Article

The Effects of L: -theanine on Alpha-Band Oscillatory Brain Activity During a Visuo-Spatial Attention Task

Program in Cognitive Neuroscience and Schizophrenia, The Cognitive Neurophysiology Laboratory, Nathan S. Kline Institute for Psychiatric Research, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA.
Brain Topography (Impact Factor: 3.47). 06/2009; 22(1):44-51. DOI: 10.1007/s10548-008-0068-z
Source: PubMed

ABSTRACT

Background/Objectives Ingestion of the non-proteinic amino acid l-theanine (γ-glutamylethylamide) has been shown to influence oscillatory brain activity in the alpha band (8–14 Hz) in humans
during resting electroencephalographic (EEG) recordings and also during cognitive task performance. We have previously shown
that ingestion of a 250-mg dose of l-theanine significantly reduced tonic (background) alpha power during a demanding intersensory (auditory-visual) attentional cueing task. Further, cue-related
phasic changes in alpha power, indexing the shorter-term anticipatory biasing of attention between modalities, were stronger on
l-theanine compared to placebo. This form of cue-contingent phasic alpha activity is also known to index attentional biasing
within visual space. Specifically, when a relevant location is pre-cued, anticipatory alpha power increases contralateral
to the location to be ignored. Here we investigate whether the effects of l-theanine on tonic and phasic alpha activity, found previously during intersensory attentional deployment, occur also during
a visuospatial task. Subjects/Methods 168-channel EEG data were recorded from thirteen neurologically normal individuals while engaged in a highly demanding visuo-spatial
attention task. Participants underwent testing on two separate days, ingesting either a 250-mg colorless and tasteless solution
of l-theanine mixed with water, or a water-based solution placebo on each day in counterbalanced order. We compared the alpha-band
activity when subjects ingested l-Theanine vs. Placebo. Results We found a significant reduction in tonic alpha for the l-theanine treatment compared to placebo, which was accompanied by a shift in scalp topography, indicative of treatment-related
changes in the neural generators of oscillatory alpha activity. However, l-theanine did not measurably affect cue-related anticipatory alpha effects. Conclusions This pattern of results implies that l-theanine plays a more general role in attentional processing, facilitating longer-lasting processes responsible for sustaining
attention across the timeframe of a difficult task, rather than affecting specific moment-to-moment phasic deployment processes.

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    • "This is particularly important, as the complex functional role of resting alpha oscillatory activity is still emerging[33], and resting state alpha activity can be considered at best a crude indicator of an individuals' state of stress, anxiety or relaxation[19]. Beyond these changes in resting alpha oscillatory activity, studies to explore functional changes in brain oscillatory activity associated with L-theanine activity during cognitive task engagement have reported tonic shifts towards reduced alpha activity during attention-demanding tasks with possible phasic alpha increases facilitating the inhibition of task irrelevance, suggesting additional actions beyond those observed in a resting state343536; however, these functional changes remain to be fully characterised, particularly given the limited evidence of behavioural performance improvements on cognitive tasks associated with L-theanine administration in humans[25,26,35]. Thus, research to date suggests a potential anti-stress effect of a single dose of L-theanine in humans, with limited support for cognitive enhancing effect based on behavioural studies in humans when consumed without caffeine. "
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    ABSTRACT: L-theanine (γ-glutamylethylamide) is an amino acid found primarily in the green tea plant. This study explored the effects of an L-theanine-based nutrient drink on mood responses to a cognitive stressor. Additional measures included an assessment of cognitive performance and resting state alpha oscillatory activity using magnetoencephalography (MEG). Thirty-four healthy adults aged 18–40 participated in this double-blind, placebo-controlled, balanced crossover study. The primary outcome measure, subjective stress response to a multitasking cognitive stressor, was significantly reduced one hour after administration of the L-theanine drink when compared to placebo. The salivary cortisol response to the stressor was reduced three hours post-dose following active treatment. No treatment-related cognitive performance changes were observed. Resting state alpha oscillatory activity was significantly greater in posterior MEG sensors after active treatment compared to placebo two hours post-dose; however, this effect was only apparent for those higher in trait anxiety. This change in resting state alpha oscillatory activity was not correlated with the change in subjective stress response or the cortisol response, suggesting further research is required to assess the functional relevance of these treatment-related changes in resting alpha activity. These findings further support the anti-stress effects of L-theanine.
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    • "Detected amounts of GABA and theanine were 0.25 mg and 52 mg, respectively, in shaded white tea, while they were 0.15 mg and 17 mg in Sagara. Knowing that most human mood studies have used higher doses of theanine (for example, 200 mg in Juneja et al. [3] and Higashiyama et al. [23]; and 250 mg in Gomez-Ramirez et al. [24]), the low dose of 52 mg in shaded white tea in this study might have been insufficient. However, one previous study on the effect of theanine consumption on human brain alpha activity found significantly greater and increasing alpha activity after ingestion of 50 mg theanine compared with placebo [25]. "
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    ABSTRACT: Background Green tea has become renowned for its health benefits. In this study, we investigated the anti-stress effect of two kinds of green tea against a mental stress task load. Methods Warm water, ordinary green tea (Sagara), and shaded white tea, which contains more amino acid components than Sagara, were used as test samples in a randomized cross-over design study. Eighteen students (nine male and nine female) participated in three experimental trials on different days at intervals of seven days. Saliva was collected before beverage intake and after performing the mental stress load tasks. Concentration of chromogranin A (CgA) in the saliva was used as an index of autonomic nervous system activity. Results CgA level increased after the mental tasks, but intake of green tea inhibited this increase; the anti-stress effect was even greater after consumption of shaded white tea. Intake of shaded white tea also lowered Total Mood Disturbance (TMD) score on the Profile of Mood States (POMS); subjects in this condition tended to perform more calculations in the arithmetic task than those in the warm water treatment condition. Conclusions Salivary CgA concentration levels increased after mental stress load tasks, but ingestion of green tea inhibited this increase. This anti-stress effect was larger after the consumption of shaded white tea than after Sagara. Shaded white tea intake also lowered TMD score (POMS) and tended to improve performance on an arithmetic task compared to warm water, suggesting that shaded white tea might also improve mood during and after mental stress load.
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    • "Recently, our group performed the first investigation of the role of alpha-band oscillations in visual feature-based selective attention (Snyder and Foxe, 2010). This study aimed to expand on prior research in selective attention which had shown that alpha-band power increases index the degree of attentional suppression in visuospatial attention tasks (Worden et al., 2000; Sauseng et al., 2005; Yamagishi et al., 2005; Kelly et al., 2006, 2009, 2010; Thut et al., 2006; Rihs et al., 2007; Gomez-Ramirez et al., 2009), intersensory attention tasks (Foxe et al., 1998; Fu et al., 2001; Gomez- Ramirez et al., 2007), sustained visual attention tasks (Dockree et al., 2007; O'Connell et al., 2009) and audiospatial attention tasks (Kerlin et al., 2010; Banerjee et al., in press). We asked if alpha-band mediated suppression would be observed in a feature-based selective attention task. "
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