Young B J, Fox G D, Eichenbaum H
Department of Psychology, University of North Carolina, Chapel Hill 27599.
J Neurosci. 1994 Nov;14(11 Pt 1):6553-63. doi: 10.1523/JNEUROSCI.14-11-06553.1994.
The observation of hippocampal place cells forms a major line of evidence supporting the view that the hippocampus is dedicated to spatial processing. However, most studies demonstrating the spatial properties of hippocampal unit activity have employed tasks that emphasize spatial cues but minimize nonspatial cues. In the present experiment we recorded the activity of hippocampal complex-spike cells from rats performing a nonspatial radial maze task. Performance in this task was guided by local visual-tactile cues on the maze arms, while distal spatial cues were minimized and made irrelevant. The influence of three variables on unit activity was examined:type of cue on an arm, spatial location of an arm, and the relative position of the animal on an arm. Of the units recorded, almost one-fifth were classified as "cue cells" in that their activity was associated with cue type but not spatial location. Conversely, a similar proportion of the units were classified as "place cells" in that their activity was associated with location, but not cue type. In an additional similar proportion of units, firing was influenced only by relative position and not by local cues or spatial locations. For the majority of units, however, firing was related to combinations of these three variables, indicating that most hippocampal neurons encoded conjunctions or relations between spatial and local cue information. This pattern of results indicates that when local rather than distal spatial cues are emphasized, hippocampal neural activity is strongly influenced by salient nonspatial cues and shows no overwhelming predominance of place coding. These findings are at odds with the hypothesis that the hippocampus is selectively involved in spatial processing and, conversely, support the broader view that the hippocampus encodes both spatial and nonspatial relations among important experimental variables.
对海马体位置细胞的观察构成了支持海马体专门负责空间处理这一观点的主要证据链。然而，大多数证明海马体单元活动具有空间特性的研究采用的任务都强调空间线索而尽量减少非空间线索。在本实验中，我们记录了执行非空间放射状迷宫任务的大鼠海马体复合锋电位细胞的活动。该任务的表现由迷宫臂上的局部视觉 - 触觉线索引导，而远端空间线索被尽量减少并变得无关紧要。我们研究了三个变量对单元活动的影响：臂上线索的类型、臂的空间位置以及动物在臂上的相对位置。在所记录的单元中，近五分之一被归类为“线索细胞”，因为它们的活动与线索类型相关而与空间位置无关。相反，类似比例的单元被归类为“位置细胞”，因为它们的活动与位置相关而与线索类型无关。另有类似比例的单元，其放电仅受相对位置影响，而不受局部线索或空间位置影响。然而，对于大多数单元来说，放电与这三个变量的组合有关，这表明大多数海马神经元编码空间和局部线索信息之间的结合或关系。这种结果模式表明，当强调局部而非远端空间线索时，海马神经活动受到显著非空间线索的强烈影响，并且位置编码没有压倒性的优势。这些发现与海马体选择性参与空间处理的假设不一致，相反，支持了更广泛的观点，即海马体编码重要实验变量之间的空间和非空间关系。
