Markus E J, Barnes C A, McNaughton B L, Gladden V L, Skaggs W E
ARL Division of Neural Systems, Memory and Aging, University of Arizona, Tucson 85724.
Hippocampus. 1994 Aug;4(4):410-21. doi: 10.1002/hipo.450040404.
The effects of darkness on quantitative spatial firing characteristics of 235 hippocampal CA1 "complex spike" (CS) cells were studied in young and old Fischer-344 rats during food-motivated performance of a randomized, forced-choice task on an eight-arm radial maze. The room lights were turned on or off on alternate blocks of all eight arms. In the dark, a lower proportion of CS cells had "place fields," and the fields were less specific and less reliable than in the light. A small number of cells had place fields unique to the dark condition. Like CS cells, Theta cells showed a reduction in spatially related firing in the dark. The specificity and reliability of the place fields under both light and dark conditions were similar for both age groups. Increasing the salience of the environment, by increasing the light level and the number of visual cues in the light condition, did not affect the specificity or reliability of the place fields. Even though all rats had substantial prior experience with the environment, and were placed on the maze center under normal illumination before the first dark trial, the correlation between the firing pattern in the light and dark increased after the rat first traversed the maze in the light. Thus, even after considerable experience with the environment over days, experiencing the illuminated environment from different locations on a given day was a significant factor affecting subsequent location and reliability of place fields in darkness. While the task was simple and errors rare, rats that made fewer errors (i.e., re-entries into the previously visited arm) also had more reliable place cells, but no such correlation was found with place cell specificity. Thus, the reliability of spatial firing in the hippocampus may be more important for spatial navigation than the size of the place fields per se. Alternatively, both spatial memory and place field reliability may be modulated by a common variable, such as attention.
在年轻和老年Fischer-344大鼠执行八臂放射状迷宫的随机强制选择食物驱动任务期间，研究了黑暗对235个海马CA1区“复合锋电位”（CS）细胞定量空间放电特性的影响。在所有八条臂的交替组块中，房间灯光打开或关闭。在黑暗中，具有“位置野”的CS细胞比例较低，并且这些位置野比在光照下更不特异且更不可靠。少数细胞具有黑暗条件下特有的位置野。与CS细胞一样，θ细胞在黑暗中与空间相关的放电也减少。两个年龄组在光照和黑暗条件下位置野的特异性和可靠性相似。通过提高光照条件下的光照水平和视觉线索数量来增加环境的显著性，并不影响位置野的特异性或可靠性。尽管所有大鼠对该环境都有丰富的先前经验，并且在第一次黑暗试验前在正常光照下被放置在迷宫中心，但大鼠首次在光照下穿越迷宫后，光照和黑暗中的放电模式之间的相关性增加。因此，即使在数天内对环境有了相当多的经验之后，在给定的一天中从不同位置体验光照环境也是影响随后黑暗中位置野的位置和可靠性的一个重要因素。虽然任务简单且错误很少，但错误较少（即重新进入先前访问过的臂）的大鼠也有更可靠的位置细胞，但未发现与位置细胞特异性有这种相关性。因此，海马体中空间放电的可靠性对于空间导航可能比位置野本身的大小更重要。或者，空间记忆和位置野可靠性可能都受一个共同变量（如注意力）的调节。
