Bang Sun Jung, Brown Thomas H
Departments of Psychology and Cellular and Molecular Physiology, Yale University, New Haven, CT 06520, USA.
J Neurosci. 2009 Apr 8;29(14):4346-50. doi: 10.1523/JNEUROSCI.0069-09.2009.
Trace conditioning requires that a transient representation of the conditional stimulus (CS) persists during the time interval between the CS offset and the onset of the unconditional stimulus. According to one hypothesis, this transient CS representation is supported by endogenous activity in "persistent-firing" neurons of perirhinal cortex (PR). By definition, persistent-firing neurons discharge for tens of seconds or minutes after the termination of the original spike-initiating stimulus. This continued spiking does not depend on recurrent circuit activity and can be reliably and completely blocked by muscarinic receptor antagonists. The present study evaluated the role of PR muscarinic receptors in trace fear conditioning. Before conditioning, rats received bilateral intra-PR infusions with either saline or scopolamine, a nonselective muscarinic receptor antagonist. Scopolamine infusions profoundly impaired trace conditioning but had no effect on delay conditioning or context conditioning. The results encourage a more general understanding of muscarinic receptors in PR and they motivate additional tests of the emerging theory that persistent-firing neurons support aspects of transient memory.
痕迹条件作用要求条件刺激（CS）的短暂表征在CS消失与无条件刺激开始之间的时间间隔内持续存在。根据一种假设，这种短暂的CS表征由内嗅皮层（PR）“持续放电”神经元的内源性活动支持。根据定义，持续放电神经元在原始引发动作电位的刺激终止后会放电数十秒或数分钟。这种持续的放电不依赖于循环回路活动，并且可以被毒蕈碱受体拮抗剂可靠且完全地阻断。本研究评估了PR毒蕈碱受体在痕迹恐惧条件作用中的作用。在条件作用前，大鼠接受双侧PR内注射生理盐水或东莨菪碱（一种非选择性毒蕈碱受体拮抗剂）。注射东莨菪碱严重损害了痕迹条件作用，但对延迟条件作用或情境条件作用没有影响。这些结果促进了对PR中毒蕈碱受体的更全面理解，并激发了对持续放电神经元支持短暂记忆方面这一新兴理论的更多测试。
