Figure 1.

Three firing subtypes of L5 pyramidal cells and their correlation with projection targets. A, Dendritic reconstructions and voltage responses to current injections in SA, SA-d, and FA type L5 pyramidal cells (pulse duration, 1 s; amplitude, from −400 to +500 pA in 100pA steps). Asterisk indicates initial doublet spikes. Inset in SA-d, initial doublet (*) at an expanded time scale and reduced voltage scale. B, Distribution of the relation between maximum spike frequency and the adaptation index (f7/f2) obtained from spike trains generated by current injection (500pA) in three L5 pyramidal subtypes (n = 183, 161, and 180, for SA, SA-d, and FA type cell, respectively). Spike frequency (f) was calculated from each interspike interval (see inset in C). Note that three clusters are readily identified by the two firing parameters. C, Comparisons of f1/f2 (burst index) and f7/f2 (adaptation index) between SA, SA-d, and FA type pyramidal subtypes (n = 150, respectively). Data are means ± SD; **p < 0.01. D, Proportion of firing subtypes among CPn (n = 39), COM (n = 38) and CCS (n = 39) cells identified by retrograde fluorescent tracers.