Takehara-Nishiuchi Kaori, Maal-Bared Geith, Morrissey Mark D
Department of Psychology, University of Toronto Toronto, ON, Canada.
Front Behav Neurosci. 2012 Jan 5;5:90. doi: 10.3389/fnbeh.2011.00090. eCollection 2011.
Memories are thought to be encoded as a distributed representation in the neocortex. The medial prefrontal cortex (mPFC) has been shown to support the expression of memories that initially depend on the hippocampus (HPC), yet the mechanisms by which the HPC and mPFC access the distributed representations in the neocortex are unknown. By measuring phase synchronization of local field potential (LFP) oscillations, we found that learning initiated changes in neuronal communication of the HPC and mPFC with the lateral entorhinal cortex (LEC), an area that is connected with many other neocortical regions. LFPs were recorded simultaneously from the three brain regions while rats formed an association between an auditory stimulus (CS) and eyelid stimulation (US) in a trace eyeblink conditioning paradigm, as well as during retention 1 month following learning. Over the course of learning, theta oscillations in the LEC and mPFC became strongly synchronized following presentation of the CS on trials in which rats exhibited a conditioned response (CR), and this strengthened synchronization was also observed during remote retention. In contrast, CS-evoked theta synchronization between the LEC and HPC decreased with learning. Our results suggest that communication between the LEC and mPFC are strengthened with learning whereas the communication between the LEC and HPC are concomitantly weakened, suggesting that enhanced LEC-mPFC communication may be a neuronal correlate for theoretically proposed neocortical reorganization accompanying encoding and consolidation of a memory.
记忆被认为是以分布式表征的形式编码于新皮层中。内侧前额叶皮层（mPFC）已被证明支持最初依赖海马体（HPC）的记忆表达，然而HPC和mPFC访问新皮层中分布式表征的机制尚不清楚。通过测量局部场电位（LFP）振荡的相位同步性，我们发现学习引发了HPC和mPFC与外侧内嗅皮层（LEC）之间神经元通讯的变化，LEC是一个与许多其他新皮层区域相连的区域。在大鼠以痕迹性眨眼条件反射范式在听觉刺激（CS）和眼睑刺激（US）之间形成关联时，以及在学习后1个月的记忆保持期内，同时从这三个脑区记录LFP。在学习过程中，在大鼠表现出条件反应（CR）的试验中，呈现CS后，LEC和mPFC中的theta振荡变得强烈同步，并且在远期记忆保持期也观察到这种增强的同步性。相反，随着学习，LEC和HPC之间由CS诱发的theta同步性降低。我们的结果表明，随着学习，LEC和mPFC之间的通讯增强，而LEC和HPC之间的通讯则随之减弱，这表明增强的LEC-mPFC通讯可能是理论上提出的伴随记忆编码和巩固的新皮层重组的神经元相关物。
