Theanine and Caffeine on Neurophysiology of Attention
Condition: L-theanine
Study type: Interventional

Summary: 
      L-theanine and caffeine are nutritional compounds that are naturally found in tea. Our recent
      findings using an EEG paradigm are consistent with the findings of others, indicating that
      intake of L-theanine and caffeine reduce the time needed for a person to differentiate
      between two visual stimuli and react to only one stimulus. In order to understand how these
      compounds give rise to these improvements, the investigators need to study how these
      compounds are related to various areas of the brain. To achieve this, the investigators plan
      to scan the brains of nine participants after they take either 1) L-theanine alone, 2)
      caffeine alone 3) the combination of both L-theanine and caffeine as compared with a placebo
      (distilled water), to see which has the greatest impact on attention and on regions in the
      brain that bring about attention.
    

Detailed description: 
      Recruitment: Participants will be recruited through advertisements in social media,
      electronic and hardcopy noticeboards at Texas Tech University (e.g. Tech Announce, campus
      bulletin boards), local media (e.g. newspapers), web-based media (e.g. Craig's list) and
      flyers placed on bulletin boards off campus. Nine participants will be recruited after
      screening for the following inclusion and exclusion criteria.

      Pre-Screening (Telephone): Individuals who express an interest in participating will be
      contacted by a graduate or an undergraduate research assistant who will administer a
      structured telephone interview to: 1) provide information related to the requirements of the
      study, along with potential risks and benefits 2) Screen for eligibility based on specific
      inclusion and exclusion criteria. All potential subjects will be informed that their
      responses will remain confidential and that taking part in the screening interview in no way
      obligates them to participate.

      The first 9 participants who meet eligibility criteria will be scheduled for their
      appointments (at Texas Tech Neuroimaging Institute; TTNI) immediately or within 48 hours of
      the telephone conversation depending on the discretion of each potential participant. Each
      participant will be required to complete 5 visits to TTNI, scheduled at least 5 days apart,
      in order to complete their participation in the study. The first visit will be 45 minutes in
      length and each of the 4 subsequent visits will be 90 minutes in length. The participants
      will be given the right to withdraw from the study at any point. In the event that a screened
      and included participant should discontinue the study prematurely, additional subjects will
      be recruited to maintain study total at 9 completers. Since the study is a cross-over design,
      all participants will be exposed to all experimental conditions (i.e. theanine, caffeine, TC
      and distilled water) in a random order.

      Measurements:

        1. Recognition Visual Reaction Time (RVRT) Task: Participants will be instructed on the
           importance of accuracy in performing the RVRT task in advance. A blue-colored background
           will be presented. Participants will be requested to press a button on a computer
           keyboard (during practice sessions) and on a fiber optic hand-held device during active
           testing sessions (in the fMRI scanner) using the index finger of the dominant hand in
           response to a white flash lasting for 30ms (target stimulus) as quickly as possible,
           while ignoring a red colored flash lasting for 30ms (distractor stimulus). During each
           run, 20±2 stimuli of each category of stimuli will be presented and the inter-stimulus
           interval will be jittered to 5000ms±3000ms. Time taken to respond to target stimuli will
           be recorded as RVRT. Omissions and responses to distractor stimuli (errors) will also be
           recorded.

        2. Scanning paradigm: Each scanning session will be scheduled for 20 minutes, comprised of
           3 runs of fMRI scans while the participants are performing the RVRT tasks displayed on
           an LCD screen and projected via a mirror attached to the head coil of the fMRI machine
           (each run lasting for 4 minutes) followed by a structural (T1-weighted) scan lasting for
           5 minutes.

      Data Collection Protocol: All recruited participants will be scheduled for 5 visits at the
      TTNI within 48 hours of receipt and subsequent evaluation of the prescreening material for
      inclusion and exclusion criteria. Participants will be reminded of the visits via email /
      telephone (per their stated preference) at both 1 week and again 1 day prior to each visit.
      The visits will be scheduled at least 5 days apart.

        1. First Visit: Prescreening, Consent and Training:

             1. The study will be explained thoroughly to reinforce prior explanations and ensure
                full understanding.

             2. Participants will be screened again to verify the inclusion and exclusion criteria
                by re-administering the screening questionnaire and MRI safety sheet by a member of
                the BMTR lab.

             3. Informed written consent will be obtained.

             4. A participant number will be assigned, that identifies the order of administration
                of the four substances (i.e. theanine, caffeine, TC and placebo) during the
                subsequent visits. This order will be determined using a random number generator.

             5. Each participant will be provided with a solution of 160mg of caffeine dissolved in
                200ml of distilled water in a disposable, clean, opaque, plastic cup to be consumed
                completely within 1 minute, in order to train the participants to consume required
                substances during the subsequent visits and to ensure that the participants can
                tolerate the mildly bitter taste of the substances.

