Un trabajo de conocimiento con sentido ético

Mindfulness Meditation (MM) and Meditation Breath Attention Scores (MBAS)

Participants in the MM group were introduced to a simple mindful breathing meditation administered using standard published procedures (Frewen et al., 2008, 2011, 2014) by M.Sc. student researchers Theodore Chow and Tanaz Javan as supervised by Dr. Paul Frewen. Participants were instructed to focus their attention toward the sensation of their breathing at their nostrils. They were asked to refrain from manipulating their breathing in any form, and instead to allow their natural breathing rhythm to occur. They were instructed that, whenever they became aware that their attention had wandered from a focus on breathing sensation they should simply redirect their attention back to the sensation of their breathing. In addition to focusing their attention toward their breath, participants were instructed to observe any

distracting thoughts, feelings, or sensations without judging, evaluating, or elaborating on them. This meditation is in line with recent psychological conceptualizations of MM that emphasize the development of attentional abilities combined with a specific, non-judgmental attitude toward the different mental experiences that may arise during MM (Slagter, H.A., et al, 2011; Lutz, et al., 2008).

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Participants were given 3-minutes prior to the start of the meditation to adjust to the environmental setting. MM was practiced while participants were seated comfortably on a chair, with arms rested on their lap. Subsequently, a 15-minute timed MM began. Three consecutive meditation bells were sounded to mark the beginning and ending of the MM. Additionally, a single meditation bell was sounded approximately at 3-minute intervals throughout the session (5 bells in total). During these interval bells, participants were cued to self-report whether at these moments their attention was directed towards their breathing (intended focus), scored 1, or if instead at these moments they were presently distracted by other thoughts, feelings, sensations, or other experiences (i.e., mind-wandering), scored 0. This was done by placing a standard QWERTY keyboard on their lap, where participants pressed the keys “l” or “s” if their attention was on their breath or otherwise, respectively, whilst keeping their eyes closed. This data collection procedure provides the Meditation Breath Attention Score (MBAS) self-report measure, previously used to self-report relative concentration levels (versus proneness to distractibility or mind wandering) during the practice of MM (Frewen et al., 2008, 2011, 2014). In other words, the MBAS was originally designed to operationalize a performance variable relating to MM practice indexing the extent of concentration or attentional control present during the meditation, with the MBAS assessing the participants’ ability to sustain their attention toward their intended focus (i.e. breathing) during the MM practice, and accordingly their ability to disengage from mind wandering. Calculation of the MBAS involved simply summing the

number of times out of five that participants reported that they were attending toward their breath during each of the five meditation bells. In support for the construct validity of MBAS, previous studies identified positive correlations between MBAS and responses to the Five Factor

Mindfulness Questionnaire subscale “Acting with Awareness,” as well as self-report measures relevant to the experience of mindfulness (Frewen et al., 2008, 2010, 2014). MBAS were also found to improve with repeated practice of MM in a previous study (Frewen et al., 2014).

Previous undergraduate samples have achieved a mean MBAS score of 2.36 (SD = 1.24, Frewen et al., 2008), and typically ranged between 0 and 3 (M = 1.74, SD = 0.88, Frewen et al., 2011).

EEG-Alpha Neurofeedback (NFB)

Participants in the NFB group were trained to enhance their EEG-alpha amplitude at their scalp Pz site (midline parietal cortex), where the EEG-alpha rhythm is typically maximal

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(Ergenoglu et al. 2004). To accomplish this, a single electrode was placed at the Pz site according to the 10-20 internationally standardized system for electrode placement. Prior to electrode placement, skin was prepared with NuPrep (Weaver and Company, US), a mildly abrasive skin cleaner to help improve impedance and conductance of electrodes. Electrodes were then affixed with adhesive conductive paste (Ten20, Weaver and Company, US). The electrode was connected to a Spectrum4 amplifier (J&J Engineering, United States) interfacing with EEGer 4.3 neurofeedback software (EEG Spectrum Systems, CA). Separate ground and

reference electrodes were placed on the right and left earlobes, respectively. Once all electrodes were connected, impedances were checked to be at or below 5kΩ measured at the Pz and reference electrode sites. Each session began with a 3-minute adjustment period where

participants were allowed to become comfortable in the laboratory setting. This was followed by 15-minutes of continuous neurofeedback, where participants were asked to close their eyes for the duration of the training. For the purpose of NFB training specifically of the EEG-alpha rhythm, the raw EEG signal was band-pass filtered using the infinite impulse response function to extract the alpha (8-12Hz) amplitude with an epoch size of 0.5 seconds.

The protocol was such that participants were guided toward continually increasing or enhancing their absolute EEG-alpha amplitude beyond a moving threshold. The amplitude threshold for reward was calculated based on the moving average amplitude measured every 0.5 seconds. Thresholds in NFB are typically set in such a way that the participant achieves a certain level of success that is neither too high nor too low (Demos, 2005). As such, the initial threshold was set such that their EEG-alpha amplitude would temporarily exceed the moving threshold at random 65% of the time above the initial 1-minute average; by contrast, participants would fail to receive feedback 35% of the time. The rate of reward achieved by each participant was constantly monitored such that when participants achieved disproportionately larger (>90%) or lower (>30%) reward rates, the standard 65% reward ratio was re-calculated and applied. This ensured that participants were provided a relatively constant level of guidance (feedback) toward the target of increasing-enhancing their alpha amplitude relative to ongoing success toward that goal. Positive feedback was provided as a low frequency auditory tone; being that the sounding of the tone itself is not intrinsically rewarding, it must be assumed that participants are motivated by their own self-efficacy and/or the intrinsically rewarding properties of the targeted

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with their eyes closed, were not given explicit strategies for producing the tones, but were instead asked to focus their attention continuously toward the tones for guidance.

Sham Neurofeedback (NFB)

All set-up and training procedures applied to the sham NFB group were identical to those for the real EEG-Alpha NFB group. Instructions were similarly identical and all participants completed 15-minutes of sham NFB in which participants similarly attempted to produce the audio tones. However, whereas the real NFB group heard auditory feedback that validly reflected their own brain activity, the sham group heard a pre-recorded session that involved the exact same tones the real NFB group was exposed to (Raymond, et al 2005). Pre-recorded sessions were created by placing a digital voice recorder beside the computer speaker during Alpha-NFB training sessions, recording their auditory feedback tones. The pre-recorded session was then played back to Sham-NFB participants using Windows Media Player (Microsoft, USA). In this way, the feedback given to the sham group bore no relation to the participants’ actual own brain activity, but still mimicked the feedback that would typically occur during a true NFB session.