Woodruff-Pak Diana S, Disterhoft John F
Department of Psychology, Temple University, Philadelphia, PA 19122-6011, USA.
Trends Neurosci. 2008 Feb;31(2):105-12. doi: 10.1016/j.tins.2007.11.006. Epub 2008 Jan 15.
Intensive mapping of the essential cerebellar brain circuits for Pavlovian eyeblink conditioning appeared relatively complete by 2000, but new data indicate the need for additional differentiation of cerebellar regions and mechanisms coding delay and trace conditioning. This is especially important, as trace conditioning is an experimentally tractable model of declarative learning. The temporal gap in trace eyeblink conditioning may be bridged by forebrain regions through pontine-cerebellar nuclear connections that can bypass cerebellar cortex, whereas a cerebellar cortical long-term-depression-like process appears to be required to support normal delay conditioning. Experiments focusing on the role of cerebellar cortex and deep nuclei in delay versus trace conditioning add perspective on brain substrates of these seemingly similar paradigms, which differ only by a brief stimulus-free time gap between conditioned and unconditioned stimuli. This temporal gap appears to impose forebrain dependencies and differentially engage different cerebellar circuitry during acquisition of conditioned responses.
到2000年时，对巴甫洛夫式眨眼条件反射的基本小脑脑回路的密集映射似乎已相对完整，但新数据表明，需要对小脑区域以及编码延迟和痕迹条件反射的机制进行进一步区分。这一点尤为重要，因为痕迹条件反射是陈述性学习的一种实验上易于处理的模型。在痕迹眨眼条件反射中的时间间隙可能由前脑区域通过脑桥-小脑核连接来弥合，这种连接可以绕过小脑皮质，而小脑皮质类似长时程抑制的过程似乎是支持正常延迟条件反射所必需的。聚焦于小脑皮质和深部核团在延迟与痕迹条件反射中的作用的实验，为这些看似相似的范式的脑基质提供了新视角，它们之间的差异仅在于条件刺激和非条件刺激之间存在短暂的无刺激时间间隙。这个时间间隙似乎会在前脑产生依赖性，并在条件反应习得过程中使不同的小脑回路产生不同的参与情况。
