Yoganarasimha D, Yu Xintian, Knierim James J
Department of Neurobiology and Anatomy, W. M. Keck Center for the Neurobiology of Learning and Memory, The University of Texas Medical School, Houston, Texas 77225, USA.
J Neurosci. 2006 Jan 11;26(2):622-31. doi: 10.1523/JNEUROSCI.3885-05.2006.
Place cells of the hippocampal formation encode a spatial representation of the environment, and the orientation of this representation is apparently governed by the head direction cell system. The representation of a well explored environment by CA1 place cells can be split when there is conflicting information from salient proximal and distal cues, because some place fields rotate to follow the distal cues, whereas others rotate to follow the proximal cues (Knierim, 2002a). In contrast, the CA3 representation is more coherent than CA1, because the place fields in CA3 tend to rotate in the same direction (Lee et al., 2004). The present study tests whether the head direction cell network produces a split representation or remains coherent under these conditions by simultaneously recording both CA1 place cells and head direction cells from the thalamus. In agreement with previous studies, split representations of the environment were observed in ensembles of CA1 place cells in approximately 75% of the mismatch sessions, in which some fields followed the counterclockwise rotation of proximal cues and other fields followed the clockwise rotation of distal cues. However, of 225 recording sessions, there was not a single instance of the head direction cell ensembles revealing a split representation of head direction. Instead, in most of the mismatch sessions, the head direction cell tuning curves rotated as an ensemble clockwise (94%) and in a few sessions rotated counterclockwise (6%). The findings support the notion that the head direction cells may be part of an attractor network bound more strongly to distal landmarks than proximal landmarks, even under conditions in which the CA1 place representation loses its coherence.
海马结构中的位置细胞编码环境的空间表征，而这种表征的方向显然受头部方向细胞系统的支配。当来自显著近端和远端线索的信息相互冲突时，CA1位置细胞对充分探索过的环境的表征可能会分裂，因为一些位置野会旋转以跟随远端线索，而另一些则会旋转以跟随近端线索（克涅里姆，2002a）。相比之下，CA3的表征比CA1更连贯，因为CA3中的位置野倾向于朝同一方向旋转（李等人，2004）。本研究通过同时记录来自丘脑的CA1位置细胞和头部方向细胞，测试在这些条件下头部方向细胞网络是产生分裂表征还是保持连贯。与先前的研究一致，在大约75%的不匹配实验中，在CA1位置细胞集合中观察到环境的分裂表征，其中一些位置野跟随近端线索的逆时针旋转，而其他位置野跟随远端线索的顺时针旋转。然而，在225次记录实验中，没有一个头部方向细胞集合出现头部方向的分裂表征。相反，在大多数不匹配实验中，头部方向细胞的调谐曲线作为一个整体顺时针旋转（94%），在少数实验中逆时针旋转（6%）。这些发现支持了这样一种观点，即即使在CA1位置表征失去连贯性的情况下，头部方向细胞可能是吸引子网络的一部分，与远端地标相比，它们与近端地标联系更紧密。
