Normal Sleep
Ravi Gupta, S. R. Pandi Perumal, Ahmed S. BaHammam in Clinical Atlas of Polysomnography, 2018
EEG depicts the difference in the summative electrical potentials of the neuronal cells present in the cortex of the brain that lies beneath the electrodes. The cortex is made up of various types of neurons that include pyramidal cells and interneurons, besides glial cells. Pyramidal cells are excitatory in nature and they remain in contact with other cortical neurons through the fibers that they send to other cortical areas (known as association fibers). They also send fibers to the subcortical nuclei and spinal cord (known as projection fibers). These connections are usually reciprocal and thus, other cortical, subcortical nuclei and information coming from the peripheral nervous system (through spinal cord) regulate their activity in a complex manner. In addition, cortical interneurons that are primarily inhibitory in nature also regulate their activity.
Comparative Studies of Pyramidal Neurons in Visual Cortex of Monkeys
Jon H. Kaas, Christine E. Collins in The Primate Visual System, 2003
Cortex is composed of two basic types of neurons, spiny and nonspiny. Spiny cells that contain the neurotransmitter glutamate are widely believed to be excitatory (see References 21 through 24 for reviews). Pyramidal cells are the most common type of spiny neuron, comprising approximately 70% of all neurons in cortex.25 Arguably, pyramidal cells are the principal neurons of the cerebral cortex, generating nearly all cortically initiated excitation. They include many phenotypes, but are distinguished by their prominent apical dendrite and basal dendritic arbor (Figure 15.2). Nonspiny neurons include many different morphological types, most of which contain GABA (see References 24, 26, and 27 for reviews). They are characterized by different receptor profiles and project to different postsynaptic targets.28 In general, these cells are thought to be important in modulating the activity of excitatory neurons (see References 29 and 30 for reviews).
Changing the Paradigm from Neurochemical to Neuroelectrical Models
Hanno W. Kirk in Restoring the Brain, 2020
The mathematical formalism for the understanding of networks did not become available until the 1990s. The brain is perhaps the most elaborate exemplar in the known universe of what is known as the “small-world” model of networks. This is a combination of high local connectivity – composed of the dendritic tree on the input site and the axonal branching network on the output side – and of high distal connectivity. The latter follows from the fact that every cortical pyramidal cell participates in the communication with distal networks by means of axons that jointly constitute the cortical white matter. By virtue of the globally connected network of pyramidal cells, the brain is drawn into a unitary functional entity, with every part communicating with every other part more or less directly. As the National Institute of Health (NIH)-sponsored Human Connectome Project has shown, our brain is so interconnected that any synapse in the cortex is no more than three synapses away from any other synapse in the cortex.28
Modulation of brain insulin signaling in Alzheimer’s disease: New insight on the protective role of green coffee bean extract
Published in Nutritional Neuroscience, 2020
Hoda E. Mohamed, Mervat E. Asker, Nahla N. Younis, Mohamed A. Shaheen, Rana G. Eissa
The histopathological features of H and E stained hippocampus from all groups were illustrated in Fig. 5. The neurons of CA1 of the hippocampus of the NC group are composed of three layers; molecular, pyramidal, and polymorphic layers. The pyramidal cells had tightly packed pyramidal neurons with large rounded vesicular nuclei and long parallel cytoplasmic processes directed toward the molecular layer. The neuropil is composed of mostly of unmyelinated axons, dendrites, and glial cell. The nuclei of the neuroglia and blood vessels were observed. In FR-AD group, the nerve cells of the CA1 region of the hippocampus showed deeply stained acidophilic cytoplasm of some pyramidal cells (P). The nuclei are rather ill defined or fragmented, with a significant decline in the number of pyramidal cells. Some Pyramidal neurons with vesicular nuclei were also noticed. Congested blood vessels were also observed. Many dark cells were also seen around nerve cells.
Cortical projection neurons as a therapeutic target in multiple sclerosis
Published in Expert Opinion on Therapeutic Targets, 2020
Tatjana Beutel, Julia Dzimiera, Hannah Kapell, Maren Engelhardt, Achim Gass, Lucas Schirmer
Arguably, callosal long-range connections might be more vulnerable during serial WM tract damage as seen in MS patients, eventually leading to retrograde pathology and neuronal demise. Regarding cytoarchitectonic features, layers II/III typically consist of small- to medium-size pyramidal cells in high density [17]. With increased depth from the pial surface, these neurons show greater dendritic length and soma radius [29]. Based on their morphological features, they can be divided into two groups: so-called ‘slim-tufted’ neurons with a low density of branches and ‘profuse-tufted’ cells with a higher branch density [29]. Compared to rodents, pyramidal cells in the human cortical layer II/III form approximately twice as many synapses [30,31] suggesting a multifold increase in transmission and integration of information. Evolutionary, supragranular layer neurons developed more recently as compared to layer V/VI extra-cortical projection neurons. In relation to rodents, the layer II/III in human and other primates is greatly expanded suggesting the occurrence of a substantially increased intracortical connectivity in these species, which may have contributed significantly to the more advanced cortical function, however, may also make them more vulnerable for particular neurological diseases [24].
Attentional capture by physically salient stimuli in the gamma frequency is associated with schizophrenia symptoms
Published in The World Journal of Biological Psychiatry, 2018
Laura Kornmayer, Gregor Leicht, Christoph Mulert
On the cellular level, gamma oscillations are suggested to be induced by interaction of excitatory pyramidal cells with fast-spiking interneurons (Bartos et al. 2007; Cardin et al. 2009; Sohal et al. 2009). Thereby, excitatory pyramidal cell activation selectively gets synchronised ensuing gamma activity (Fries et al. 2001; Hasenstaub et al. 2005). Stimulus-evoked gamma activity at sensory visual sites close to the surface of the cortex is assumed to represent a transfer signal caused by the match of sensory input with higher cognitive representation. This was suggested by Herrmann et al. (2005) for the early evoked visual gamma-band response (GBR) occurring about 100 ms post-stimulus above occipital sites. The GBR over occipital areas was shown to be dependent on physical features of external stimuli and the execution of executive attention (Busch et al. 2004, 2006). Herrmann and Mecklinger (2001) assessed the visual evoked GBR for the occipital electrodes with maximal activation O1, O2 and Oz.
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