Stewart M, Fox S E
Department of Physiology, SUNY Health Science Center, Brooklyn 11203.
Exp Brain Res. 1989;77(3):507-16. doi: 10.1007/BF00249604.
On the basis of spontaneous firing patterns and relations to the hippocampal theta rhythm, three cell types were identified within the medial septal nucleus and vertical limb of the nucleus of the diagonal band of Broca (MSN-NDB). In addition to the well known rhythmically bursting cells that fired in bursts on each cycle of the hippocampal theta rhythm, two other cell types are distinguished. "Clock" cells fired at high rates with a very regular, periodic firing pattern that was unrelated to the theta rhythm. "Irregular" cells fired at much lower rates, especially during theta rhythm, and had a pseudo-random firing pattern. The firing of "irregular" cells was often significantly phase-locked to the hippocampal theta rhythm. Crude estimates of the relative proportions of these cell types suggest that the rhythmically bursting cells comprise about 75% of the cells of the MSN-NDB. These three cell types bear a remarkable resemblance, in firing patterns and relative proportions, to the three principal cell types of the medial septal nuclei described in the freely moving rat (Ranck 1976). Measurements of the preferred phases of firing of 128 rhythmically bursting septal neurons (including 22 atropine-resistant and 11 atropine-sensitive cells) indicate that there is no single preferred phase of firing for the population. Rather the distribution of phases over the theta cycle is statistically flat. Variations in recording locations cannot account for this distribution since large differences in preferred phase were found for pairs of cells at the same location. Similarly, plotting only the group of cells identified as projection cells by antidromic activation from the fimbria/fornix, failed to reveal a peak in the distribution. In contrast to the rhythmically bursting cells, the distribution of preferred firing phases for the "irregular" cells with a significant phase-locking to the theta rhythm did have a clear peak. The peak occurred near the dentate theta rhythm positivity, consistent with the hypothesis that they are driven by feedback from CA1 complex-spike cells.
根据自发放电模式以及与海马θ节律的关系，在内侧隔核和布罗卡斜角带核垂直支（MSN-NDB）中识别出三种细胞类型。除了众所周知的在海马θ节律的每个周期以爆发形式放电的节律性爆发细胞外，还区分出另外两种细胞类型。“时钟”细胞以非常规则的周期性放电模式高速放电，该模式与θ节律无关。“不规则”细胞放电频率低得多，尤其是在θ节律期间，并且具有伪随机放电模式。“不规则”细胞的放电通常与海马θ节律显著锁相。对这些细胞类型相对比例的粗略估计表明，节律性爆发细胞约占MSN-NDB细胞的75%。这三种细胞类型在放电模式和相对比例上与自由活动大鼠中描述的内侧隔核的三种主要细胞类型非常相似（兰克，1976年）。对128个节律性爆发的隔区神经元（包括22个抗阿托品和11个对阿托品敏感的细胞）放电的最佳相位测量表明，该群体没有单一的最佳放电相位。相反，θ周期内相位的分布在统计学上是平坦的。记录位置的差异无法解释这种分布，因为在同一位置的细胞对中发现了最佳相位的巨大差异。同样，仅绘制通过来自穹窿/穹窿下回的逆向激活确定为投射细胞的细胞组，也未能揭示分布中的峰值。与节律性爆发细胞相反，与θ节律有显著锁相的“不规则”细胞的最佳放电相位分布确实有一个明显的峰值。该峰值出现在齿状θ节律阳性附近，这与它们由CA1复合峰细胞的反馈驱动的假设一致。
