Target‐specific differences in somatodendritic morphology of layer V pyramidal neurons in rat motor cortex

Abstract

Dendritic geometry has been shown to be a critical determinant of information processing and neuronal computation. However, it is not known whether cortical projection neurons that target different subcortical nuclei have distinct dendritic morphologies. In this study, fast blue retrograde tracing in combination with intracellular Lucifer yellow injection and diaminobenzidine (DAB) photoconversion in fixed slices was used to study the morphological features of corticospinal, corticostriatal, and corticothalamic neurons in layer V of rat motor cortex. Marked differences in the distribution of soma, somal size, and dendritic profiles were found among the three groups of pyramidal neurons. Corticospinal neurons were large, were located in deep layer V, and had the most expansive dendritic fields. The apical dendrites of corticospinal pyramidal neurons were thick, spiny, and branched. In contrast, nearly all corticostriatal neurons were small cells located in superficial layer V. Their apical dendritic shafts were significantly more slender, though spiny like those of corticospinal neurons. Corticothalamic neurons, which were located in superficial layer V and in layer VI, had small or medium-sized soma, slender apical dendritic shafts, and dendrites that were largely spine free. This study indicates that, in layer V of rat motor cortex, each population of projection neurons has a unique somatodendritic morphology and suggests that distinct modes of cortical information processing are operative in corticospinal, corticostriatal, and corticothalamic neurons.

Recurrent Connection Patterns of Corticostriatal Pyramidal Cells in Frontal Cortex

“…In this study, we confirmed that CCS and CPn cells are mutually exclusive groups using doublefluorescence markers. Apical dendritic tufts are different in size among pyramidal cell subtypes (Hallman et al, 1988;Hübener et al, 1990;Kasper et al, 1994;Gao and Zheng, 2004). In addition to their striking differences in axonal projection, we found significant morphological differences in their apical tuft structures (Fig.…”

“…In the neocortex, pyramidal cells projecting to the same target areas are aggregated within given cortical layers, with each layer containing several projection types (Jones, 1984;Kasper et al, 1994;Gao and Zheng, 2004). Even within microregions of the same cortical layer, there can exist several projection cell types (Lévesque et al, 1996b;Vercelli et al, 2004;Gabbott et al, 2005).…”

Specialized Cortical Subnetworks Differentially Connect Frontal Cortex to Parahippocampal Areas

“…1 B, E, 2A), and CTh cells were localized in both L5a and L6 (Figs. 1 D, 2A) (Deschênes et al, 1994;Gao and Zheng, 2004). Dual retrograde labeling revealed that L5 PRCprojecting cells were overlapped with the upper CCS group (Fig.…”

Rehabilitation drives enhancement of neuronal structure in functionally relevant neuronal subsets

“…Intracellular injection of neurons in lightly fixed slices was performed as previously described with modifications (37,38). All animals underwent intracellular injections of LY.…”