cognitive-function

Author: Gail N. Owen, and  Holly Parnell, and Eveline A. De Bruin and Jane A. Rycroft

The aim of this study was to compare 50 mg caffeine, with and without 100 mg L-theanine, on cognition and mood in healthy volunteers. The effects of these treatments on word recognition, rapid visual information processing, critical flicker fusion threshold, attention switching and mood were compared to placebo in 27 participants. Performance was measured at baseline and again 60 min and 90 min after each treatment (separated by a 7-day washout). Caffeine improved subjective alertness at 60 min and accuracy on the attention-switching task at 90 min. The L-theanine and caffeine combination improved both speed and accuracy of performance of the attention-switching task at 60 min, and reduced susceptibility to distracting information in the memory task at both 60 min and 90 min. These results replicate previous evidence which suggests that L-theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks.

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Author: Siamwala JH, and Dias PM, and Majumder S, and Joshi MK, and Sinkar VP, and Banerjee G, and Chatterjee S

Consumption of tea (Camellia sinensis) improves vascular function and is linked to lowering the risk of cardiovascular disease. Endothelial nitric oxide is the key regulator of vascular functions in endothelium. In this study, we establish that l-theanine, a non-protein amino-acid found in tea, promotes nitric oxide (NO) production in endothelial cells. l-theanine potentiated NO production in endothelial cells was evaluated using Griess reaction, NO sensitive electrode and a NO specific fluorescent probe (4-amino-5-methylamino-2',7'-difluororescein diacetate). l-Theanine induced NO production was partially attenuated in presence of l-NAME or l-NIO and completely abolished using eNOS siRNA. eNOS activation was Ca(2+) and Akt independent, as assessed by fluo-4AM and immunoblotting experiments, respectively and was associated with phosphorylation of eNOS Ser 1177. eNOS phosphorylation was inhibited in the presence of ERK1/2 inhibitor, PD-98059 and partially inhibited by PI3K inhibitor, LY-294002 and Wortmanin suggesting PI3K-ERK1/2 dependent pathway. Increased NO production was associated with vasodilation in ex ovo (chorioallantoic membrane) model. These results demonstrated that l-theanine administration in vitro activated ERK/eNOS resulting in enhanced NO production and thereby vasodilation in the artery. The results of our experiments are suggestive of l-theanine mediated vascular health benefits of tea.

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Author: Yohei Mineharu, and Akio Koizumi, and Yasuhiko Wada, and Hiroyasu Iso, and Yoshiyuki Watanabe, and Chigusa Date, and Akio Yamamoto, and Shogo Kikuchi, and Yutaka Inaba, and Hideaki Toyoshima, and Takaaki Kondo, and Akiko Tamakoshi

Background: The effects of coffee and green, black and oolong teas and caffeine intake on cardiovascular disease (CVD) mortality have not been well defined in Asian countries. Methods: To examine the relationship between consumption of these beverages and risk of mortality from CVD, we prospectively followed 76,979 individuals aged 40-79 y free of stroke, coronary heart disease (CHD), and cancer at entry. Daily consumption of beverages was assessed by questionnaires. Results: We documented 1362 deaths from strokes and 650 deaths from CHD after 1,010,787 person-years of follow-up. Compared with non-drinkers of coffee, the multivariable hazard ratios (HRs) and 95% confidence interval for those drinking 1-6 cups/wk, 1-2 cups/d and a ‰Ψ3 cups/d were 0.78 (0.50-1.20), 0.67 (0.47-0.96) and 0.45 (0.17-0.87) for strokes among men (p=0.009 for trend). Compared with non-drinkers of green tea, the multivariable HRs for those drinking 1-6 cups/wk, 1-2 cups/d, 3-5 cups/d and a ‰Ψ6 cups/d were 0.34 (0.06-1.75), 0.28 (0.07-1.11), 0.39 (0.18-0.85), and 0.42 (0.17-0.88) for CHD among women (p=0.038 for trend). As for oolong tea, the multivariable HRs of those drinking 1-6 cups/wk and a ‰Ψ1 cups/d were 1.00 (0.65-1.55) and 0.39 (0.17-0.88) for total CVD among men (p=0.049 for trend). Risk reduction for total CVD across categories of caffeine intake was most prominently observed in the second highest quintile with a 38% lower risk among men and 22% among women. Conclusions: Consumption of coffee, green tea and oolong tea and total caffeine intake was associated with a reduced risk of mortality from CVD.

