This book brings together the body of empirical findings and theoretical interpretations of the tip of the tongue (TOT) experience - when a well-known or familiar word cannot immediately be recalled. ...Although research has been published on TOTs for over a century, the experience retains its fascination for both cognitive and linguistic researchers.
After a review of various research procedures used to study TOTs, the book offers a summary of attempts to manipulate this rare cognitive experience through cue and prime procedures. Various aspects of the inaccessible target word are frequently available - such as first letter and syllable number - even in the absence of actual retrieval, and the book explores the implications of these bits of target-word information for mechanisms for word storage and retrieval. It also examines: what characteristics of a word make it potentially more vulnerable to a TOT; why words related to the target word (called "interlopers") often come to mind; the recovery process, when the momentarily-inaccessible word is recovered shortly after the TOT is first experienced; and efforts to evaluate individual differences in the likelihood to experience TOTs.
Hippocampal neural stem-cell injury during whole-brain radiotherapy (WBRT) may play a role in memory decline. Intensity-modulated radiotherapy can be used to avoid conformally the hippocampal neural ...stem-cell compartment during WBRT (HA-WBRT). RTOG 0933 was a single-arm phase II study of HA-WBRT for brain metastases with prespecified comparison with a historical control of patients treated with WBRT without hippocampal avoidance.
Eligible adult patients with brain metastases received HA-WBRT to 30 Gy in 10 fractions. Standardized cognitive function and quality-of-life (QOL) assessments were performed at baseline and 2, 4, and 6 months. The primary end point was the Hopkins Verbal Learning Test-Revised Delayed Recall (HVLT-R DR) at 4 months. The historical control demonstrated a 30% mean relative decline in HVLT-R DR from baseline to 4 months. To detect a mean relative decline ≤ 15% in HVLT-R DR after HA-WBRT, 51 analyzable patients were required to ensure 80% statistical power with α = 0.05.
Of 113 patients accrued from March 2011 through November 2012, 42 patients were analyzable at 4 months. Mean relative decline in HVLT-R DR from baseline to 4 months was 7.0% (95% CI, -4.7% to 18.7%), significantly lower in comparison with the historical control (P < .001). No decline in QOL scores was observed. Two grade 3 toxicities and no grade 4 to 5 toxicities were reported. Median survival was 6.8 months.
Conformal avoidance of the hippocampus during WBRT is associated with preservation of memory and QOL as compared with historical series.
Cognitive decline remains an unaddressed problem for the elderly. We show that myelination is highly active in young mice and greatly inhibited in aged mice, coinciding with spatial memory deficits. ...Inhibiting myelination by deletion of Olig2 in oligodendrocyte precursor cells impairs spatial memory in young mice, while enhancing myelination by deleting the muscarinic acetylcholine receptor 1 in oligodendrocyte precursor cells, or promoting oligodendroglial differentiation and myelination via clemastine treatment, rescues spatial memory decline during aging.
Over 50% of patients who survive neuroinvasive infection with West Nile virus (WNV) exhibit chronic cognitive sequelae. Although thousands of cases of WNV-mediated memory dysfunction accrue annually, ...the mechanisms responsible for these impairments are unknown. The classical complement cascade, a key component of innate immune pathogen defence, mediates synaptic pruning by microglia during early postnatal development. Here we show that viral infection of adult hippocampal neurons induces complement-mediated elimination of presynaptic terminals in a murine WNV neuroinvasive disease model. Inoculation of WNV-NS5-E218A, a WNV with a mutant NS5(E218A) protein leads to survival rates and cognitive dysfunction that mirror human WNV neuroinvasive disease. WNV-NS5-E218A-recovered mice (recovery defined as survival after acute infection) display impaired spatial learning and persistence of phagocytic microglia without loss of hippocampal neurons or volume. Hippocampi from WNV-NS5-E218A-recovered mice with poor spatial learning show increased expression of genes that drive synaptic remodelling by microglia via complement. C1QA was upregulated and localized to microglia, infected neurons and presynaptic terminals during WNV neuroinvasive disease. Murine and human WNV neuroinvasive disease post-mortem samples exhibit loss of hippocampal CA3 presynaptic terminals, and murine studies revealed microglial engulfment of presynaptic terminals during acute infection and after recovery. Mice with fewer microglia (Il34(-/-) mice with a deficiency in IL-34 production) or deficiency in complement C3 or C3a receptor were protected from WNV-induced synaptic terminal loss. Our study provides a new murine model of WNV-induced spatial memory impairment, and identifies a potential mechanism underlying neurocognitive impairment in patients recovering from WNV neuroinvasive disease.
