Schöpke R, Wolfer D P, Lipp H P, Leisinger-Trigona M C
Institute of Anatomy, University of Zürich, Switzerland.
Hippocampus. 1991 Jul;1(3):315-28. doi: 10.1002/hipo.450010322.
The extent of the infrapyramidal mossy fiber projection in CA3 (IIP-MF) at the midseptotemporal level correlates negatively with two-way avoidance learning and positively with performance in the radial maze, both tasks known to be sensitive to hippocampal lesions. If hippocampal structural variations are causing behavioral variations, one must predict positive correlations between the extent of the IIP-MF and performance in swimming navigation. Thus, the authors studied learning and reversal learning of swimming navigation in mice in which the size of the IIP-MF had been randomized by means of systematic crosses and in 2 mouse strains known for differential infrapyramidal projections (C57BL/6 and DBA/2). In 19 random-bred mice (9 male, 10 female), the extent of the IIP-MF showed negative correlations with swimming time after platform reversal (day 4: r = -0.50, P < .03; day 5 r = -0.73, P < .001), but none during acquisition of the task. In addition, statistical analysis suggested an influence of asymmetrically distributed mossy fiber projections during reversal learning. The strain comparison between 18 DBA/2 and 16 C57BL/6 male mice confirmed these results: no strain difference during days 1-3, and a significantly faster swimming time in the strain C57BL/6 (with large IIP-MF) at day 5 (second day of reversal), associated with significantly more crossings of the former platform location during the early phases of reversal learning. This latter measure was also negatively correlated with asymmetry of the IIP-MF in both strains. Finally, variations of the IIP-MF were correlated partially with adjustment of swimming speed that appeared to depend on size and asymmetry of CA4 as well. Thus, natural variations in the size of the IIP-MF distribution, and, perhaps, of CA4, appear to linearly influence processes directly involved in complex spatial learning.
在中隔颞叶水平，CA3区（IIP-MF）的锥体下苔藓纤维投射范围与双向回避学习呈负相关，与放射状迷宫任务的表现呈正相关，这两项任务均对海马损伤敏感。如果海马结构变异导致行为变异，那么人们必然会预测IIP-MF范围与游泳导航表现之间存在正相关。因此，作者研究了通过系统杂交使IIP-MF大小随机化的小鼠以及已知锥体下投射不同的两种小鼠品系（C57BL/6和DBA/2）在游泳导航中的学习和逆向学习情况。在19只随机繁殖的小鼠（9只雄性，10只雌性）中，IIP-MF范围与平台反转后的游泳时间呈负相关（第4天：r = -0.50，P < 0.03；第5天：r = -0.73，P < 0.001），但在任务习得期间无相关性。此外，统计分析表明逆向学习过程中苔藓纤维投射不对称分布存在影响。对18只DBA/2雄性小鼠和16只C57BL/6雄性小鼠的品系比较证实了这些结果：第1 - 3天无品系差异，在第5天（反转的第二天），C57BL/6品系（IIP-MF大）的游泳时间显著更快，且在逆向学习早期阶段，该品系穿过先前平台位置的次数显著更多。后一项指标在两个品系中也与IIP-MF的不对称性呈负相关。最后，IIP-MF的变异部分与游泳速度的调整相关，而游泳速度的调整似乎也取决于CA4的大小和不对称性。因此，IIP-MF分布大小以及可能还有CA4大小的自然变异似乎对复杂空间学习直接涉及的过程产生线性影响。
