Neurons
Nassir H. Sabah in Neuromuscular Fundamentals, 2020
Neurons also differ greatly in the shapes and sizes of their cell bodies and in the extent of their dendritic and axonal arborizations. Neuronal cell bodies may be round, oblong, fusiform, or pyramidal in shape. The structure of pyramidal cells (Figure 7.1c), found in the cerebral cortex, hippocampus, and amygdala, differs somewhat between different regions but is characterized by two sets of dendrites: Basal dendrites that arise from the base of the pyramidal cell body and then branch more extensively, andA single thick apical dendrite of a few microns diameter that stems from the apex of the pyramid and branches with distance away from the cell body and terminates in what is referred to as a distal tuft or tuft dendrites. Some dendrites branch from the trunk of the apical dendrite and are referred to as oblique dendrites.
Facilitating the Integration of Modern Neuroscience into Noninvasive BCIs
Chang S. Nam, Anton Nijholt, Fabien Lotte in Brain–Computer Interfaces Handbook, 2018
EEG largely reflects the summed activity from large populations of pyramidal neurons (Hämäläinen et al. 1993), which are the largest and most common excitatory neurons in the cortex. Pyramidal neurons are generally oriented with the “trunk” of their large dendritic tree (called the apical dendrite) oriented normal to the cortical surface. Therefore, when pyramidal neurons are influenced by excitatory or inhibitory postsynaptic potentials (PSPs), charged ions flow within the neuron primarily along an axis aligned with the apical dendrite. This charge flow is often referred to as the “primary current.” Since charge cannot accumulate in the brain, “secondary” (or volume) current loops also flow extracellularly throughout the head to compensate for the primary current (Lopes da Silva & Van Rotterdam 2011). Therefore, an activation pattern resembling a source-sink configuration arises that mimics the characteristics of a current dipole—a fact that simplifies source imaging (Dale & Sereno 1993; Hämäläinen et al. 1993; Lopes da Silva & Van Rotterdam 2011) as discussed later. These PSP activations (lasting tens to hundreds of milliseconds) are much slower than action potentials (lasting ~1 ms), so the PSP activations of a population of neurons are more likely to temporally overlap (Lopes da Silva 2010). Combined with the aligned arrangement of these neurons, the field potentials of simultaneously active neurons add constructively in space and time to become detectible outside the head (Lopes da Silva & Van Rotterdam 2011).
The effect of experimentally-induced diabetes on rat hippocampus and the potential neuroprotective effect of Cerebrolysin combined with insulin. A histological and immunohistochemical study
Published in Egyptian Journal of Basic and Applied Sciences, 2023
Doaa El-Adli, Salwa A. Gawish, Amany AbdElFattah Mohamed AbdElFattah, Mona Fm. Soliman
The hippocampal formation consisted of hippocampus proprius, dentate gyrus (DG) and the subicular cortex (SC). The hippocampus proprius could be differentiated into CA1, CA2, CA3 and CA4 regions. The DG had a crest and upper and lower blades surrounding CA4 (Figure 1 (a and b)). The hippocampus proprius was formed of the following layers; the alveus, stratum oriens (st.or), stratum pyramidale (st.py), stratum radiatum (st.rd) and stratum lacunosum-moleculare (st.lm). The alveus was the innermost layer containing nerve fibers and neuroglial cells. St.or showed scattered cells within the nerve fibers. St.py consisted of 5–6 layers of pyramidal cells. St.rd showed a radial streaking pattern of fibers. Finally, St.lm showed horizontal fibers, neuroglial cells and blood vessels (Figure 1 (c)). Pyramidal cells of CA3 appeared as large sized, loosely packed triangular cells with vesicular nuclei and prominent nucleoli. Each cell showed an apical dendrite ramifying toward St.rd and basal dendrites (Figure 1 (d)). The DG consisted of molecular, granular and polymorphic layers. The polymorphic layer showed scattered polymorphic nuclei. The granule cell layer (GCL) contained 8–9 compactly arranged layers of granule cells with vesicular nuclei and prominent nucleoli. Spindle-shaped immature cells with oval darkly stained nuclei were seen in the subgranular zone (SGZ) (Figure 1 (e and f)).
