Mood
A possible mood enhancing effect of the defined structurally plastinated cortical areas in the present study is worth to give an attention.
In the theory of mind, the DMN activity as a self-awareness state is correlated with the neuronal representation of mind-wandering (Kjaer and Lou,
2000; Kjaer et al.,
2002). This DMN is active at all times except when suppressed by other networks, stimulated by other states, and its activity is correlated with lower levels of Happiness (Killingsworth and Gilbert,
2010; Brewer et al.,
2011). Gusnard and Raichle (
2001) demonstrated that the goal-directed cognitive process can decrease the activity of precuneus, the core hub of the DMN or mind-wandering network of the brain. Therefore, it is theorized that prolonged periods of goal-directed cognitive processes may decrease the mind-wandering activity in the SWD’s brain because the precuneus activity has been decreased. fMRI data results from the Brewer et al. (
2011) study on the DMN of the experienced meditators showed that the DMN main nodes, including medial prefrontal cortex and PCC areas extending to precuneus were relatively deactivated. Further, precuneus and PCC have been observed as thinner and concluded to be so as a response to meditation (Kang et al.,
2013). In line with these results, the structural cortical thickness analysis of the two cohorts in this study showed that the experienced SWDs had bilateral thinner PCC and precuneus zones. It can be therefore be theorized that the prolonged period of decreased activity in the PCC and precuneus may result in the thinner zones in the SWDs. As the DMN activity presented thinner in the SWDs, this is likely related to suppressed mind wandering, and as a consequence, this plasticity may improve the happiness level in SWDs. These results justify further studies to clarify the potential effects of SWDs’s unique meditation on their moods and depression levels.
Behavior
In addition to potential mood enhancing effects by Whirling Meditation as achieved with decreased mind wandering, or by DMN activity as achieved with other types of meditation, decreased activity in the DLPFC may contribute to the behavioral attribute of honesty. As the precuneus stands as a core hub for the DMN, the DLPFC stands as a core hub for the executive network (Beaty et al.,
2015). It has been shown that to achieve creative idea production, there is a coupling of the PCC and precuneus of the DMN with the right DLPFC of the executive network (Beaty et al.,
2015). It has also been shown that increased task complexity or increased rule complexity is accompanied by increased activation in the right DLPFC and precuneus (Jia et al.,
2015). In the case of lying, we need a creative idea production process and to consider long-term benefits. It has been shown that disruption of the right DLPFC leads to a greater selection of both gains and losses that have better immediate but worse long-term alternatives (Essex et al.,
2012). It has also been shown that when the right DLPFC activity was disrupted using TMS, subjects were statistically less inclined to lie about the subject matter tested (Karton and Bachmann,
2011). Regarding the decreased thickness in the right DLPFC in SWDs, it may be theorized that this contributes to improve their behavioral attitude of honesty. It may also be speculated that the decrease in the thickness of fusiform and right DLPFC contributes to decreased discrimination of places and faces, and that such an altered perception of the world and people is also a result of SWDs’s meditations. Further studies are needed to investigate whether the suppression of cortical areas related with discriminational perception leads to less selfish, egocentric behavior and increased level of happiness.
Neuroprotection
The DMN activity is also found to be related to Alzheimer’s disease (Bero et al.,
2011). Bero et al. (
2011) demonstrated that increased amyloid-β deposition overlaps with the DMN, including the core hub, precuneus and PCC regions. This overlapping is attributed to the higher metabolic activity of the DMN. The decreased thicknesses of these regions in SWDs cortex that are shown in the present study may underline a possible whirling meditation protective effect of over Alzheimer disease by its possible effect of decreasing the amyloid-β deposition in these regions because of their decreased activity in SWDs.
Limitations
The current study used a cross-sectional design and it is performed on a small group of SWDs. As a result of the cross-sectional character of the study, the results are correlational and an absolute relationship between the cortical thinning and whirling experience can not be suggested. In addition, it may also be argued that individuals who have such cortical properties are more likely becoming a Sufi whirling Dervish. On the other hand, it is worth to note that there are numerous factors to consider that relate the outcomes of the present study to whirling experience. This is a cross-sectional study in a very unique (and rare) group who had traditional training for whirling (approximately 1 year in most of the cases) and each of them reported that they were falling down when they try to whirl in the first months of the whirling training sessions. This indicates that they did not have a unique previous ability that was superior to the predisposition of the control group. After the long-term training, they gained an ability to whirl without vertigo. The present cross-sectional study focused on experienced Sufis that passed through the same traditional whirling training that enabled them to whirl for an hour without falling. In this context, the detected structural differences are more likely to be specific to motion perception and body perception networks. As the analyses were performed without visual input, the outcomes of these areas are free of bias. Analyses within the article were almost not separated but discussed in the context of relevant networks. The structural cortical plasticity that was demonstrated in SWDs were distributed over the body/motion perception areas, therefore the discussion was focused on the possible relationships of the structural plasticity of the body/motion perception areas and their potential role to alter vertigo perception. In sum, we only explained the results on the basis of the previous work which was the most fitting way for the data obtained in this cross-sectional article. Longitudinal studies are needed to clarify the role of these areas in vertigo perception.
The outcomes of this cross-sectional study in a rare and unique group (whirling Sufi dervishes) warrants cortical zones which may have significant roles to alter vertigo/dizziness and address those areas for future studies. In conclusion, this is the first report that demonstrates correlations of the structural cortical plasticity and the prolonged period of vestibular system stimulation in humans.
Author Contributions
YOC designed, performed the study, analyzed the data and wrote the manuscript and made critical review of the manuscript. GE performed the study, collected data, contributed analytical tool, made critical review of the manuscript. AH analyzed and interpreted data, contributed analytical tool, performed statistics and made critical review of the manuscript. SÇ contributed analytical tool, collected data, wrote manuscript and made critical review of the manuscript.
Funding
The study is funded by the Start-up fund of YOC, School of Biomedical Sciences,University of Otago.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. AH is employed by Brain Innovation at Biopartners Center, Maastricht, Netherlands, as a member of the Brain Voyager software support team. He assisted in preparing the data with the new version of BrainVoyager. AH’s employment by Brain Innovation does not alter the authors’ adherence to all the Frontiers Journals policies on sharing data and materials.