Spindle-Shaped Neurons in the Human Posteromedial (Precuneus) Cortex

Abstract

The human posteromedial cortex (PMC), which includes the precuneus (PC), represents a multimodal brain area implicated in emotion, conscious awareness, spatial cognition, and social behavior. Here, we describe the presence of Nissl-stained elongated spindle-shaped neurons (suggestive of von Economo neurons, VENs) in the cortical layer V of the anterior and central PC of adult humans. The adapted “single-section” Golgi method for postmortem tissue was used to study these neurons close to pyramidal ones in layer V until merging with layer VI polymorphic cells. From three-dimensional (3D) reconstructed images, we describe the cell body, two main longitudinally oriented ascending and descending dendrites as well as the occurrence of spines from proximal to distal segments. The primary dendritic shafts give rise to thin collateral branches with a radial orientation, and pleomorphic spines were observed with a sparse to moderate density along the dendritic length. Other spindle-shaped cells were observed with straight dendritic shafts and rare branches or with an axon emerging from the soma. We discuss the morphology of these cells and those considered VENs in cortical areas forming integrated brain networks for higher-order activities. The presence of spindle-shaped neurons and the current discussion on the morphology of putative VENs address the need for an in-depth neurochemical and transcriptomic characterization of the PC cytoarchitecture. These findings would include these spindle-shaped cells in the synaptic and information processing by the default mode network and for general intelligence in healthy individuals and in neuropsychiatric disorders involving the PC in the context of the PMC functioning.

Human cortical amygdala dendrites and spines morphology under open‐source three‐dimensional reconstruction procedures

“…We followed the procedures reported in Vásquez et al (2018). First, we used microscopic images obtained using the "single-section" Golgi method adapted for the human brain (Dall'Oglio et al, 2010, 2013Fuentealba-Villarroel et al, 2022;Rasia-Filho et al, 2021). Then, we proceeded to obtain (1) 3D reconstructed images of the neuronal cell body and the dendritic ramification using a neuronal tracing procedure, and (2) 3D reconstructions of heterogeneous dendritic spines using a…”

Unraveling Brain Microcircuits, Dendritic Spines, and Synaptic Processing Using Multiple Complementary Approaches

“…Spines are morphologically diverse, ranging in a continuum of number, shape, and size classified according to their head and neck features ( Figure 1C ). These include: stubby/wide, thin, mushroom, ramified, “atypical” or multiform spines, including “intermediate” shapes, “double” spines, and thorny excrescences, among others (Fiala and Harris, 1999 ; Arellano et al, 2007 ; Bourne and Harris, 2007 , 2009 ; Stewart et al, 2014 ; Fuentealba-Villarroel et al, 2021 ; see also Ruszczycki et al, 2012 ; Pchitskaya and Bezprozvanny, 2020 ). Spine shape involves local actin organization, second messengers, and organelles (e.g., endoplasmic reticulum and ribosomes, Yuste, 2010 ; Sala and Segal, 2014 ; Miermans et al, 2017 ; Okabe, 2020 ; for mitochondria see Li et al, 2004 ).…”

“…Human spines, also, show a high diversity of size and shapes (Dall'Oglio et al, 2015 ; Vásquez et al, 2018 ; Rasia-Filho et al, 2021 ). The functional implication of long “silent” spines (Yuste, 2013 ) and those of convoluted shapes, observed from subcortical to cortical human neurons (Dall'Oglio et al, 2015 ; Fuentealba-Villarroel et al, 2021 ), need additional studies. Multiform spines likely indicate the existence of multisynaptic sites for signaling compartmentalization and further computational possibilities within functional microdomains (Chen and Sabatini, 2012 ; Dall'Oglio et al, 2015 ; Reberger et al, 2018 ).…”

Transcriptome Profiling of the Dorsomedial Prefrontal Cortex in Suicide Victims

“…The precuneus plays a significant role in the human brain's mental imagination, individualization of cognitive processes, as reflections of signals from the external world, introspection, self-awareness, creativity and intelligence [19][20][21][22][23]. The precuneus directly projects to the supplementary and the presupplementary motor cortices [24,25]. In addition, the precuneus also participates in the control of the motor executive program through connections with the DMPFC [26].…”