Yoga Practice, Stress and Cognitive Performance
Condition: Attentional Control Switching; Task Switching Between Modalities; Inhibition; Stress; Anxiety
Study type: Interventional

Summary: 
      It has been indicated in recent research that Mindfulness-based interventions may offer
      possibilities of promoting human stress processing and reducing anxiety or depression. They
      also appear to positively influence cognitive performance. One mindfulness-based intervention
      next to a variety of others is yoga, a combination of physical, spiritual, and mental
      practices of Indian origin that arose to alleviate suffering and enhance psychological and
      physical well-being. The goal of the study is to find out how Hatha Yoga, the most common
      form of yoga, consisting of stretches, yoga postures and conscious breathing, affects
      emotional and cognitive processes. An essential part of yoga seems to be the increase of
      self-regulation and consequently the regulation of stress processing and of cognitive
      processes in general. Building on the Attentional Control Theory, it is hypothesized that
      anxiety and stress limit inhibitory function - the ability to block distracting, irrelevant
      information - and also impair the shifting of attention that normally accompanies smooth
      switching between different tasks and their processing requirements. In a randomized
      controlled trial with an experimental and a waiting group, the investigators aim to
      investigate whether active participation in a 60-minute hatha yoga class (intervention) at
      least three times a week for two months leads to less experienced stress and improves
      inhibition and attentional shifting. The intervention period with pre- and postmeasurements
      is expected to start in early January 2022 and end in December 2022. To measure the effect of
      the intervention, the investigators use three experimental test tasks, one each to examine
      inhibition function (here, measured by distractor interference in visual search), switching
      between different tasks or sensory modalities (here, collected by comparing performance after
      passagewise alternation vs. repetition of a sound vs. light discrimination), and alternation
      between different stimulus features (here, determined by comparing passagewise repetition vs.
      alternation of target stimulus color in visual search). In all of the experimental tasks,
      behavioral data (reaction times and error rates) and, in two, additional electrophysiological
      measures (event-related potentials) are collected using EEG. To investigate the role of
      stress the investigators use questionnaires as well as biological stress markers from saliva.
      In addition, participants will receive a link to questionnaires to complete by the start of
      the yoga intervention. On top, trait mindfulness will be examined as a potential mechanism
      underlying the effects of yoga practice on attention and stress. The subjects' trait
      mindfulness will be assessed by questionnaire as well.
    

Detailed description: 
      Main goals of the study and hypotheses

      1) What is the effect of hatha yoga on switching between tasks or sensory modalities (e.g.,
      processing times when switching from tone to light discrimination across tasks compared to
      when switching from tone to light discrimination across tasks) and between features (e.g.,
      processing times when switching from red to green target stimuli across tasks compared to
      when switching from red to green target stimuli across features)? The investigators
      hypothesize that yoga practitioners (intervention group) will show lower switching costs and
      lower error rates than the control group (waiting group). 2) How does hatha yoga affect the
      inhibition function of attention? The investigators expect increased inhibition of salient
      distractors (e.g., green distractors among otherwise red stimuli) during visual search (e.g.,
      for a shape-defined target stimulus in the set of red stimuli per display) in the
      intervention group compared to the control group (indexed by event-related potential PD on
      the distractor) or lower attraction of attention by distractors (indexed by reduced N2pc on
      the distractor). The investigators also expect a lower rate of false alarms and a higher rate
      of hits in visual search performance in the intervention than in the control group. 3) What
      is the effect of hatha yoga on the stress and anxiety levels of the subjects? The
      investigators expect lower cortisol and alpha-amylase levels in the intervention group
      compared to the control group as well as lower levels of subjectively reported stress and
      reported anxiety as indicated by corresponding questionnaire scores in the intervention group
      compared to the control group. 4) What is the effect of Trait Mindfulness on stress
      parameters in the context of yoga intervention? The investigators expect that Trait
      Mindfulness acts as a moderator and that an increase in Trait Mindfulness during the
      intervention also leads to increased stress reduction.

      Power analysis and recruitment strategy

      Based on a power analysis with d = 0.5, 80% power and 5% alpha error, a sample size of 102
      subjects is targeted, increasing to 122 with the expected dropouts of 20%. Potential
      participants will be made aware of the study via social media (Facebook, Instagram) and on
      campus via promotional materials.

