Hasselmo M E, Schnell E, Barkai E
Department of Psychology, Harvard University, Cambridge, Massachusetts 02138, USA.
J Neurosci. 1995 Jul;15(7 Pt 2):5249-62. doi: 10.1523/JNEUROSCI.15-07-05249.1995.
Hippocampal region CA3 contains strong recurrent excitation mediated by synapses of the longitudinal association fibers. These recurrent excitatory connections may play a dominant role in determining the information processing characteristics of this region. However, they result in feedback dynamics that may cause both runaway excitatory activity and runaway synaptic modification. Previous models of recurrent excitation have prevented unbounded activity using biologically unrealistic techniques. Here, the activation of feedback inhibition is shown to prevent unbounded activity, allowing stable activity states during recall and learning. In the model, cholinergic suppression of synaptic transmission at excitatory feedback synapses is shown to determine the extent to which activity depends upon new features of the afferent input versus components of previously stored representations. Experimental work in brain slice preparations of region CA3 demonstrates the cholinergic suppression of synaptic transmission in stratum radiatum, which contains synapses of the longitudinal association fibers.
海马体CA3区包含由纵向联合纤维突触介导的强烈的反复兴奋。这些反复的兴奋性连接可能在决定该区域的信息处理特性方面起主导作用。然而，它们会导致反馈动力学，这可能会引起失控的兴奋性活动和失控的突触修饰。以前的反复兴奋模型使用生物学上不现实的技术来防止无界活动。在这里，反馈抑制的激活被证明可以防止无界活动，从而在回忆和学习过程中允许稳定的活动状态。在该模型中，胆碱能对兴奋性反馈突触处突触传递的抑制被证明可以决定活动依赖于传入输入的新特征与先前存储表征的成分的程度。在CA3区脑片制备中的实验工作证明了放射层中突触传递的胆碱能抑制，放射层包含纵向联合纤维的突触。
