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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
In Alzheimer’s disease, neuritic plaque and neurofibrillary tangles form in the olfactory bulb, olfactory tract, anterior olfactory nucleus, prepyriform cortex, uncus, and corticomedial part of the amygdaloid nucleus (Serby, Larson, and Kalkstein 1992). In normal anatomy, the anterior olfactory nucleus, the uncus, and the corticomedial part of the amygdaloid nucleus all receive afferent input from the olfactory bulb. In the entorhinal cortex, layer II stellate cells, which are the endpoint for the lateral olfactory tract, are lost. This is clinically relevant since secondary connections of the olfactory cortex are involved with memory and cognition, including the amygdala, the dorsal medial nucleus of the thalamus, and the hippocampus.
Chemosensory Malingering
Published in Alan R. Hirsch, Neurological Malingering, 2018
The anterior olfactory nucleus receives afferent fibers from the olfactory tract and projects efferent fibers, decussating in the anterior commissure, and synapsing in the contralateral olfactory bulb. Efferent projections from the anterior olfactory nucleus, nondecussating, synapse on internal granular cells of the ipsilateral olfactory bulb.
Discussions (D)
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
One might expect that such inconsistencies would be limited to textbooks that do not also contain the term “olfactory stalk (or peduncle).” In at least two cases, however, the additional term did not prevent inconsistency. Martinez Martinez uses the term “olfactory peduncle” in the usual manner and states that the anterior olfactory nucleus “accompanies the olfactory tract” (1982, p. 283). However, in the next sentence, he includes the “neurons of the anterior olfactory nucleus” as part of the olfactory tract. Similarly, Crosby, Humphrey, and Lauer (1962) most often use the term “olfactory stalk” in the usual manner and at one place state that the anterior olfactory nucleus is “present throughout the olfactory stalk” (p. 416); elsewhere, however, they list “the olfactory bulb and stalk” and “the anterior olfactory nucleus” as separate rhinencephalic structures (p. 412).
Investigational drugs for the treatment of olfactory dysfunction
Published in Expert Opinion on Investigational Drugs, 2022
Arianna Di Stadio, Cinzia Severini, Andrea Colizza, Marco De Vincentiis, Ignazio La Mantia
The neuroepithelium is connected through the axons of the ORN to the olfactory bulb, which contains glomerulus, mitral cells and tufted relay neurons. The axons converge in the glomerulus to form the first cranial nerve (olfactory nerve). The glomerulus is connected by synapses to the mitral cells; the latter together with the tufted relay neurons forms the olfactory tract. This structure bifurcates in the medial and lateral olfactory stria (y inverted-shaped). The olfactory stimulus is conducted through these structures up to the piriform cortex, the periamygdaloid cortex, the olfactory tuberculosis and the anterior olfactory nucleus. The primary olfactory cortex is formed by the medial and lateral olfactory stria and the anterior perforated substance. The lateral olfactory stria is extended posteriorly giving origin to the entorhinal area which, together with the uncus, forms the secondary olfactory cortex, also known as the orbitofrontal cortex (Figure 2). This area is straightly related to memory. The primary cortex is responsible for the active perception of the sense of smell, while the secondary one is the portion where the smell perception is integrated with emotions and memory.
Nose-to-brain drug delivery for the treatment of Alzheimer’s disease: current advancements and challenges
Published in Expert Opinion on Drug Delivery, 2022
Prabakaran A, Mukta Agrawal, Mithun Rajendra Dethe, Hafiz Ahmed, Awesh Yadav, Umesh Gupta, Amit Alexander
The olfactory nerve pathway is a direct and primary route of drug transport from the nasal cavity to the brain. Based on the nature of drug and cellular structure there are two mechanisms of drug transport including intracellular and extracellular paths. The intracellular path utilizes olfactory neurons usually for lipophilic moieties, while extracellular passage of hydrophilic or polar drugs takes place through olfactory epithelial cells [18,19]. The intracellular passage is a slower mode of drug transport to the brain which takes around 24 h, it is also considered as intraneural path 3. The axonal end of olfactory neurons starts from the mucus layer of olfactory epithelium and ends in cells of the mitral valve at the olfactory bulb by crossing the cribriform plate of lamina propria. This region is filled with CSF, and neurons are surrounded by olfactory ensheathing cells. This olfactory nerve channel is expanded to other different regions of the brain like piriform cortex, anterior olfactory nucleus, olfactory bundle, and hypothalamus [20]. In intracellular transport, the drug is taken up by the neurons via endocytosis from the olfactory epithelial cells and then it passes through the nerve channels and enters the olfactory and other regions of the brain. Besides, transcellular pathway involves drug transfer through passive diffusion, receptor mediated endocytosis, fluid phase endocytosis, etc. This mode is suitable for the passage of highly lipophilic molecules.
Gender difference in circadian clock responses for social interaction with conspecific of the opposite-sex
Published in Chronobiology International, 2021
Pratishtha Sonker, Muniyandi Singaravel
Recent studies suggest that olfactory cues play an important role in chemical communication and lead to changes in behavior during social interaction (Kelliher and Wersinger 2009). The olfactory bulb (OB) seems necessary for the resetting of the circadian clock during olfactory processing of cues, as bulbectomy abolishes socially enhanced re-entrainment but not photic re-entrainment (Goel and Lee 1997). Further, a suprachiasmatic nucleus (SCN)-independent olfactory clock regulates olfactory cues (Abraham et al. 2005; Granados-Fuentes et al. 2004, 2006). Studies on mice have showed that the OB also possesses a circadian clock that shows rhythmic oscillation in the expression of the core clock gene period-1 (per-1), and odor-induced c-fos gene, even after ablation of the SCN (Granados-Fuentes et al. 2004, 2006). It also drives the rhythm of the genetic expression of clock genes in the piriform cortex and controls olfactory responses (Granados-Fuentes et al. 2006). During chemical communication, olfactory sensory neurons bind with odorants and transduce olfactory information via olfactory marker protein (OMP) to the OB (Kass et al. 2013; Reisert et al. 2007). Thereafter, the olfactory information is conveyed from the OB to the piriform cortex, anterior olfactory nucleus, amygdala, and hypothalamus, which finally alters physiological and behavioral activities (Rodriguez and Boehm 2009). The OB may send direct or indirect signals to the SCN to coordinate other daily behavior (Guilding and Piggins 2007; Krout et al. 2002; Palouzier-Paulignan et al. 2012).