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Cells Sep 2022In mammals, neurogenesis occurs during both embryonic and postnatal development. In eutherians, most brain structures develop embryonically; conversely, in marsupials, a... (Review)
Review
In mammals, neurogenesis occurs during both embryonic and postnatal development. In eutherians, most brain structures develop embryonically; conversely, in marsupials, a number of brain structures develop after birth. The exception is the generation of granule cells in the dentate gyrus, olfactory bulb, and cerebellum of eutherian species. The formation of these structures starts during embryogenesis and continues postnatally. In both eutherians and marsupials, neurogenesis continues in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus of the hippocampal formation throughout life. The majority of proliferated cells from the SVZ migrate to the olfactory bulb, whereas, in the dentate gyrus, cells reside within this structure after division and differentiation into neurons. A key aim of this review is to evaluate advances in understanding developmental neurogenesis that occurs postnatally in both marsupials and eutherians, with a particular emphasis on the generation of granule cells during the formation of the olfactory bulb, dentate gyrus, and cerebellum. We debate the significance of immature neurons in the piriform cortex of young mammals. We also synthesize the knowledge of adult neurogenesis in the olfactory bulb and the dentate gyrus of marsupials by considering whether adult-born neurons are essential for the functioning of a given area.
Topics: Animals; Dentate Gyrus; Eutheria; Mammals; Marsupialia; Neurogenesis
PubMed: 36078144
DOI: 10.3390/cells11172735 -
Brain Research Aug 1994Recent research has shown that olfactory stimuli such as toluene vapor, but not visual, auditory, tactile or gustatory stimuli, elicit a burst of fast waves (15-30 Hz)...
Recent research has shown that olfactory stimuli such as toluene vapor, but not visual, auditory, tactile or gustatory stimuli, elicit a burst of fast waves (15-30 Hz) in the hilus of the dentate gyrus in waking rats. In urethane-anaesthetized rats, toluene odors elicit similar fast waves. The present study shows that noxious stimulation (tail clamp) produces a blockade of spontaneous slow waves (1-12 Hz) in the hilus of the dentate gyrus but does not increase fast wave activity in urethane-anaesthetized rats. This slow wave blockade, which resembles neocortical activation, is independent of olfaction since it is not affected by tracheotomy. In contrast, tracheotomy abolishes the fast wave response to toluene presentation to the snout unless the toluene vapor is drawn into the nasal passages by suction at the rostral end of the severed trachea. Both the toluene odor-induced fast wave and the tail clamp-induced activation responses are abolished by scopolamine hydrobromide (5.0 mg/kg, i.p.) but not by scopolamine methyl bromide (5.0 mg/kg, i.p.) which does not cross the blood-brain barrier. However, evoked potentials elicited in the dentate hilus by single pulse stimulation of the olfactory bulb are not blocked by scopolamine in urethane-anaesthetized rats. The results suggest that several different types of electrical activity in the hippocampal formation are mediated by cholinergic inputs and that the dentate gyrus plays a role in olfaction.
Topics: Anesthesia; Animals; Electrophysiology; Hippocampus; Male; Muscarinic Antagonists; N-Methylscopolamine; Olfactory Bulb; Pain; Parasympatholytics; Rats; Scopolamine; Scopolamine Derivatives; Smell; Urethane
PubMed: 7953735
DOI: 10.1016/0006-8993(94)90232-1 -
Journal of Affective Disorders Jun 2022Odor identification (OI) impairment increases the risk of Alzheimer's disease and brain abnormalities in patients with late-life depression (LLD). However, it remains...
BACKGROUND
Odor identification (OI) impairment increases the risk of Alzheimer's disease and brain abnormalities in patients with late-life depression (LLD). However, it remains unclear whether abnormal functional connectivity (FC) of olfactory regions is involved in the relationship between OI impairment and dementia risk in LLD patients. The current study aims to explore the olfactory FC patterns of LLD patients and how olfactory FCs mediate the relationship between OI and cognition.
METHODS
A total of 150 participants underwent resting-state functional magnetic resonance imaging and psychometric and olfactory assessments. The primary and secondary olfactory regions were selected as regions of interest to investigate olfactory FC patterns and their association with OI and cognitive performance in LLD patients.
RESULTS
Compared with LLD patients without OI impairment and normal controls, LLD patients with OI impairment exhibited increased FC between the left orbital frontal cortex (OFC) and left calcarine gyrus, between the left OFC and right lingual gyrus, between the right OFC and right rectus gyrus, and decreased FC between the right piriform cortex and right superior parietal lobule. Additionally, these abnormal FCs were associated with scores of OI, global cognition and language function. Finally, the FC between the right piriform cortex and right superior parietal lobule exhibited a partially mediated effect on the relationship between OI and MMSE scores.