             6. In order to acclimate the participants to the RVRT task they will be performing in
                the MRI scanner during their subsequent visits, each participant will perform a
                training session where they will perform the RVRT task in three 5 min sessions,
                separated by 60 second rest intervals using a laptop computer (under the
                supervision of a graduate / undergraduate research assistants).

             7. Each participant will be reminded of the subsequent visits and the importance of
                adherence to the preparation guidelines.

        2. Preparation and Administration of Substances: L-theanine and caffeine will be purchased
           in purified powder form from a registered supplier. Both substances will be stored in
           air-tight packing prior to preparation for administration according to manufacturer's
           recommendations. All solutions will be prepared for administration maintaining the
           highest possible standards of hygiene. Each solution of L-theanine will be made by
           dissolving 200mg of theanine powder in 200ml of distilled water. Each solution of
           caffeine will be made by dissolving 160mg of caffeine powder. Both L-theanine and
           caffeine powder (200mg and 160mg respectively) will be dissolved in a 200ml aliquot of
           distilled water to form each solution of TC. Two-hundred milliliters of distilled water
           will be used as the placebo. Each solution will be prepared within 4 hours of scheduled
           time of administration and stored in a disposable, clean, opaque, cup with a lid. The
           participants will be instructed to consume the solution completely upon administration.

        3. Preparation of participants for the Second, Third, Fourth and Fifth Visits: All
           recruited participants will be instructed to strictly adhere to the following guidelines
           prior to the 2nd, 3rd, 4th and 5th visits in order to minimize confounding of the
           results.

             1. Avoid consumption of alcohol within 48 hours prior to the test

             2. Avoid smoking 12 hours prior to the test

             3. Sleep for at least 6 hours on the day prior to the test dates

             4. Avoid consumption of tea, coffee or foods / beverages containing caffeine within 12
                hours prior to the test.

        4. Second, Third, Fourth and Fifth Visits: Administration of Substances and MRI Scanning:

             1. Participants will be briefly reminded of the purpose of the study.

             2. Adherence to the preparation guidelines will be assessed. Should a participant
                indicate non-adherence to preparation guidelines they will be discontinued from the
                study.

             3. The solution (containing the appropriate substance / combination of substances) to
                be administered to each participant during the visit will be provided in a
                disposable, clean, cup to be consumed within 1 minute.

             4. A questionnaire regarding the taste and characteristics of the solution will be
                administered.

             5. Each participant will be given a verbal review of the RVRT task and will be allowed
                to practice the RVRT task on a laptop computer for 5 minutes.

             6. Each participant will be allowed to relax, seated in a comfortable chair, until 60
                minutes elapses from the time of administration of the solution (to allow time for
                the actions of L-theanine and caffeine on the brain to reach the maximum levels).

             7. Combined functional and structural MRI scans will be performed while the
                participants engage in the RVRT tasks.

             8. Visual analogue scales (100mm lines with the extremes of the measured parameter
                listed at each end; the participant rates the measured parameter by making a
                vertical mark on the line) will be administered to measure the perceived
                improvement / deterioration of RVRT and perceived improvement / deterioration of
                accuracy in the tasks

             9. At the end of the 5th visit, each participant will be debriefed.

      Analysis: RVRT will be compared across the four conditions (theanine, caffeine, TC and
      placebo) constructing a repeated measures analysis of variance (ANOVA) model using the
      R-statistical software. Subsequently, pair-wise comparisons of RVRT will be performed between
      the four conditions, maintaining the family-wise error rate at 0.05. Following sequence of
      operations will be conducted on the fMRI data using the FMRIB software library (FSL): visual
      examination, distortion correction, motion correction, slice timing correction, spatial
      smoothing and statistical analysis. BOLD responses will be compared across the four
      conditions by constructing ANOVA models at a whole brain level as well as in the regions of
      anterior cingulate cortex and antero-medial prefrontal cortex. Pair-wise comparisons of BOLD
      responses will also be conducted between the conditions. RVRT, omissions and errors will be
      included as covariates in fMRI analysis.
    

Intervention name(s): Theanine; Caffeine; Theanine-Caffeine Combination; Placebo
Intervention type(s): Other; Other; Other; Other
Intervention description(s): Oral administration of 200mg of L-theanine powder dissolved in 200ml of distilled water; Oral administration of 160mg of anhydrous caffeine powder dissolved in 200ml of distilled water; Oral administration of 200mg of L-theanine and 160mg of anhydrous caffeine powder, dissolved in 200ml of distilled water; Oral administration of 200ml of distilled water
Intervention MeSH terms: Caffeine
Intervention model: Crossover Assignment
Masking: Single (Participant)
Keywords: L-theanine; caffeine; selective attention; fMRI; RVRT