Cognitive impairment occurs in 40-90% of patients with systemic lupus erythematosus (SLE), which is characterized by autoantibodies to nuclear antigens, especially DNA. We discovered that a subset of ...anti-DNA antibodies, termed DNRAbs, cross reacts with the N-methyl-d-aspartate receptor (NMDAR) and enhances NMDAR signaling. In patients, DNRAb presence associates with spatial memory impairment. In a mouse model, DNRAb-mediated brain pathology proceeds through an acute phase of excitotoxic neuron loss, followed by persistent alteration in neuronal integrity and spatial memory impairment. The latter pathology becomes evident only after DNRAbs are no longer detectable in the brain. Here we investigate the mechanism of long-term neuronal dysfunction mediated by transient exposure to antibody. We show that activated microglia and C1q are critical mediators of neuronal damage. We further show that centrally acting inhibitors of angiotensin-converting enzyme (ACE) can prevent microglial activation and preserve neuronal function and cognitive performance. Thus, ACE inhibition represents a strong candidate for clinical trials aimed at mitigating cognitive dysfunction.
Cellular activity in the brain depends on the high energetic support provided by mitochondria, the cell organelles which use energy sources to generate ATP. Acute cannabinoid intoxication induces ...amnesia in humans and animals, and the activation of type-1 cannabinoid receptors present at brain mitochondria membranes (mtCB
) can directly alter mitochondrial energetic activity. Although the pathological impact of chronic mitochondrial dysfunctions in the brain is well established, the involvement of acute modulation of mitochondrial activity in high brain functions, including learning and memory, is unknown. Here, we show that acute cannabinoid-induced memory impairment in mice requires activation of hippocampal mtCB
receptors. Genetic exclusion of CB
receptors from hippocampal mitochondria prevents cannabinoid-induced reduction of mitochondrial mobility, synaptic transmission and memory formation. mtCB
receptors signal through intra-mitochondrial Gα
protein activation and consequent inhibition of soluble-adenylyl cyclase (sAC). The resulting inhibition of protein kinase A (PKA)-dependent phosphorylation of specific subunits of the mitochondrial electron transport system eventually leads to decreased cellular respiration. Hippocampal inhibition of sAC activity or manipulation of intra-mitochondrial PKA signalling or phosphorylation of the Complex I subunit NDUFS2 inhibit bioenergetic and amnesic effects of cannabinoids. Thus, the G protein-coupled mtCB
receptors regulate memory processes via modulation of mitochondrial energy metabolism. By directly linking mitochondrial activity to memory formation, these data reveal that bioenergetic processes are primary acute regulators of cognitive functions.
Accumulating evidence suggests that some dietary patterns, specifically high fat diet (HFD), increase the risk of developing sporadic Alzheimer disease (AD). Thus, interventions targeting HFD-induced ...metabolic dysfunctions may be effective in preventing the development of AD. We previously demonstrated that amyloid precursor protein (APP)-overexpressing transgenic mice fed HFD showed worsening of cognitive function when compared with control APP mice on normal diet. Moreover, we reported that voluntary exercise ameliorates HFD-induced memory impairment and β-amyloid (Aβ) deposition. In the present study, we conducted diet control to ameliorate the metabolic abnormality caused by HFD on APP transgenic mice and compared the effect of diet control on cognitive function with that of voluntary exercise as well as that of combined (diet control plus exercise) treatment. Surprisingly, we found that exercise was more effective than diet control, although both exercise and diet control ameliorated HFD-induced memory deficit and Aβ deposition. The production of Aβ was not different between the exercise- and the diet control-treated mice. On the other hand, exercise specifically strengthened the activity of neprilysin, the Aβ-degrading enzyme, the level of which was significantly correlated with that of deposited Aβ in our mice. Notably, the effect of the combination treatment (exercise and diet control) on memory and amyloid pathology was not significantly different from that of exercise alone. These studies provide solid evidence that exercise is a useful intervention to rescue HFD-induced aggravation of cognitive decline in transgenic model mice of AD.
Background: Exercise and diet control are fundamental approaches to metabolic conditions caused by high fat diet (HFD).
Results: HFD-induced memory deficit and Aβ deposition were more ameliorated in the exercise- than in the diet control-induced mice.
Conclusion: Exercise was more effective than diet control in preventing HFD-induced AD development.
Significance: Exercise has the highest priority in the prevention of AD.
