Class I and class II ganglion cells of rabbit retina: Quantitative analysis of dendritic branching patterns

Class I and class II ganglion cells, distinguished from one another in a companion paper, were analyzed in regard to their dendritic branching patterns by determination of: 1) mean “branching density” (BD), 2) “radial branching frequency” (RBF), and 3) “branch length distributions” (BLDs; Famiglietti [ 1992a] J Comp Neurol 324:295–321). Branching density of class II cells exceeded that of class I cells by a factor of two, when compared at the same retinal location, but declined with increasing distance from the visual streak ( dvs ). A one‐bin difference in RBF between class I and class II cells was not statistically significant. BLDs are scatter‐plots of individual preterminal and terminal branch lengths versus the distances of their origins from the soma. The parameters m p and m t , the slopes of regression lines fitted to the preterminal and terminal BLDs, respectively, were determined; m p , but not m t , was relatively independent of dvs , and was used empirically to determine a boundary value, m p = +5.0, separating “radiate” from “tufted” dendritic branching. Similarity of class I (m p = +8.6 ± 4.6) and class II (m p = +1.4 ± 5.2) cells did not allow a statistically significant separation of the two classes, based upon branching pattern alone; however, m p together with m t easily separated class I cells (m t = −17.8 ± 10.0) and particularly “tufted” class II cells (m t = −16 ± 9.3) from “tufted” class III.1 ganglion cells (Famiglietti, 1992a), with their qualitatively different, more regular branching (m p = +2.1 ± 0.85; m t = +0.65 ±4.9). J. Comp. Neurol. 478:347–358, 2004. © 2004 Wiley‐Liss, Inc.