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Chemosensory Disorders and Nutrition
Published in Alan R. Hirsch, Nutrition and Sensation, 2023
Carl M. Wahlstrom, Alan R. Hirsch, Bradley W. Whitman
Inside the olfactory bulb is a conglomeration of neuropil, yclept the glomeruli. Approximately 2,000 glomeruli reside in the olfactory bulb. Four different cell types make up the glomeruli: processes of receptor cell axons, mitral cells, tufted cells, and second-order neurons which give off collaterals to the granule cells and to cells in the periglomerular and external plexiform layers. The mitral and tufted cells form the lateral olfactory tract and establish a reverberating circuit with the granule cells. The mitral cells stimulate firing of the granule cells, which in turn inhibit firing of the mitral cells (Brodal 1969).
The Hungry Brain
Published in Emily Crews Splane, Neil E. Rowland, Anaya Mitra, Psychology of Eating, 2019
Emily Crews Splane, Neil E. Rowland, Anaya Mitra
As noted before, smell is transmitted as a cross-fiber code via axons of mitral and tufted cells in the olfactory bulb. In rodents, the olfactory bulbs are large structures relative to the brain (Figure 6.1), but in humans they are quite small appendages lying beneath the very large frontal cortex. The mitral and tufted cells of the olfactory bulb form two separate projections to the olfactory cortex, much of which is called pyriform cortex. Tufted cells project only to the anterior parts of the olfactory cortex and are thought to convey information about low intensity odors with high temporal resolution (for example, that you might use for chemotaxis – moving toward an odor source or scent), while mitral cells project to the entire extent of the olfactory cortex and may mediate more specific discriminatory or “what is it?” capacity (Mori & Sakano, 2011). This is like the dual sensory functions in other sensory systems, including vision. The pyriform cortex provides inputs to the orbitofrontal cortex (OFC; Figure 6.2) and amygdala.
Abnormalities of Smell
Published in John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie, Basic Sciences Endocrine Surgery Rhinology, 2018
Richard L. Doty, Steven M. Bromley
The olfactory bulbs are complex structures located on the ventral surface of the frontal lobes directly over the cribriform plate. The first synapse of the incoming bipolar olfactory receptor cell neurons occurs within spherical structures making up a distinct layer of the bulb – the glomeruli. A given receptor projects to only one glomerulus, and any given glomerulus appears to receive most of its input from a restricted region of the epithelium. The main afferent second-order neurons are termed mitral and tufted cells. A considerable amount of convergence of information occurs at the level of the glomeruli. The mitral and tufted cells, in turn, send collaterals that synapse within the periglomerular and external plexiform layers, resulting in ‘reverberating’ circuits in which negative and positive feedback occur. The apical dendrites of the mitral and tufted cells are influenced by interneurons and centrifugal fibres, most of which are GABAergic or dopaminergic.21
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].
Olfactory bulbectomy and raphe nucleus relationship: a new vision for well-known depression model
Published in Nordic Journal of Psychiatry, 2020
Halil Ozcan, Nazan Aydın, Mehmet Dumlu Aydın, Elif Oral, Cemal Gündoğdu, Sare Şipal, Zekai Halıcı
The OBs as electrocauterized and mechanically compressed in the study groups are shown (as shown in Base/Figure 1). In microscopic examinations of the OBs, atrophy, sclerosis of glomerular and tufted cells, and olfactory tract degeneration and volume loss were detected in the study groups (as shown in left upper corner/Figure 1). Morphologically deformed and apoptotic neurons were evaluated and counted separately. Neuronal damage considered as GABAergic neuronal loss besides the serotonergic ones, particularly in the lateral wings of the DRNs in which area about 15–20% of the total neurons are GABAergic neurons were seen (as shown in Figure 2(A,B)). The specimens were stained with S-100 for determining the morphological changes (as shown in Figure 3). Morphologically deformed neuron density of DRNs detected with S-100 was nearly the same as those apoptotic neurons detected with NSE (as shown in Figure 4). TUNEL staining was performed to determine apoptosis in the DR neurons (as shown in Figure 5). Apoptotic degeneration in GABA neurons was demonstrated with immunostaining method (as shown in Figure 6).
Olfactory nerve schwannoma: how human anatomy and electron microscopy can help to solve an intriguing scientific puzzle
Published in Ultrastructural Pathology, 2022
Fabbri Vp, Valentina Papa, Tonon C, Agati R, Toni F, Zoli M, Mazzatenta D, Fioravanti A, Badaloni F, Cenacchi G, Foschini Mp, Asioli S
Different types of neurons can be found in the olfactory bulb: mitral cells, tufted cells, granule cells, and periglomerular neurons. The projections of these neurons (especially mitral and tufted cells in the glomeruli) run dorsally and form the olfactory tract.2