Mindfulness meditation is a form of attentional control training by which individuals develop the ability to direct and maintain attention towards the present moment1. It can not only reduce mind-wandering during training, but it can also influence cognitive performance after training, and improve well-being and happiness in daily life2,3,4. Therefore, many mindfulness interventions have been developed as clinical interventions and training programs1,5.

Mindfulness meditation and related interventions consist of focused attention meditation (FAM), which improves concentration abilities, and open monitoring meditation (OMM), which improves the ability to monitor the contents of experience without any reactions or judgments6. Both FAM and OMM aim to keep the practitioner’s attention away from distractors, such as particular bodily sensations, feelings, and thoughts, which evoke mind-wandering. Consistent with this, FAM and OMM can reduce mind-wandering and activity in the default mode network (DMN), a network associated with mind-wandering2,7,8. To achieve this, during FAM, meditators practice sustaining their intentional focused attention on an explicit object. After advancing in FAM, during OMM practitioners reduce intentional focused attention gradually and keep their attention away from distractors without an explicit object6.

It can therefore be asked whether FAM and OMM differ only in the strength of intentional focused attention or whether they differ in their function to keep practitioner’s attention away from distractors. Furthermore, it is not clear whether the ability to keep the practitioner’s attention away from distractors is sustained after practicing FAM and OMM.

Although the neural mechanisms underlying FAM overlap with those underlying attention and have been extensively studied9,10, little is known about the neural mechanisms underlying OMM because the concept of OMM originates from Buddhism and has just begun to be examined within cognitive neuroscience. The non-reactive and non-judgmental monitoring developed by OMM is an important psychological factor in the improvement of well-being and happiness in daily life11. Therefore, it is important to clarify the neural mechanisms underlying OMM and its after-effects.

In FAM, meditators focus their attention on a target object, such as the physical sensations caused by breathing. Having a target object enables meditators to keep their attention away from distractors and to disengage their attention from these distractors more easily6. In functional magnetic resonance imaging (fMRI) studies, FAM has been shown to reduce activity in the anterior medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC)/precuneus2, which are core hubs of the DMN7. In contrast, increased activation has been observed in brain regions involved in the ventral and dorsal attention network12, such as the frontal eye field (FEF), visual cortex, dorsolateral prefrontal cortex (dlPFC), and anterior insula9. More specifically, activity in the anterior insula and dorsal anterior cingulate cortex (ACC) increases at moments when meditators realize their mind is wandering during FAM. Subsequently, the recognition of their mind-wandering and movement of their attention to the target object leads to increased activity in the dlPFC, and caudate, and decreased activity in the mPFC10. That is, FAM enhances intentional focused attention, which is associated with activity in the attention network.

In OMM, meditators keep a non-reactive and non-judgmental awareness of anything that occurs in their experience of the present moment6. While maintaining this awareness, the contents of experience such as bodily sensations, feelings, and thoughts are not distractors but simply contents for observation. However, if meditators react to or judge contents of their experience, as people tend to do automatically and habitually, they become distractors from awareness of the present moment. Compared with FAM, it is more difficult to disengage attention from these distractors during OMM because meditators do not have a target object. Instead, they must simply stop reacting to and judging these distractors. For this purpose, meditators practice OMM to develop a more acute, but less emotionally reactive, awareness of their experiences, including the autobiographical sense of identity that projects back into the past and forward into the future6. Although some studies have shown that OMM also reduces activity in the core hubs of the DMN to the same extent as does FAM2, precise mechanisms underlying these processes are still unclear. From a theoretical perspective, it is conceivable that OMM reduces memory function involvement in ongoing processes. In fact, Taylor et al.13 indicated that OMM reduces activity in the hippocampus and retrosplenial cortex (RSC), which are components of the DMN and are associated with self-reference in the past and future7.

Furthermore, to understand how changes to cognitive functions during FAM and OMM may influence daily life, it is also important to investigate the after-effects of FAM and OMM. Such after-effects form a bridge between states experienced during meditation and traits in daily life. Some studies have indicated that a short mindfulness intervention also reduces mind-wandering4. In this study, we predicted that some alterations in brain activity observed during FAM and OMM would be sustained after meditation. Such brain activity might underlie the effects that FAM and OMM practice have on daily life. Thus, we also investigated the after-effects of brain activity after OMM compared with FAM.

To investigate neural mechanisms underlying OMM and its after-effects compared with FAM, we focused on the attention network and DMN using a functional connectivity analysis, which is a powerful method used to reveal relationships between brain regions. Mindfulness meditation involves a broad range of brain regions, such as the dlPFC, ACC, anterior insula, mPFC, PCC, hippocampus, visual cortex, and striatum9,14,15. In particular, the striatum connects to other cortical regions differentially and forms multiple parallel cortical-striatal loops that can be functionally distinguished, such as attention and memory function loops16,17,18,19,20. Moreover, the striatum plays an important role in reducing habitual behavior and enhancing self-control, including attention control, emotion regulation, and self-awareness during mindfulness meditation15,21,22.

Therefore, to investigate relationships between brain regions underlying self-control and those underlying both attention and memory function, we examined striatal functional connectivity in 17 experienced meditators (mean total practice hours = 920.6) during pre-resting, meditation, and post-resting states comparing OMM with FAM for 6 minutes in each state, using fMRI. In particular, dividing the experiment across two days for FAM and OMM within participants, we were able to allow them 60 minutes for each practice between scans of pre-resting and meditation states. In FAM, participants paid attention to the physical sensation of the breath within a triangle area from the upper lip to nostrils. In contrast, in OMM, participants observed whatever bodily sensation came into their awareness non-reactively and non-judgmentally. In addition, prior to each scanning day, participants had meditated for 30 minutes in their home for seven days following the same instructions as in the experiment.

The main aim of this study was to elucidate the striatal functional connectivity with both attention network regions and DMN regions during OMM by comparing it with functional connectivity during FAM. We hypothesized that OMM would differ from FAM, not only in the intentional focused attention, but also in the involvement of memory function. That is, during FAM, in response to increasing intentional focused attention, the relationship between the striatum and attention network regions would increase. In contrast, if OMM does not require intentional focused attention, during OMM the relationship between the striatum and attention network regions would decrease. Furthermore, in response to decreased involvement of memory function, the relationship between the striatum and DMN regions related to memory function would also decrease. In addition, there would be correlations between such changes during meditation and meditation practice hours. The second aim of this study was to elucidate the after-effects of FAM and OMM. Therefore, we conducted an investigation into after-effects concentrating on functional connectivity that showed changes during FAM or OMM.