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Author: René Garcia

During the last two decades numerous studies have been conducted in an attempt to correlate the mechanisms of long-term potentiation (LTP) of hippocampal synaptic transmission with those required for spatial memory formation in the hippocampus. Because stressful events block the induction of hippocampal LTP, it has been suggested that deficits in spatial learning following stress may be related to suppression of LTP-like phenomena in the hippocampus. Here I review these studies and discuss them in light of the emerging view that stress may induce changes in thresholds for synaptic plasticity necessary for both LTP induction and spatial memory formation. This phenomenon, known as metaplasticity, may involve a glucocorticoid modulation of calcium homeostasis.

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Author: Carmen Sandi

Glucocorticoids can acutely affect memory processes, with both facilitating and impairing effects having been described. Recent work has revealed that glucocorticoids may affect learning and memory processes by interacting with glutamatergic mechanisms. In this opinion article I describe different glutamatergic pathways that glucocorticoids can affect to modulate memory processes. Furthermore, glucocorticoid-glutamatergic interactions during information processing are proposed as a potential model to explain many of the diverse actions of glucocorticoids on cognition. The model suggests that direct modulation of glutamatergic pathways by glucocorticoids could serve as an important mechanism for these hormones to directly alter cognitive functions.

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Protective effect of l-theanine on chronic restraint stress-induced cognitive impairments in mice

Author: Tian X, and Sun L, and Gou L, and Ling X, and Feng Y, and Wang L, and Yin X, and Liu Y

The present work was aimed to study the protective effect of l-theanine on chronic restraint stress (CRS)-induced cognitive impairments in mice. The stress was produced by restraining the animals in well-ventilated polypropylene tubes (3.2 cm in diameter ×10.5 cm in length) for 8 h once daily for 21 consecutive days. L-theanine (2 and 4 mg/kg) was administered 30 min before the animals subjected to acute immobilized stress. At week 4, mice were subjected to Morris water maze and step-through tests to measure the cognitive function followed by oxidative parameters and corticosterone as well as catecholamines (norepinephrine and dopamine) subsequently. Our results showed that the cognitive performances in CRS group were markedly deteriorated, accompanied by noticeable alterations in oxidative parameters and catecholamine levels in the hippocampus and the cerebral cortex as well as corticosterone and catecholamine levels in the serum. However, not only did l-theanine treatment exhibit a reversal of the cognitive impairments and oxidative damage induced by CRS, but also reversed the abnormal level of corticosterone in the serum as well as the abnormal levels of catecholamines in the brain and the serum. This study indicated the protective effect of l-theanine against CRS-induced cognitive impairments in mice.

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Author: Anneleen Schallier, and Katia Vermoesen, and Ellen Loyens, and Joeri Van Liefferinge, and Yvette Michotte, and Ilse Smolders

l-Theanine, an ethylamide derivate of glutamate found in abundance in green tea, has been shown to exert beneficial actions in animal models for several neurological disorders. We here investigated for the first time the effect of l-theanine intake on seizure susceptibility using acute pilocarpine and pentylenetetrazol (PTZ) mouse models for studying, respectively, limbic seizures or primarily generalized seizures. Moreover, we studied the effect of l-theanine intake on extracellular hippocampal and cortical glutamate and gamma-aminobutyric acid (GABA) levels, using in vivomicrodialysis. Feeding mice with a 4% l-theanine solution significantly decreased their susceptibility to pilocarpine-induced seizures whereas susceptibility to PTZ-induced seizures was increased. The latter effect was linked to decreased extracellular GABA concentrations in frontal cortex.