Well-established studies have shown an elevated level of reactive oxygen species (ROS) that induces oxidative stress in the Alzheimer’s disease (AD) patient’s brain and an animal model of AD. Herein, ...we investigated the underlying anti-oxidant neuroprotective mechanism of natural dietary supplementation of anthocyanins extracted from Korean black beans in the amyloid precursor protein/presenilin-1 (APP/PS1) mouse model of AD. Both in vivo (APP/PS1 mice) and in vitro (mouse hippocampal HT22 cells) results demonstrated that anthocyanins regulate the phosphorylated-phosphatidylinositol 3-kinase-Akt-glycogen synthase kinase 3 beta (p-PI3K/Akt/GSK3β) pathways and consequently attenuate amyloid beta oligomer (AβO)-induced elevations in ROS level and oxidative stress via stimulating the master endogenous anti-oxidant system of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (Nrf2/HO-1) pathways and prevent apoptosis and neurodegeneration by suppressing the apoptotic and neurodegenerative markers such as activation of caspase-3 and PARP-1 expression as well as the TUNEL and Fluoro-Jade B-positive neuronal cells in the APP/PS1 mice. In vitro ApoTox-Glo™ Triplex assay results also showed that anthocyanins act as a potent anti-oxidant neuroprotective agent and reduce AβO-induced neurotoxicity in the HT22 cells via PI3K/Akt/Nrf2 signaling. Importantly, anthocyanins improve memory-related pre- and postsynaptic protein markers and memory functions in the APP/PS1 mice. In conclusion, our data suggested that consumption and supplementation of natural-derived anti-oxidant neuroprotective agent such as anthocyanins may be beneficial and suggest new dietary-supplement strategies for intervention in and prevention of progressive neurodegenerative diseases, such as AD.
The current frontline symptomatic treatment for Alzheimer's disease (AD) is whole-body upregulation of cholinergic transmission via inhibition of acetylcholinesterase. This approach leads to profound ...dose-related adverse effects. An alternative strategy is to selectively target muscarinic acetylcholine receptors, particularly the M1 muscarinic acetylcholine receptor (M1 mAChR), which was previously shown to have procognitive activity. However, developing M1 mAChR-selective orthosteric ligands has proven challenging. Here, we have shown that mouse prion disease shows many of the hallmarks of human AD, including progressive terminal neurodegeneration and memory deficits due to a disruption of hippocampal cholinergic innervation. The fact that we also show that muscarinic signaling is maintained in both AD and mouse prion disease points to the latter as an excellent model for testing the efficacy of muscarinic pharmacological entities. The memory deficits we observed in mouse prion disease were completely restored by treatment with benzyl quinolone carboxylic acid (BQCA) and benzoquinazoline-12 (BQZ-12), two highly selective positive allosteric modulators (PAMs) of M1 mAChRs. Furthermore, prolonged exposure to BQCA markedly extended the lifespan of diseased mice. Thus, enhancing hippocampal muscarinic signaling using M1 mAChR PAMs restored memory loss and slowed the progression of mouse prion disease, indicating that this ligand type may have clinical benefit in diseases showing defective cholinergic transmission, such as AD.
The development of novel therapeutics to prevent cognitive decline of Alzheimer's disease (AD) is facing paramount difficulties since the translational efficacy of rodent models did not resulted in ...better clinical results. Currently approved treatments, including the acetylcholinesterase inhibitor donepezil (DON) and the N-methyl-D-aspartate antagonist memantine (MEM) provide marginal therapeutic benefits to AD patients. There is an urgent need to develop a predictive animal model that is phylogenetically proximal to humans to achieve better translation. The non-human primate grey mouse lemur (Microcebus murinus) is increasingly used in aging research, but there is no published results related to the impact of known pharmacological treatments on age-related cognitive impairment observed in this primate. In the present study we investigated the effects of DON and MEM on sleep-deprivation (SD)-induced memory impairment in young and aged male mouse lemurs. In particular, spatial memory impairment was evaluated using a circular platform task after 8 h of total SD. Acute single doses of DON or MEM (0.1 and 1mg/kg) or vehicle were administered intraperitoneally 3 h before the cognitive task during the SD procedure. Results indicated that both doses of DON were able to prevent the SD-induced deficits in retrieval of spatial memory as compared to vehicle-treated animals, both in young and aged animals Likewise, MEM show a similar profile at 1 mg/kg but not at 0.1mg/kg. Taken together, these results indicate that two widely used drugs for mitigating cognitive deficits in AD were partially effective in sleep deprived mouse lemurs, which further support the translational potential of this animal model. Our findings demonstrate the utility of this primate model for further testing cognitive enhancing drugs in development for AD or other neuropsychiatric conditions.
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