Zhu X O, Brown M W, Aggleton J P
Department of Anatomy, University of Bristol, UK.
Eur J Neurosci. 1995 Apr 1;7(4):753-65. doi: 10.1111/j.1460-9568.1995.tb00679.x.
This study was conducted to discover whether the rat cortex contains neurons that signal information concerning the previous occurrence of stimuli, as has been found in the primate. Recordings of the activity of 396 single neurons were made while unanaesthetized rats were shown objects. The effects on neuronal responsiveness of stimulus repetition and of the relative familiarity of the stimuli were sought. The areas sampled were the rhinal (entorhinal and perirhinal) cortex, area TE of the temporal cortex, the lateral occipital cortex and the hippocampal formation. The response to the first presentations of objects was significantly different from that to their second presentations for 63 (34%) of the 185 responsive neurons; for 39 of the neurons the response was smaller when the stimulus was repeated, whereas for 24 it was larger. The incidence of decremental responses was higher in the non-hippocampal cortex than in the hippocampal formation, while the incidence of incremental responses was higher in the hippocampal formation than other cortical areas. The response to unfamiliar objects was significantly different from that to highly familiar objects for 15 (22%) of 67 responsive neurons so tested; for 12 of the neurons the response was smaller when the stimulus was repeated, and for three it was larger; most of these neurons were found in area TE. The responses of ten familiarity neurons varied significantly with the relative familiarity of the stimuli but not with stimulus repetition; the responses of seven recency neurons varied significantly upon stimulus repetition but not with the relative familiarity of the stimuli. Thus information concerning stimulus repetition and familiarity is separably encoded at the single neuron level in the rat cortex. The results demonstrate that in the rat cortex as in the monkey cortex there are neurons that signal information concerning the prior occurrence of stimuli; such information is of importance to recognition memory, working memory and priming memory.
本研究旨在探究大鼠皮层是否含有能像在灵长类动物中那样发出有关先前刺激出现信息信号的神经元。在未麻醉的大鼠观看物体时，对396个单神经元的活动进行了记录。研究了刺激重复以及刺激的相对熟悉程度对神经元反应性的影响。采样区域包括嗅周皮层（内嗅皮层和嗅周皮层）、颞叶皮层的TE区、枕外侧皮层和海马结构。对于所测试的185个反应性神经元中的63个（34%），对物体首次呈现的反应与对其第二次呈现的反应显著不同；对于其中39个神经元，刺激重复时反应变小，而对于24个神经元，反应变大。非海马皮层中递减反应的发生率高于海马结构，而海马结构中递增反应的发生率高于其他皮层区域。对于所测试的67个反应性神经元中的15个（22%），对不熟悉物体的反应与对非常熟悉物体的反应显著不同；对于其中12个神经元，刺激重复时反应变小，对于3个神经元反应变大；这些神经元大多位于TE区。10个熟悉度神经元的反应随刺激的相对熟悉程度显著变化，但不随刺激重复而变化；7个新近度神经元的反应在刺激重复时显著变化，但不随刺激的相对熟悉程度而变化。因此，关于刺激重复和熟悉程度的信息在大鼠皮层的单神经元水平上是分开编码的。结果表明，在大鼠皮层中，如同在猴皮层中一样，存在能发出有关先前刺激出现信息信号的神经元；此类信息对识别记忆、工作记忆和启动记忆很重要。