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Author: Michael S. Ritsner, and Chanoch Miodownik, and Yael Ratner, and Tatyana Shleifer, and Maria Mar, and Leonid Pintov, and Vladimir Lerner

Objective: L-Theanine is a unique amino acid present almost exclusively in the tea plant. It possesses neuroprotective, mood-enhancing, and relaxation properties. This is a first study designed to evaluate the efficacy and tolerability of L-theanine augmentation of antipsychotic treatment of patients with chronic schizophrenia and schizoaffective disorder. Method: 60 patients with DSM-IV schizophrenia or schizoaffective disorder participated in an 8-week, double-blind, randomized, placebo-controlled study. 400 mg/d of L-theanine was added to ongoing antipsychotic treatment from February 2006 until October 2008. The outcome measures were the Positive and Negative Syndrome Scale (PANSS), the Hamilton Anxiety Rating Scale (HARS), the Cambridge Neuropsychological Test Automated Battery (CANTAB) for neurocognitive functioning, and additional measures of general functioning, side effects, and quality of life. Results: 40 patients completed the study protocol. Compared with placebo, L-theanine augmentation was associated with reduction of anxiety (P = .015; measured by the HARS scale) and positive (P = .009) and general psychopathology (P < .001) scores (measured by the PANSS 3-dimensional model). According to the 5-dimension model of psychopathology, L-theanine produced significant reductions on PANSS positive (P = .004) and activation factor (P = .006) scores compared to placebo. The effect sizes (Cohen d) for these differences ranged from modest to moderate (0.09–0.39). PANSS negative and CANTAB task scores, general functioning, side effect, and quality of life measures were not affected by L-theanine augmentation. L-Theanine was found to be a safe and well-tolerated medication. Conclusions: L-Theanine augmentation of antipsychotic therapy can ameliorate positive, activation, and anxiety symptoms in schizophrenia and schizoaffective disorder patients. Further long-term studies of L-theanine are needed to substantiate the clinically significant benefits of L-theanine augmentation.

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Author: Cohen-Zion M, and Ancoli-Israel S

Attention-Deficit Hyperactivity Disorder (ADHD) is the most common behavioral disorder of childhood. Multiple clinical and research reports suggest extensive sleep disturbances in children with ADHD, however, current data is contradictory. This paper reviewed 47 research studies (13 stimulant intervention and 34 naturalistic) on ADHD that were published since 1980. The main objectives of this review were to provide pediatric clinicians and researchers a clear and concise summary of published sleep data in children with ADHD, to provide a more accurate description of the current knowledge of the relationship between sleep and ADHD, and to provide current information on the effect of stimulant medication on sleep. Twenty-five of the reviewed studies used subjective reports of sleep, six were actigraphic studies, and 16 were overnight polysomnographic sleep studies (two of which also included Multiple Sleep Latency Tests). All participants were between the age of 3 and 19, and 60% were male. The results indicate high rates of parental reports of sleep disturbances in medicated and unmedicated children with ADHD, however, the majority of these findings have not been confirmed by objective sleep data. Although, agreement among objective studies is not absolute, the data suggest increased nighttime activity, reduced rapid eye movement sleep, and significant daytime somnolence in unmedicated children with ADHD when compared to controls. Data also suggest a possible increased prevalence of periodic limb movements in sleep in children with ADHD, however, little differences in sleep-disordered breathing. The limited number of studies, small and heterogeneous samples, and other methodological limitations make definite results difficult to determine. Future research will need to further clarify the relationship between sleep and ADHD and the effects of stimulants on sleep of children with ADHD.

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Author: Samuele Cortese and Stephen V. Faraone and Eric Konofal and Michel Lecendreux