Weible A P, O'Reilly J-A, Weiss C, Disterhoft J F
Department of Physiology, Northwestern University Institute for Neuroscience, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, IL 60611, USA.
Neuroscience. 2006 Sep 1;141(3):1123-37. doi: 10.1016/j.neuroscience.2006.04.065. Epub 2006 Jun 6.
Previous studies demonstrating a critical role of the hippocampus during trace eye-blink conditioning have focused primarily upon the dorsal portion of the structure. However, evidence suggests that a functional differentiation exists along the septotemporal axis of the hippocampus. In the present study, the activity of 2588 single cornu ammonis region 1 pyramidal neurons of the dorsal hippocampus and ventral hippocampus were recorded during trace and pseudo-eye-blink conditioning of the rabbit. Learning-related increases in dorsal hippocampus neuron firing rates were observed immediately prior to behavioral criterion, and increased over the course of training. Activation of dorsal hippocampus neurons during trace conditioning was also greater than that of ventral hippocampus neurons, including during the trace interval, in well-trained animals. An unexpected difference in the patterns of learning-related activity between hemispheres was also observed. Neurons of the dorsal hippocampus ipsilateral and contralateral to the trained eye, exhibiting significant increases in firing rate [rate increasing neurons], demonstrated the greatest magnitude of activation early and late in training, respectively. Rate increasing neurons of the dorsal hippocampus also exhibited a greater diversity of response profiles, with 69% of dorsal hippocampus rate increasing neurons exhibiting significant increases in firing rate during the conditioned stimulus and/or trace intervals, compared with only 8% of ventral hippocampus rate increasing neurons (the remainder of which were significantly responsive during only the unconditioned stimulus and/or post-unconditioned stimulus intervals). Only modest learning-related activation of ventral hippocampus neurons was observed, reflected as an increase in conditioning stimulus-elicited rate increasing neuron response magnitudes over the course of training. No differences in firing rate between dorsal hippocampus and ventral hippocampus neurons during a 1-day pre-training habituation session were observed. Thus, dorsal hippocampus activation is more robust, suggesting a more substantial role for these neurons in the processing of temporal information during trace eye-blink conditioning.
先前的研究表明，海马体在痕迹性眨眼条件反射过程中起关键作用，这些研究主要聚焦于该结构的背侧部分。然而，有证据表明，海马体沿隔颞轴存在功能分化。在本研究中，在兔子的痕迹性和假性眨眼条件反射过程中，记录了2588个背侧海马体和腹侧海马体单个海马角1区锥体神经元的活动。在行为标准达成之前，立即观察到背侧海马体神经元放电率与学习相关的增加，且在训练过程中有所上升。在训练有素的动物中，痕迹性条件反射期间背侧海马体神经元的激活也大于腹侧海马体神经元，包括在痕迹间隔期间。还观察到半球之间与学习相关的活动模式存在意外差异。与训练眼同侧和对侧的背侧海马体神经元，放电率显著增加（即放电率增加神经元），分别在训练早期和晚期表现出最大程度的激活。背侧海马体的放电率增加神经元也表现出更广泛的反应谱，69%的背侧海马体放电率增加神经元在条件刺激和/或痕迹间隔期间放电率显著增加，相比之下，腹侧海马体放电率增加神经元只有8%（其余的仅在非条件刺激和/或非条件刺激后间隔期间有显著反应）。仅观察到腹侧海马体神经元有适度的与学习相关的激活，表现为在训练过程中条件刺激诱发的放电率增加神经元反应幅度有所增加。在为期1天的训练前习惯化阶段，未观察到背侧海马体和腹侧海马体神经元放电率的差异。因此，背侧海马体的激活更强，表明这些神经元在痕迹性眨眼条件反射期间处理时间信息方面发挥更重要的作用。
