Morphological Features of Human Dendritic Spines

Morphological heterogeneity of neurons in the human central amygdaloid nucleus

“…The heterogeneity in the number of primary dendrites of human CeA neurons ranges through the features of unipolar to polygonal cells, for example. The dendritic structure also relates to the biophysical implications of dendritic length, diameter, and impedance for the modulation of postsynaptic potentials (Renner & Rasia‐Filho, 2023 and references therein). Whereas the use of acute slices from neurosurgical resection and recordings of dozens of cells (Planert et al., 2021) was not done for the human CeA, that would be an alternative way to obtain morphological and electrophysiological data for local cells and test differences in dendritic morphology and function.…”

“…That would be one reason why few spines are found in CeA neurons. Axons contacting smooth dendritic shafts might promote “direct” synaptic responses with more variability in the amplitude of excitatory postsynaptic potentials and less modulation than those axo‐spinous contacts, making an input/output ratio for fast firing patterns and output (Renner & Rasia‐Filho, 2023 and references therein). In addition, volume transmission by monoaminergic varicose axons would also maintain a tonic control of CeA function through receptors that do not form conventional synapses.…”

“…Those dendritic spines that occur in CeA neurons would enhance wiring and computational power, forming networks with increased flexibility and modulation of the synaptic strength along different dendritic distances, and branching orders. Spines also contain several molecular pathways that promote activity‐dependent integration and learning possibilities (Kasai, 2023; Rasia‐Filho et al., 2023a, 2023b; Renner & Rasia‐Filho, 2023). In line with the existence of neighbor axodendritic contacts, axo‐spiny contacts on shorter and wider spines (stubby or wide ones) may transfer charge into the parent dendrite with lower resistance (Coss & Perkel, 1985), involve a higher density of postsynaptic glutamate receptors than longer spines, and generate larger excitatory postsynaptic currents (Segal, 2010).…”

“…Human dendritic spines were classified as in previous reports (Dall'Oglio et al., 2015; Guerra et al., 2023; Renner & Rasia‐Filho, 2023 and references therein). The following morphological parameters were studied: (1) the presence, length, and diameter of the spine neck, (2) the number of spine heads emerging from a single spine neck, (3) the spine head diameter, and (4) the spine head shape.…”

“…They are multifunctional units serving as complex postsynaptic elements (Helm et al., 2021; Hruska et al., 2018) that greatly increase the neuronal computational possibilities involving synaptic dynamics and plasticity (Kasai, 2023; Rasia‐Filho et al., 2023a, 2023b). Human spines may differ in number, shape, and size depending on the dendritic location, as well as along main dendritic shafts or collaterals (detailed in Renner & Rasia‐Filho, 2023).…”