odors. Loss of adrenergic activation in olfactory bulb (OB) slows, but does not prevent, discrimination learning. Both increased stability of the rewarded odor representation and increased pattern separation of the rewarded and unrewarded odors in aPC accompany successful discrimination. In the OB, rewarded odors increase in ensemble stability, but there is no evidence of pattern separation. We suggest that the slow acquisition of similar odor discriminations is related to the differing plasticity requirements for increased stability and pattern separation.
在对高度相似的气味对进行辨别训练后，评估成年大鼠嗅球（OB）和前梨状皮质（PC）中的Arc集合。在训练期间，将非选择性α和β肾上腺素能拮抗剂或生理盐水注入OB或前PC。OB肾上腺素能阻断减缓了但并未阻止气味辨别学习。达到标准表现后，如前所述，前梨状皮质中的Arc集合对奖励气味表现出增强的稳定性，对辨别出的气味表现出模式分离。前梨状皮质肾上腺素能阻断阻止了相似气味辨别以及OB集合变化的获得，即使进行了延长的过度训练。仅在生理盐水组中，OB中的二尖瓣和颗粒细胞Arc集合对奖励气味表现出增强的稳定性。在OB中未观察到模式分离。相似气味辨别与奖励气味表征稳定性增加以及模式分离同时出现，以减少编码重叠。相似辨别的困难可能与加强奖励表征和削弱相似表征之间的重叠的必要性有关。
我们首次表明，成年大鼠要学会辨别高度相似的气味，前梨状皮质（aPC）中的肾上腺素能受体必须参与其中。嗅球（OB）中肾上腺素能激活的丧失减缓了但并未阻止辨别学习。成功辨别伴随着aPC中奖励气味表征稳定性的增加以及奖励和未奖励气味模式分离的增加。在OB中，奖励气味的集合稳定性增加，但没有模式分离的证据。我们认为，相似气味辨别的缓慢获得与稳定性增加和模式分离的不同可塑性要求有关。