      Detailed description of data assessment and study materials

      Interested individuals are first emailed links to screening questionnaires and given
      information about the study design. The investigators screen for mental disorders using
      mini-DIPS, a short version of DIPS (Diagnostic Interview for Mental Disorders). Individuals
      who meet the exclusion criteria will be excluded from the study. For those individuals who
      show interest in participating in the study and who do not meet the exclusion criteria (for
      details see "10. Eligibility"), pretest appointments will be scheduled. At the first pretest
      appointment, the study information will first be discussed together with the participants and
      written informed consent for study participation will then be obtained. The posttest
      appointments will run concurrently, but a consent form does not need to be signed again. In
      addition, the first of the three experimental cognitive tests will take place, during which
      behavioral measures (reaction time, error rate) will be collected in a computer experiment in
      the laboratory of the Faculty of Psychology.

      In addition, at the first pretest/posttest appointment, participants will receive a link to
      the questionnaires that they must complete by the start of the yoga intervention. The
      self-report questionnaires include demographic data (pretest only), Perceived Stress Scale
      (PSS), State-Trait Anxiety Inventory (STAI)-Form Y, and Freiburg Mindfulness Inventory (FMI;
      long version). All mentioned questionnaires (if not specified differently) have to be
      completed in the pretests as well as in the posttest. In addition, the investigators use the
      Patient Health Questionnaire (PHQ) to characterize the sample (one-time at baseline).
      Questions about the feasibility of the intervention and design will be conducted using a
      specially constructed post-monitoring interview. As secondary outcomes, the investigators are
      interested in stress reactivity, which the investigators measure with the Perceived Stress
      Reactivity Scale (PSRS), and fatigue (Multidimensional Fatigue Inventory; MFI), as well as
      the control variables sleep (Pittsburgh Sleep Quality Index; PSQI), resilience (Resilience
      Scale RS-11), social support (Berlin Social Support Scales; BSSS), depressiveness (Beck
      Depression Inventory Revision; BDI- II), and self-compassion (The Self-Compassion Scale;
      SCS). All of these scales are assessed at pretest and at posttest. The investigators
      additionally assess the following data with individual items: Use of hormonal contraceptives,
      ongoing medication use, substance use, use of mind-body techniques, physical activity, BMI.
      In addition, participants receive a list of contact information for appropriate institutions
      to contact in the event of emergencies arising that exceed the project management's areas of
      expertise. At the second pretest (posttest) appointment, the investigators collect behavioral
      data (reaction time and error rate) as well as electrophysiological measures using EEG for
      the two experiments performed. Event-related potentials as well as oscillations are
      evaluated. In addition, independent measurement of cortisol levels and alpha-amylase will be
      performed on three consecutive days before and immediately after the yoga intervention - the
      salivary vessels for this purpose will be distributed at the first pretest appointment and
      the subjects will be instructed accordingly. For this, subjects will independently collect
      five saliva samples per day and date the exact time of collection. They will be instructed to
      store the samples in their own refrigerator or freezer and bring them to the Institute of
      Psychology before the first yoga class. Randomized assignment to experimental or control
      group will then occur only after the respective pretests to control for expectancy effects.
      If the assignment causes individuals to drop out of the study, resulting in a significant
      imbalance in group size, additional subjects will be recruited for the respective group.

      Detailled description of the experiments

      Experiment 1: Inhibition

      In order to find out how the intervention also affects participants' inhibition ability, the
      investigators use an experimental task. The experiment consists of 36 blocks, each containing
      56 trials, and 112 practice sessions. Thus, the experiment lasts approximately one hour with
      breaks. At the beginning of each block, subjects are presented with a target stimulus
      randomly selected from one of nine letters. This target stimulus can be of two different
      sizes (large or small). Should a run contain the target stimulus in the correct size,
      subjects must press the "K" key on their keyboard.

      There are four different conditions: 1) trials that include a target stimulus (576 trials in
      total), 2) trials that include a target stimulus-like distractor, i.e., the same letter in a
      different size, 3) trials involving a salient distractor (a different letter in a color that
      is different from all other stimuli presented in the target stimulus display; 576 trials in
      total), 4) trials that did not meet any of the above conditions (288 trials in total).

      A fixation cross is shown throughout each trial, as is usual for EEG experiments. Stimuli are
      presented for 200 ms, followed by a variable interstimulus interval between 800 and 900 ms.
      The color of the stimuli shown in the target stimulus display is randomly selected in each
      trial from the two possible colors, red and green, with equal probability in order to exclude
      color-specific effects. An exception is the salient distractor in condition 3, which is
      always displayed in the other color. The investigators expect different event-related
      potentials in the different conditions: In conditions 1) and 2) an N2pc, indicative of
      shifting attention, and in condition 3) a Pd, indicative of suppression of the stimulus.

