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.
- High-density electrical mapping
ASJC Scopus subject areas
- Radiological and Ultrasound Technology
- Radiology Nuclear Medicine and imaging
- Clinical Neurology