The effects of L-theanine on alpha-band oscillatory brain activity during a visuo-spatial attention task.
Background/Objectives Ingestion of the non-proteinic amino acid L-theanine (gamma-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.
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.
Manuel
M
Gomez-Ramirez
Simon P
SP
Kelly
Jennifer L
JL
Montesi
John J
JJ
Foxe
D000513:Alpha Rhythm / Q000187:drug effects*; D000704:Analysis of Variance; D001288:Attention / Q000187:drug effects* / Q000502:physiology; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D003463:Cues; D004569:Electroencephalography; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D005260:Female; D005971:Glutamates / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D010507:Periodicity; D013028:Space Perception / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D014796:Visual Perception / Q000187:drug effects / Q000502:physiology; D055815:Young Adult
D018690:Excitatory Amino Acid Agonists; D005971:Glutamates; C026166:theanine