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Principles of cognitive rehabilitation in TBI: An integrative neuroscience approach
Published in Mark J. Ashley, David A. Hovda, Traumatic Brain Injury, 2017
Fofi Constantinidou, Robin D. Thomas
Exciting experiments in the past two decades have demonstrated that new neurons continually form in the brain of adult animals, including primates and humans.46–50 New neurons were first found in the brains of adult songbirds in areas of the brain associated with song production. Then, new granule cells were found in the hippocampus of adult chickadees; then, in rats and primates.47 The same pattern of neuronal generation has been found in the hippocampus of adult humans.46,48 Recently in monkeys, new neurons were found to be migrating to the neocortex from stem cells in the region of the ventricles.50 Adult neurogenesis results in continual influx of neurons that are (temporarily) immature and, therefore, structurally plastic. The hope is that the immature cells can take on functions of mature, adult cells. Although this premise has not been verified yet, adult neurogenesis can have important implications for our understanding of the mechanisms of neural plasticity in general and recovery of function following brain lesions in particular.46,49,51
Neurogenesis in the Adult and Aging Brain
Published in David R. Riddle, Brain Aging, 2007
David R. Riddle, Robin J. Lichtenwalner
Interest in adult neurogenesis increased tremendously in the 1980s after Nottebohm demonstrated seasonally regulated neurogenesis in the song nuclei of songbirds and provided evidence that adult neurogenesis subserved a neural function (reviewed in [6, 7]). Nottebohm’s analyses left no doubt that tritiated thymidine labeled cells in the adult bird brain were neurons, and evidence that the production of new neurons peaks at the time birds acquire new songs provided a compelling indication that adult neurogenesis is functionally significant, at least in birds. Subsequent studies demonstrated that neurogenesis also was ongoing in the hippocampus of adult birds and that the extent of hippocampal neurogenesis correlated both seasonally and across species with seed-storing, a behavior that depends on hippocampally dependent spatial learning [8–10]. Spurred in part by the dramatic findings in avian species, interest in adult neurogenesis in mammals increased precipitously into the 1990s, with several laboratories publishing seminal investigations of the nature and extent of neurogenesis in the adult mammalian brain (e.g., [11–15]). In addition to critical studies assessing adult neurogenesis in vivo using radioactive thymidine and the thymidine analog bromodeoxyuridine (BrdU), demonstrations that cells with stem cell properties could be isolated from the adult brain established a source for new neurons in the adult brain (e.g., [16–19]). Although the debate continues regarding the extent of adult neurogenesis across brain regions and across species [20–23], clearly new neurons are continually produced in some regions of the adult mammalian brain, even in humans [24], new neurons are integrated into functional circuits, and the ongoing neuronal turnover is significant for some functions.
Cognitive Disorders and Lifestyle Change
Published in Gia Merlo, Kathy Berra, Lifestyle Nursing, 2023
Cognition is dependent on neuroplasticity (Kaliszewska et al., 2021). Neuroplasticity is the brain’s ability to adjust to structural and functional changes in response to alterations in the environment. New connections between neurons are formed in response to new experiences and learning, which induce neuronal networks to re-organize and fine-tune brain circuitry. Neurogenesis (growth and development of nervous tissue) is a neurological process supporting cognitive functioning and development. Adult neurogenesis occurs in the hippocampus, which plays a crucial role in memory, mood, and spatial learning. The brain is a complex organ that requires a substantial amount of energy called mitochondrial adenosine triphosphate (ATP). Neurons in the brain require a high level of ATP to process information. The main role of mitochondria is to produce ATP, which is cellular energy (Todorova & Blokland, 2016). Mitochondrial organelles are found in all eukaryotic cells, including neurons. Mitochondrial disorders commonly affect the brain, causing cognitive impairments. It has been shown that an increase in oxidative damage to deoxyribonucleic acid (DNA), proteins, and lipids occurs during aging. One of the major causes of neurodegeneration is neuroinflammation, a process that damages the brain’s synaptic plasticity functions (Onyango et al., 2021). The hallmarks of an aging brain include cortical atrophy, synaptic loss, low-grade chronic inflammation, and cerebrovascular pathology. The integrity of blood vessels in the brain allows for adequate cerebral blood flow (CBF). The brain is dependent on adequate CBF for mitochondrial energy metabolism. Brain neurons use 70–80% of mitochondrial energy for functions such as neurogenesis and neuroplasticity, which are important functions to the brain structures involved in cognition. Neuroinflammation, nutrition-induced dysregulation of blood–brain barrier permeability, mitochondrial dysfunction, breakdown of glucose metabolism, and hypoperfusion linked to cerebrovascular dysfunction are factors implicated as underlying causes of cognitive impairment.