      Experiment 2: Task Switching

      A proven method to assess the functioning of the second function affected by anxiety, the
      shifting function, is to use paradigms that allow for the switching between different tasks
      as well as between different Attention control settings. For the former, the investigators
      would like to use an experimental paradigm in which the investigators measure oscillations in
      the brain by means of EEG, which are called visually evoked steady-state potentials (SSVEP)
      and auditory steady-state responses (ASSR), respectively. They are measured by the
      Presentation of repetitive auditory and visual stimuli. It was found in past studies, that
      the endogenous brain oscillations take over the frequency of presentation of the respective
      modality. Thus, when stimuli in the auditory and visual modalities are presented with
      different frequencies, the investigators obtain millisecond information about which modality
      is currently attended. Our experiment has no distinct trials, instead stimuli are presented
      continuously for 180 seconds before a pause, the length of which can be determined by the
      subjects themselves. The trial consists of 16 blocks and the experiment lasts approximately
      65 minutes with breaks.

      The investigators use a 2-back task for this. Stimuli from the visual and auditory domains
      are presented in different frequencies and the participants have to press a key when stimulus
      n-2 matches stimulus n (with a stimulus gap in between). In the visual domain, a colored
      rectangle is presented in the center of each screen. In the auditory domain, tones with a
      volume of 65 dB are played one after the other.The stimuli are played simultaneously in both
      modalities, a distinct bimodal cue, that is played or presented in one of the modalities
      instead of one of the stimuli, gives an indication to which modality attention should be
      paid. The visual stimuli differ in color, the auditory stimuli vary in pitch. The
      investigators expect faster changes between the tasks in the intervention group, as well as a
      lower error rate.

      Experiment 3: Switching between different attentional control settings

      To investigate the ability to switch between stimulus features, i.e., different attentional
      control settings, the investigators use a contingent capture protocol. Here, the target
      stimuli to be responded differ in their features (such as color), which in turn results in
      the need for switching between the Attentional control settings. In this experiment, there
      are two conditions, each of which is presented in different blocks (A-B-A-B or B-A-B-A,
      balanced across subjects). While in one-color blocks the target stimulus is presented
      exclusively in the color defined at the beginning of the block, in two-color blocks there are
      two target colors, namely red and green, one of which always appears in the target stimulus
      display.

      A pass proceeds as follows: First, against a black background, a fixation display is
      presented for a duration of 1000ms. The subsequent cueing display contains four gray rings
      and is shown for a duration of 50ms. Here, one of the rings takes the target color (or in
      two-color blocks one of the target colors) (matching cue), while the other three remain gray,
      or it takes on another color, namely blue (nonmatching cue). In addition, it is varied
      whether the cue appears at the location of the target stimulus, i.e., is valid, or not, i.e.,
      is invalid. Following an interstimulus interval of 100 ms, the target display now appears for
      150ms. In this target display, all rings get a color, but only one of them is in the target
      color, while two of the three remaining rings are yellow and the remaining ring with equal
      probability is either magenta or cyan. In addition, during the target display, all circles
      contain a T tilted to the left or right. The participants are asked to indicate the
      orientation of the T within the target color circle by pressing the right key (key y for
      left-tilted and m for right-tilted). In the two-color block, the color of the target stimulus
      changes in run n+1 compared to run n with a 50 percent probability, so the investigators get
      equal numbers of trials with target color repeats and target color changes and can derive
      switching costs from this. The investigators can also derive mixing costs from the reaction
      times of the different conditions (one vs. two-color block), indicative of the use of
      different attentional control settings. Before the task, the investigators will instruct
      participants to respond as quickly and accurately as possible. They will also receive written
      feedback on their performance by displaying "Wrong" on the PC screen for incorrect responses
      and "Respond Faster" for 500ms each for response times longer than 1200ms. at There will be a
      total of 4 blocks of 240 trials each with varying condition blocks and 24 practice trials
      each, resulting in an approximate duration of 75 minutes for the experiment, including
      breaks.
    

Intervention name(s): Hatha yoga course
Intervention type(s): Behavioral
Intervention description(s): Participants will join a free hatha yoga course, conducted by a professional yoga teacher, over a time period of eight weeks with a frequency of at least three up to five times a week. The quality of the implementation of the intervention will be checked through post-monitoring by short questionnaires to be filled out by participants.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: A pretest-posttest design is planned, with the pre- as well as the posttests each split into two sessions. Pretests are scheduled in the weeks before the intervention, posttests relatively soon after the intervention. At both data collection times, stress as well as cognitive performance (namely of attention) will be recorded in both groups (experimental group, waiting control group). While the experimental group participates in a 60-minute hatha yoga intervention at least three times a week for 8 weeks, the wait-list control group does not receive the yoga intervention until after the end of data collection.
Masking: None (Open Label)
Primary purpose: Other
Keywords: anxiety; stress; mindfulness; hatha yoga; attentional control settings; attentional control theory; inhibition; shifting; task switching; cognition; attention