Plakke Bethany, Freeman John H, Poremba Amy
Department of Psychology, University of Iowa, E11 SSH, Iowa City, IA 52242, USA.
Neurobiol Learn Mem. 2007 Jul;88(1):11-8. doi: 10.1016/j.nlm.2007.03.008. Epub 2007 Apr 30.
The essential neural circuitry for delay eyeblink conditioning has been largely identified, whereas much of the neural circuitry for trace conditioning has not been identified. The major difference between delay and trace conditioning is a time gap between the presentation of the conditioned stimulus (CS) and the unconditioned stimulus (US) during trace conditioning. It is this time gap or trace interval which accounts for an additional memory component in trace conditioning. Additional neural structures are also necessary for trace conditioning, including hippocampus and prefrontal cortex. This addition of forebrain structures necessary for trace but not delay conditioning suggests other brain areas become involved when a memory gap is added to the conditioning parameters. A metabolic marker of energy use, radioactively labeled glucose analog, was used to compare differences in glucose analog uptake between delay, trace, and unpaired experimental groups in order to identify new areas of involvement within the cerebellum. Known structures such as the interpositus nucleus and lobule HVI showed increased activation for both delay and trace conditioning compared to unpaired conditioning. However, there was a differential amount of activation between anterior and posterior portions of the interpositus nucleus between delay and trace, respectively. Cerebellar cortical areas including lobules IV and V of anterior lobe, Crus I, Crus II, and paramedian lobule also showed increases in activity for delay conditioning but not for trace conditioning. Delay and trace eyeblink conditioning both resulted in increased metabolic activity within the cerebellum but delay conditioning resulted in more widespread cerebellar cortical activation.
延迟性眨眼条件反射的基本神经回路已基本明确，而痕迹条件反射的大部分神经回路尚未明确。延迟性条件反射和痕迹条件反射之间的主要区别在于，在痕迹条件反射中，条件刺激（CS）和非条件刺激（US）呈现之间存在时间间隔。正是这个时间间隔或痕迹间隔导致了痕迹条件反射中额外的记忆成分。痕迹条件反射还需要其他神经结构，包括海马体和前额叶皮质。痕迹条件反射而非延迟性条件反射所必需的前脑结构的增加表明，当在条件反射参数中加入记忆间隔时，其他脑区也会参与进来。使用一种能量利用的代谢标记物，即放射性标记的葡萄糖类似物，来比较延迟性、痕迹性和非配对实验组之间葡萄糖类似物摄取的差异，以便确定小脑内新的参与区域。与非配对条件反射相比，已知结构如间位核和小叶HVI在延迟性和痕迹性条件反射中均显示出激活增加。然而，间位核的前部和后部在延迟性和痕迹性条件反射之间分别存在不同程度的激活。小脑皮质区域，包括前叶的小叶IV和V、 Crus I、Crus II和旁正中小叶，在延迟性条件反射中也显示出活动增加，但在痕迹性条件反射中没有。延迟性和痕迹性眨眼条件反射均导致小脑内代谢活动增加，但延迟性条件反射导致更广泛的小脑皮质激活。
