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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