LIMITATIONS
The present study did not exclude the possible effect of drugs.
CONCLUSION
LLD patients with OI impairment exhibited more disrupted olfactory FC (a decrease in the primary olfactory cortex and an increase in the secondary olfactory cortex) than LLD patients with intact OI, and these abnormal FCs may serve as potential targets for neuromodulation in LLD patients to prevent them from developing dementia.
Topics: Alzheimer Disease; Depression; Humans; Magnetic Resonance Imaging; Prefrontal Cortex; Smell
PubMed: 35292309
DOI: 10.1016/j.jad.2022.03.014 -
Annals of Neurology Sep 2017Despite numerous studies suggesting the role of insular cortex in the processing of gustatory and olfactory inputs, the exact location of olfactogustatory representation...
OBJECTIVE
Despite numerous studies suggesting the role of insular cortex in the processing of gustatory and olfactory inputs, the exact location of olfactogustatory representation in the insula remains controversial. Here we provide a functional mapping of olfactory-gustatory responses to stimulation of the human insular cortex.
METHODS
We reviewed 651 electrical stimulations of the insula that were performed in 221 patients, using stereotactically implanted depth electrodes, during the presurgical evaluation of drug-refractory epilepsy.
RESULTS
Gustatory sensations were evoked in 15 (2.7%) of the 550 stimulations that elicited a clinical response. They were exclusively obtained after stimulation of a relatively delimited zone of insula, located in its mid-dorsal part (posterior short gyrus). Six olfactory sensations (1.1%) could be obtained during stimulations of an insular region that partially overlapped with the gustatory representation.
INTERPRETATION
Our study provides a functional mapping of gustatory representation in the insular posterior short gyrus and the first detailed description of olfactory sensations obtained by direct stimulation of mid-dorsal insula. Our data also show a spatial overlap between gustatory, olfactory, and oral somatosensory representation in the mid-dorsal insula, and suggest that this part of the insula may be an integrated oral sensory region that plays a key role in flavor perception. It also indicates that dysfunction in this region should be considered during the evaluation of gustatory and olfactory epileptic seizures. Ann Neurol 2017;82:360-370.
Topics: Adult; Brain Mapping; Cerebral Cortex; Drug Resistant Epilepsy; Electric Stimulation; Electroencephalography; Female; Humans; Male; Middle Aged; Preoperative Care; Taste; Young Adult
PubMed: 28796326
DOI: 10.1002/ana.25010 -
Frontiers in Neuroscience 2023
PubMed: 38249580
DOI: 10.3389/fnins.2023.1307844 -
Frontiers in Neuroscience 2023Experiencing chronic stress significantly increases the risk for depression. Depression is a complex disorder with varied symptoms across patients. However, feeling of...
Experiencing chronic stress significantly increases the risk for depression. Depression is a complex disorder with varied symptoms across patients. However, feeling of sadness and decreased motivation, and diminished feeling of pleasure (anhedonia) appear to be core to most depressive pathology. Odorants are potent signals that serve a critical role in social interactions, avoiding danger, and consummatory behaviors. Diminished quality of olfactory function is associated with negative effects on quality of life leading to and aggravating the symptoms of depression. Odor hedonic value (I like or I dislike this smell) is a dominant feature of olfaction and guides approach or avoidance behavior of the odor source. The neural representation of the hedonic value of odorants is carried by the granule cells in the olfactory bulb, which functions to modulate the cortical relay of olfactory information. The granule cells of the olfactory bulb and those of the dentate gyrus are the two major populations of cells in the adult brain with continued neurogenesis into adulthood. In hippocampus, decreased neurogenesis has been linked to development or maintenance of depression symptoms. Here, we hypothesize that chronic mild stress can alter olfactory hedonics through effects on the olfactory bulb neurogenesis, contributing to the broader anhedonia phenotype in stress-associated depression. To test this, mice were subjected to chronic unpredictable mild stress and then tested on measures of depressive-like behaviors, odor hedonics, and measures of olfactory neurogenesis. Chronic unpredictable mild stress led to a selective effect on odor hedonics, diminishing attraction to pleasant but not unpleasant odorants, an effect that was accompanied by a specific decrease in adult neurogenesis and of the percentage of adult-born cells responding to pleasant odorants in the olfactory bulb.
