The Exercise Effect on Mental Health in Older Adults
Henning Budde, Mirko Wegner in The Exercise Effect on Mental Health, 2018
On the brain level, grey matter and white matter volumes decrease with age. Declining grey matter volume has been related to a decrease in the quality and quantity of connections between neurons (Peters 2002). Particularly, dendritic branches and spines show age-related decline. Further, a reduction of blood capillaries and glial cells contributes to brain volume decline. Strongest brain volume decline is observed in the caudate nucleus (as part of the basal ganglia), the cerebellum, the hippocampus, and the PFC, and these changes are well correlated to deficits in executive control and memory processes. Spatial memory seems to be particularly sensitive to a loss of axodendritic synapses in the dentate gyrus. On the contrary, there is much less decline in the limbic system and occipital (visual) cortex (Park & Reuter-Lorenz 2009; Raz & Rodrigue 2006). Also, the microstructure of the white matter changes with age. Density and integrity of axons as well as their myelinization get impaired and are often regarded as basis for slowed and less efficient processing of cognitive, motor, and sensory information.
The Stress System
Len Wisneski in The Scientific Basis of Integrative Health, 2017
Chronic stress can be devastating to the brain. As the brain is continuously bathed in cortisol, the hippocampus begins to atrophy, causing plasticity (McEwen, 2000b). Dendrites, which increase the available area for a neuron to receive incoming information, shorten and lose their branches. In addition, neurons in a part of the hippocampus called the dentate gyrus have a suppressed neurogenesis (McEwen, 2000a; Ohl et al., 2000). This reduces the ability of the hippocampus to perform vital functions, including those involving declarative, spatial, and contextual memory. Neurons in the hippocampus actually die because of exposure to glucocorticoids, even in a petri dish (Sapolsky, 1994). The hippocampus is the first part of the brain to be affected by glucocorticoids, which is a staggering thought when you consider the level of lifetime exposure that many of us experience. Their insidious effects appear to increase with aging (Sapolsky et al., 1986). Estrogen, which ameliorates the deleterious effects of stress, decreases with age (particularly in women), which is of concern because aging brains of individuals who have endured chronic stress would be more affected by memory loss (McEwen, 2000c).
The Influence of Physical Activity on Brain Aging and Cognition: The Role of Cognitive Reserve, Thresholds for Decline, Genetic Influence, and the Investment Hypothesis
James M. Rippe in Lifestyle Medicine, 2019
Neurogenesis, the growth of new neurons in the brain, as revealed in the dentate gyrus in animals, represents an exciting finding that holds great promise for medicine since the appearance of new neurons in the human hippocampus—the brain region most affected by AD dementia. This finding suggests resilience to the pathology (i.e., plaques and tangles) through participation in physical activity. In a classic study, van Praag, Kemperman, and Gage6 reported that neurogenesis in adult mice occurred in response to wheel running. After controlling for the effects of environment, they determined that physical activity alone was responsible for the observed proliferation of neurons in the dentate gyrus.6 In addition, van Praag, Christie, Sejnowski, and Gage determined that the appearance of new hippocampal cells in adult mice housed with running wheels was associated with improved cognition, as shown in performance on the Morris Water Maze and enhanced LTP when compared to controls in standard housing.67
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
It has been shown that newly generated granule cells in the adult dentate gyrus normally have transient basal dendrites [60]. However, there are numerous reports that a significant fraction of newly generated DGCs exhibited persistent abnormal morphological features in the form of basal dendrites after adult seizures [40,61–63]. Walter et al. evoked pilocarpine-induced seizures and applied a technique involving cell birth-dating by BrdU in transgenic mice expressing green fluorescent protein in DGCs; they showed that almost 50% of immature granule cells possessed aberrant hilar basal dendrites whereas only a few (9%) mature granule cells possessed basal dendrites. In addition, <5% of neurons including both newly generated DGCs and mature DGCs from normal animals exhibited abnormalities in dendrites [63]. Importantly, it was demonstrated that mossy fibers were presynaptic to hilar basal dendrites derived from newly generated DGCs and stubby spines and immature synapses appeared as early as 4–5 d after adult seizures [64,65]. In comparison, no synapses were found in those transient basal dendrites in control rats [65]. These results indicated that basal dendrites arising from newly generated DGCs might facilitate the reception of a more excessive, recurrent synaptic input from aberrantly sprouted mossy fibers after seizures, and contribute to an increase in the excitability of the hippocampal network [66].
Cerebrospinal fluid proteomics reveal potential protein targets of JiaWeiSiNiSan in preventing chronic psychological stress damage
Published in Pharmaceutical Biology, 2021
Han-Zhang Wang, Wu-Long Luo, Ning-Xi Zeng, Hui-Zhen Li, Ling Li, Can Yan, Li-Li Wu
Adult neurogenesis is a common feature of the dentate gyrus in mammals and is divided into three main parts: cell proliferation, neuronal differentiation and cell survival. In the immunofluorescence experiment, Brdu/Doublecortin (DCX) co-labelling new nerve cells and neurons were used to reflect the number of neural precursor cells in the DG area of the hippocampus. The decrease of positive cells indicated that the proliferation and differentiation ability of neural stem cells reduced and neurogenesis dysfunction. As shown in Figure 7, compared with the CON group, the number of BrdU/DCX positive cells in DG of the CUMS group reduced significantly (p < 0.05). Compared with the CUMS group, JSWNS significantly increased the number of BrdU/DCX positive cells in DG (p < 0.01). It indicates that JWSNS treatment could alleviate CUMS-induced neurogenesis dysfunction in DG.
Acute psychosocial stress during retrieval impairs pattern separation processes on an episodic memory task
Published in Stress, 2020
Jonas P. Nitschke, Lisa-Marie Giorgio, Oliwia Zaborowska, Signy Sheldon
To consider the mechanism by which stress affected lure discrimination, we turn to the finding that stress effects on memory retrieval are due to the release of cortisol targeting the hippocampus and involved pathways (Gagnon et al., 2019). Although both pattern competition and separation rely on the hippocampus, it could be that these processes are dependent to different extents on the integrity of hippocampal subfields, which are targeted in differently ways by cortisol. Specifically, pattern separation has been linked to the functioning of the dentate gyrus (Rolls, 2016), an area particularly vulnerable to the pathophysiological changes in response to cortisol release (McEwen et al., 2016). Thus, we speculate that stress during retrieval is impacted functioning of this subfield, an interpretation that fits with work reporting that deficits to hippocampal function in chronic stress disorders alter pattern separation abilities from dentate gyrus alterations (Aimone, Deng, & Gage, 2011; Yassa et al., 2011). Since we did not collected measure of hippocampal function in this study, future neuroimaging studies can test if stress induced cortisol release at retrieval targets specific aspects of the hippocampus. More generally, the stress cortisol response is known to affect areas outside the hippocampus known to be involved in executive functioning also important in successful retrieval (e.g. Shields, Sazma, & Yonelinas, 2016). Thus, future studies can establish the specificity of neurocognitive processes underlying the reported mnemonic discrimination deficit.
Related Knowledge Centers
- Adult Neurogenesis
- Episodic Memory
- Subiculum
- Temporal Lobe
- Hippocampus
- Brain
- Hippocampal Formation
- Trisynaptic Circuit
- Subventricular Zone
- Striatum