The mindful eye: Smooth pursuit and saccadic eye movements in meditators and non-meditators

Keywords

• Mindfulness;
• Meditation;
• Antisaccade;
• Control;
• Attention;
• Intra-individual variability;
• Dispositional mindfulness

1. Introduction

Smooth pursuit and saccadic eye movements are two types of eye movements that both human and non-human primates voluntarily employ to allow the image of an object fall and maintain near to or on the fovea. The function of smooth pursuit eye movements (SPEM) is to keep a retinal image within the area of the fovea during the movement of an object. The initiation as well as the maintenance of accurate SPEM requires attentional control (Hutton & Tegally, 2005). The primary measure of pursuit accuracy is the velocity gain which corresponds to the ratio of smooth pursuit velocity over target or object velocity (100% if SPEM velocity matches the target velocity) (Lencer & Trillenberg, 2008). Other indicators of SPEM efficiency are the frequency of compensatory catch-up and intrusive anticipatory saccades made during the smooth pursuit task.

Saccades refer to the fast eye movements made to the sudden appearance of a visual target. Prosaccades require the participant to make a saccade to a single-target stimulus as soon as it appears. The antisaccade (AS) paradigm, on the other hand, requires the participant to inhibit a reflex-like saccade towards the target, and instead initiate a saccade in the direction opposite to the target (Hutton & Ettinger, 2006). It examines the conflict between a pre-potent stimulus that produces a strong urge to make a saccade to the target, and the overriding goal to look in the opposite direction. Correct AS performance requires accurate perception, ability to transform location information to a mirror image representation, and suppression of a saccade towards the AS stimulus. Performance is assessed as the error rate, spatial accuracy and latency of (anti)saccades (Hutton & Ettinger, 2006). Given their high test-retest reliability (Ettinger et al., 2003) and the ease of administration, SPEM and AS paradigms have been used to assess cognitive functions in a wide variety of contexts (Hutton and Ettinger, 2006 and Lencer and Trillenberg, 2008). However, no published study, to our knowledge, has yet utilised these paradigms to understand the neural and cognitive influence of mindfulness as a trait (‘dispositional’ mindfulness) (Brown & Ryan, 2003), or mindfulness developed through training (‘cultivated’ mindfulness) (Ivanovski & Malhi, 2007).

Mindfulness, a translation of the Pali term sati, is operationalized in modern psychology as a quality of awareness that arises from paying attention to the experience on a moment-by-moment basis without judging, elaborating upon, or fixating on this experience in any way ( Kabat-Zinn, 1990). Its practice typically begins with the mindfulness of bodily sensations to the awareness of feelings and thoughts, progressing to a present-centred awareness without an explicit focus, in most Buddhist traditions as well as formal intervention-style practices such as Mindfulness-Based Stress Reduction (MBSR; Kabat-Zinn, 1990) and Mindfulness-Based Cognitive Therapy (MBCT; Segal, Williams, & Teasdale, 2002). Dispositional mindfulness refers to the naturally occurring tendency to display this non-judgmental present awareness in everyday life and varies amongst individuals (Brown & Ryan, 2003).

There is growing evidence for a positive effect of cultivated mindfulness on a range of cognitive functions (reviews, Chiesa et al., 2011 and Gallant, 2016). Mindfulness practice enhances stability of attention by reducing cortical noise (Lutz et al., 2009) and appears to increase information processing capacity (Slagter et al., 2007) with the cognitive system more rapidly available to process new targets (Slagter, Lutz, Greischar, Nieuwenhuis, & Davidson, 2008). It is reported to positively influence orienting attention (van den Hurk, Giommi, Gielen, Speckens, & Barendregt, 2010), dual attention (Jensen, Vangkilde, Frokjaer, & Hasselbalch, 2012) and performance on a range of tasks requiring attention and/or cognitive flexibility (Hodgins and Adair, 2010, Jha et al., 2007, Jha et al., 2010, Kumari et al., 2015, Moore et al., 2012, Semple, 2010, Tang et al., 2007 and van den Hurk, Janssen, et al., 2010). According to a recent review (Gallant, 2016), mindfulness-led improvements in executive functioning, within Miyake et al.’s model (2000), are more consistently found on specific measures of inhibition (Allen et al., 2012, Heeren et al., 2009, Moore and Malinowski, 2009, Sahdra et al., 2011 and Teper and Inzlicht, 2013), relative to updating (Jha et al., 2010 and Mrazek et al., 2013) and shifting components (Anderson et al., 2007, Chambers et al., 2008, Heeren et al., 2009 and Moynihan et al., 2013).

There are, however, only few data at present examining the association between trait mindfulness, as measured in the general non-meditating population using self-report questionnaires (Brown & Ryan, 2003), and cognitive function, with some studies (Stillman et al., 2014, Stillman et al., 2016 and Whitmarsh et al., 2013) indicating a negative relationship between trait mindfulness and implicit learning, i.e. learning without conscious awareness.