PubMed: 37600017
DOI: 10.3389/fnins.2023.1224941 -
Learning & Memory (Cold Spring Harbor,... Nov 2013In the adult mammalian brain, newly generated neurons are continuously incorporated into two networks: interneurons born in the subventricular zone migrate to the... (Review)
Review
In the adult mammalian brain, newly generated neurons are continuously incorporated into two networks: interneurons born in the subventricular zone migrate to the olfactory bulb, whereas the dentate gyrus (DG) of the hippocampus integrates locally born principal neurons. That the rest of the mammalian brain loses significant neurogenic capacity after the perinatal period suggests that unique aspects of the structure and function of DG and olfactory bulb circuits allow them to benefit from the adult generation of neurons. In this review, we consider the distinctive features of the DG that may account for it being able to profit from this singular form of neural plasticity. Approaches to the problem of neurogenesis are grouped as "bottom-up," where the phenotype of adult-born granule cells is contrasted to that of mature developmentally born granule cells, and "top-down," where the impact of altering the amount of neurogenesis on behavior is examined. We end by considering the primary implications of these two approaches and future directions.
Topics: Animals; Dentate Gyrus; Neurogenesis; Neurons
PubMed: 24255101
DOI: 10.1101/lm.026542.112 -
Acta Radiologica (Stockholm, Sweden :... Sep 2023Bipolar disorder (BD) is a mental health disorder.
BACKGROUND
Bipolar disorder (BD) is a mental health disorder.
PURPOSE
To investigate the peripheric and central olfactory measurements in patients with BD using magnetic resonance imaging (MRI).
MATERIAL AND METHODS
This study was conducted retrospectively. Group 1 consisted of 27 euthymic patients with BD (14 men, 13 women) and Group 2 consisted of 27 healthy controls (14 men, 13 women). Olfactory bulb (OB) volume and olfactory sulcus (OS) depth (peripheric), and corpus amygdala and insular gyrus area (central) measurements were performed using cranial MRI.
RESULTS
OB volume and OS depth value of the bipolar group were lower than the control group, but there were no significant differences between the groups ( > 0.05). The corpus amygdala and left insular gyrus area of the bipolar group were significantly lower than those in the control group ( < 0.05). There were positive correlations between OB volumes and OS depths, the insular gyrus areas, and the corpus amygdala areas ( < 0.05). As the number of depressive episodes and duration of illness increased in bipolar patients, the depth of the sulcus decreased ( < 0.05).
CONCLUSION
In the present study a correlation was detected between OB volumes and the structures, known as emotional processing (e.g. insular gyrus area, corpus amygdala), and clinical features. Accordingly, new treatment techniques, such as olfactory training, may be considered an option in the treatment of such patients with BD.
Topics: Male; Humans; Female; Bipolar Disorder; Olfaction Disorders; Retrospective Studies; Smell; Amygdala; Magnetic Resonance Imaging
PubMed: 37312533
DOI: 10.1177/02841851231179174 -
Journal of Physiology, Paris 1996Olfactory recognition which occurs in the context pregnancy block by male pheromones is acquired with one-trial learning contingent on mating. A memory trace is... (Review)
Review
Olfactory recognition which occurs in the context pregnancy block by male pheromones is acquired with one-trial learning contingent on mating. A memory trace is established in the accessory bulb (AOB) and is represented by a gain in Gaba-ergic feedback inhibition of granule cells on excitatory glutaminergic mitral cells. This occurs in the sub-population of mitral cells that specifically respond to an individual male's pheromones, and is dependent on noradrenaline release at mating. Although relatively simple, the AOB has both structural and functional similarities with other trilaminar neural structures involved in learning, which suggests some evolutionary conservation of mechanisms subserving memory.
Topics: Animals; Dentate Gyrus; Female; Glutamine; Hippocampus; Male; Memory; Models, Neurological; Neurons; Olfactory Bulb; Olfactory Nerve; Pheromones; Pregnancy; Smell; gamma-Aminobutyric Acid
PubMed: 9089523
DOI: 10.1016/s0928-4257(97)87929-6 -
Annual Review of Physiology 2013Modern neuroscience has demonstrated how the adult brain has the ability to profoundly remodel its neurons in response to changes in external stimuli or internal states.... (Review)
Review
Modern neuroscience has demonstrated how the adult brain has the ability to profoundly remodel its neurons in response to changes in external stimuli or internal states. However, adult brain plasticity, although possible throughout life, remains restricted mostly to subcellular levels rather than affecting the entire cell. New neurons are continuously generated in only a few areas of the adult brain-the olfactory bulb and the dentate gyrus-where they integrate into already functioning circuitry. In these regions, adult neurogenesis adds another dimension of plasticity that either complements or is redundant to the classical molecular and cellular mechanisms of plasticity. This review extracts clues regarding the contribution of adult-born neurons to the different circuits of the olfactory bulb and specifically how new neurons participate in existing computations and enable new computational functions.
Topics: Animals; Dentate Gyrus; Humans; Nerve Net; Neurogenesis; Neuronal Plasticity; Olfactory Bulb; Synapses
PubMed: 23190074
DOI: 10.1146/annurev-physiol-030212-183731