The Effects of l theanine on Alpha-Band Oscillatory Brain Activity During a VisuoSpatial 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: 2.52). 01/2009; 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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Available from: John J Foxe, Aug 02, 2015
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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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    ABSTRACT: Evidence indicates that when one feature of an object is specifically attended, other task-irrelevant features of that object also receive enhanced processing, presumably as a result of automatic binding processes. On the other hand, evidence also shows that attention can be selectively biased in favor of processing one feature at the expense of processing others. Thus, binding invokes combinatorial processing of related features whereas selective attention emphasizes differential processing. We hypothesized that binding and selective feature-based attention depend on a common resource and therefore might show interference effects. The current study tested this by manipulating binding demands while human participants directed their attention to the color or motion of moving random dot stimuli. Response time measures showed that effects of biased attention were reduced when binding demands were increased. This finding supports the thesis that binding relies, at least in part, upon the same mechanisms invoked by preparatory biasing of selective attention.
    Cortex 05/2011; 48(8):1035-42. DOI:10.1016/j.cortex.2011.05.003 · 6.04 Impact Factor
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    • "We probed anticipatory activity in lower-tier visual areas by measuring a broadband ERP component known as the LDAP (latedirecting attention positivity), defined by relatively positive amplitude contralateral to the direction of a central spatial cue (Harter et al., 1989; Hopf & Mangun, 2000), as well as lateralization of alpha-band (8–14 Hz) amplitude to the visual hemisphere ipsilateral to cue direction (Worden et al., 2000). Both the LDAP and alpha lateralization have been associated with the anticipatory modulation of excitability in early visual areas responsible for processing an upcoming target (Worden et al., 2000; Kelly et al., 2005, 2006, 2009; Talsma et al., 2005; Simpson et al., 2006; Thut et al., 2006; Gomez-Ramirez et al., 2009). In addition, we tested for effects on two other spatially selective (i.e. "
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    ABSTRACT: When preparing to make a saccadic eye movement in a cued direction, perception of stimuli at the target location is enhanced, just as it is when attention is covertly deployed there. Accordingly, the timing and anatomical sources of preparatory brain activity accompanying shifts of covert attention and saccade preparation tend to exhibit a large degree of overlap. However, there is evidence that preparatory processes are modulated by the foreknowledge of visual distractor competition during covert attention, and it is unknown whether eye movement preparation undergoes equivalent modulation. Here we examine preparatory processes in the electroencephalogram of human participants during four blocked versions of a spatial cueing task, requiring either covert detection or saccade execution, and either containing a distractor or not. As in previous work, a typical pattern of spatially selective occipital, parietal and frontal activity was seen in all task versions. However, whereas distractor presence called on an enhancement of spatially selective visual cortical modulation during covert attention, it instead called on increased activity over frontomedial oculomotor areas in the case of overt saccade preparation. We conclude that, although advance orienting signals may be similar in character during overt and covert conditions, the pattern by which these signals are modulated to ameliorate the behavioral costs of distractor competition is highly distinct, pointing to a degree of separability between the overt and covert systems.
    European Journal of Neuroscience 05/2010; 31(9):1690-700. DOI:10.1111/j.1460-9568.2010.07219.x · 3.67 Impact Factor
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    • "The present study adds to a long line of demonstrations of the spatial biasing effect (Worden et al., 2000; Kelly et al., 2005, 2006; Sauseng et al., 2005; Thut et al., 2006; Doesburg & Ward, 2007; Rihs et al., 2007, 2009; Doesburg et al., 2008; Gomez-Ramirez et al., 2009). Moreover, attentional biasing of alpha is not only observed for spatial deployments but also for deployments between sensory modalities; when cued to attend to the visual modality, a sustained pre-target decrease in alpha power occurs, whereas alpha is relatively increased on attention deployment to the auditory modality, when suppression of visual distracters is required for task performance (Foxe et al., 1998; Fu et al., 2001; Gomez-Ramirez et al., 2007). "
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    ABSTRACT: Cueing relevant spatial locations in advance of a visual target results in modulated processing of that target as a consequence of anticipatory attentional deployment, the neural signatures of which remain to be fully elucidated. A set of electrophysiological processes has been established as candidate markers of the invocation and maintenance of attentional bias in humans. These include spatially-selective event-related potential (ERP) components over the lateral parietal (around 200-300 ms post-cue), frontal (300-500 ms) and ventral visual (> 500 ms) cortex, as well as oscillatory amplitude changes in the alpha band (8-14 Hz). Here, we interrogated the roles played by these anticipatory processes in attentional orienting by testing for links with subsequent behavioral performance. We found that both target discriminability (d') and reaction times were significantly predicted on a trial-by-trial basis by lateralization of alpha-band amplitude in the 500 ms preceding the target, with improved speed and accuracy resulting from a greater relative decrease in alpha over the contralateral visual cortex. Reaction time was also predicted by a late posterior contralateral positivity in the broad-band ERP in the same time period, but this did not influence d'. In a further analysis we sought to identify the control signals involved in generating the anticipatory bias, by testing earlier broad-band ERP amplitude for covariation with alpha lateralization. We found that stronger alpha biasing was associated with a greater bilateral frontal positivity at approximately 390 ms but not with differential amplitude across hemispheres in any time period. Thus, during the establishment of an anticipatory spatial bias, while the expected target location is strongly encoded in lateralized activity in parietal and frontal areas, a distinct non-spatial control process seems to regulate the strength of the bias.
    European Journal of Neuroscience 11/2009; 30(11):2224-34. DOI:10.1111/j.1460-9568.2009.06980.x · 3.67 Impact Factor
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