Better understanding the neurobiology of primary lateral sclerosis
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2020
P. Hande Ozdinler, Mukesh Gautam, Oge Gozutok, Csaba Konrad, Giovanni Manfredi, Estela Area Gomez, Hiroshi Mitsumoto, Marcella L. Erb, Zheng Tian, Georg Haase
The third important characteristic of UMNs is their long apical dendrite that extends toward the top layers of the cortex (Figure 1(B–C)). The apical dendrite is exceptionally important for their neuronal modulation, as this is the site for many different neuron populations to make a synaptic connection with the UMNs (28). The apical dendrite is extensively branched and the branches are adorned with hundreds of thousands, of spines (Figure 1(C)). These spines receive excitatory input from many different neuron types, such as callosal projection neurons, thalamacortical neurons and local circuitry neurons (Figure 1(B)) and (29). Thus, the health and stability of spines are important for these excitatory neurons to convey their information. Especially at the site of layer 2/3, CSMN receive most of their excitatory input, and this is one of their unique characteristics (30,31). The connectivity patterns of both long-distance projection neurons and local circuitry neurons are investigated by novel approaches, revealing the complex connectivity dynamics in the motor cortex and other regions (32,33).
Chronic altered light–dark cycle differentially affects hippocampal CA1 and DG neuronal arborization in diurnal and nocturnal rodents
Published in Chronobiology International, 2022
Vivek Verma, Ruchika Kumari, Muniyandi Singaravel
Dendritic morphology of hippocampus CA1 pyramidal neurons displays dendritic branching along with spines. Chronic constant dark and chronic constant light exposure for four weeks showed significant change in the complexity of pyramidal neurons in squirrels and mice. Representative Golgi-Cox-stained images of CA1 pyramidal neurons are shown in squirrels (Figure 2a) and mice (Figure 2b) in all the three groups LD (control), DD and LL. First, the total dendritic length and basal dendritic length of CA1 pyramidal neurons in both squirrels and mice were measured using Image J. In squirrels, the total and basal dendritic lengths were significantly reduced in DD and LL groups as compared to LD (p < .001) (Figure 2 c,e). The total and basal dendrites were further reduced significantly in LL exposed squirrels compared to the DD group (p < .01 and p < .001, respectively) (Figure 2c, e). Furthermore, in mice, total dendritic length was significantly increased in the DD group and significantly reduced in the LL group than LD (p < .001 for both) (Figure 2d). Additionally, a statistically significant decrease in total dendritic length was observed in LL than DD group in mice (p < .001) (Figure 2d). Similarly, the basal dendritic length in mice showed a significant increase in DD and a significant decrease in the LL group than LD control (p < .001 and p < .01, respectively) (Figure 2f). A significant decrease in basal dendritic length was also found in LL exposed mice than DD (p < .001) (Figure 2f). Second, the number of basal dendrites of pyramidal neurons in both the rodents was counted using Image J. In squirrels, it showed a significant reduction in DD and LL than LD group (P < .001 for both) and a statistically non-significant but reducing trend was observed in LL than DD group (Figure 2g). Moreover, a significant increase in basal dendrite number was observed in DD group mice than LD group (p < .01); however, an insignificant reduction in basal dendrite number in LL exposed mice was observed as compared to LD (Figure 2h). A significant reduction in basal dendrite number was also reported in mice exposed to LL than DD (p < .001) (Figure 2h). Third, the diameter of apical dendrites was measured precisely at the region where the apical dendrite arose from the soma. The results in squirrels showed a significant decrease in the diameter of apical dendrite of CA1 pyramidal neurons in both the DD and LL group as compared with the control group (p < .001 for both) (Figure 2i). In addition to this, the diameter of apical dendrite was also significantly reduced in LL squirrels than DD (p < .01) (Figure 2i). However, in mice, the diameter of apical dendrite was significantly increased in DD and significantly decreased in the LL group as compared to LD (p < .001 for both) (Figure 2j) .
Related Knowledge Centers
- Dendrite
- Entorhinal Cortex
- Excitatory Postsynaptic Potential
- Memory
- Olfactory System
- Pyramidal Cell
- Stellate Cell
- Prefrontal Cortex
- Hippocampus
- Learning