Pelletier Joe Guillaume, Apergis John, Paré Denis
Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, New Jersey 07102, USA.
J Neurophysiol. 2004 May;91(5):2079-89. doi: 10.1152/jn.01197.2003.
One model of episodic memory posits that during slow-wave sleep (SWS), the synchronized discharges of hippocampal neurons in relation to sharp waves "replay" activity patterns that occurred during the waking state, facilitating synaptic plasticity in the neocortex. Although evidence of replay was found in the hippocampus in relation to sharp waves, it was never shown that this activity reached the neocortex. Instead, it was assumed that the rhinal cortices faithfully transmit information from the hippocampus to the neocortex and reciprocally. Here, we tested this idea using 3 different approaches. 1) Stimulating electrodes were inserted in the entorhinal cortex and temporal neocortex and evoked unit responses were recorded in between them, in the intervening rhinal cortices. In these conditions, impulse transfer occurred with an extremely low probability, in both directions. 2) To rule out the possibility that this unreliable transmission resulted from the artificial nature of electrical stimuli, crosscorrelation analyses of spontaneous neocortical, perirhinal, and entorhinal firing were performed in unanesthetized animals during the states of waking and SWS. Again, little evidence of propagation could be obtained in either state. 3) To test the idea that propagation occurs only when large groups of neurons are activated within a narrow time window, we computed perievent histograms of neocortical, perirhinal, and entorhinal neuronal discharges around large-amplitude sharp waves. However, these synchronized entorhinal discharges also failed to propagate across the perirhinal cortex. These findings suggest that the rhinal cortices are more than a relay between the neocortex and hippocampus, but rather a gate whose properties remain to be identified.
一种情景记忆模型假定，在慢波睡眠（SWS）期间，海马神经元与尖波相关的同步放电“重演”清醒状态下出现的活动模式，促进新皮层中的突触可塑性。尽管在海马体中发现了与尖波相关的重演证据，但从未表明这种活动能到达新皮层。相反，人们认为鼻周皮质忠实地将信息从海马体传递到新皮层，并进行反向传递。在此，我们使用3种不同方法对这一观点进行了测试。1）将刺激电极插入内嗅皮质和颞叶新皮层，并在其间的鼻周皮质记录诱发的单位反应。在这些条件下，脉冲双向传递的概率极低。2）为排除这种不可靠传递是由电刺激的人为性质导致的可能性，在未麻醉动物的清醒和慢波睡眠状态下，对新皮层、鼻周和内嗅自发放电进行了互相关分析。同样，在这两种状态下几乎都没有获得传播的证据。3）为测试仅在狭窄时间窗口内大量神经元被激活时才会发生传播这一观点，我们计算了围绕大幅度尖波的新皮层、鼻周和内嗅神经元放电的事件周围直方图。然而，这些同步的内嗅放电也未能穿过鼻周皮质进行传播。这些发现表明，鼻周皮质不仅仅是新皮层和海马体之间的中继站，而是一个其特性仍有待确定的闸门。