Gut dysbiosis impairs hippocampal plasticity and behaviors by remodeling serum metabolome
Published in Gut Microbes, 2022
Guoqiang Liu, Quntao Yu, Bo Tan, Xiao Ke, Chen Zhang, Hao Li, Tongmei Zhang, Youming Lu
In this study, we demonstrated that gut dysbiosis in early-life impaired hippocampal neurogenesis that was restored by reconstructing a normal microbiota. Adult neurogenesis is an important process in regulating brain function and behavior. Reduction of adult neurogenesis has been associated with several psychiatric disorders, such as anxiety, depression, and memory loss.51 Neurogenesis has been reported to be orchestrated by several intrinsic and extrinsic factors, such as inflammatory cytokines, neurotransmitters, physical activity, and dietary intake.52 In addition, Ly6Chi monocytes were reported to be involved in modulating hippocampal neurogenesis in ABX-treated mice.53 Indoles, microbial metabolites of dietary tryptophan, were found to increase adult neurogenesis via the aryl hydrocarbon receptor pathway.54 Gut microbiota from chronic stress-treated mice decreased neurogenesis in healthy mice by impairing the Trp metabolism.55 In this study, the effect of gut dysbiosis on neurogenesis may be driven by multiple aspects, such as immune cell infiltration and circulating metabolites changes.
Polyunsaturated fatty acids and endocannabinoids in health and disease
Published in Nutritional Neuroscience, 2018
Hércules Rezende Freitas, Alinny Rosendo Isaac, Renato Malcher-Lopes, Bruno Lourenço Diaz, Isis Hara Trevenzoli, Ricardo Augusto De Melo Reis
Adult neurogenesis is a dynamic process that modulates synaptic plasticity in the brain and influences memory, learning and humor, occurring in response to intrinsic and environmental factors.155 Several recent reports have shown that cannabinoids play a direct modulatory role in adult neurogenesis156 and in postnatal oligodendrogenesis.157 Neurogenesis greatly influences synaptic reorganization of the olfactory bulb and hippocampal memory-dependent behavior.158 Recently, it was shown that the sustained activation of the mammalian target of rapamycin 1 (mTOR 1) is an important regulator of neurogenesis in the ventricular and subventricular zones, and the stimulation of CB1 receptors positively interferes in this pathway.159
Aberrant plasticity in the hippocampus after neonatal seizures
Published in International Journal of Neuroscience, 2018
Xiaoqian Zhang, Huiling Qu, Ying Wang, Shanshan Zhao, Ting Xiao, Chuansheng Zhao, Weiyu Teng
During the past century, it has become accepted that neural stem cells exist in two main neurogenic regions in the adult brain, the subgranular zone (SGZ) of the dentate gyrus and the subventricular zone (SVZ); these are both capable of generating new neurons continuously throughout life [1,2]. The newly generated neuroblasts in the SVZ migrate towards the olfactory bulb through the rostral migratory stream, where they differentiate into granule cells or periglomerular cells in the olfactory bulb, which reside in the granule cell layer or glomerula, respectively. The progenitor cells within the SGZ of the dentate gyrus proliferate and differentiate into dentate granule cells (DGCs), and these newly generated DGCs in turn integrate into the mature hippocampal neuronal network. Eventually, these new neurons from SVZ and SGZ appear to have similar morphological, physiological and functional features as mature neurons [3]. The process of adult neurogenesis can be influenced by a variety of physiological and pathological stimuli, including brain injury, stress, aging, genetics and exercise [4–8]. For example, seizures induced by chemicals or electrical stimulation can result in aberrant neurogenesis [9–12].