**2.2 Meditation**

Meditators have been found to score higher on trait absorption than controls [95, 110]. In addition, increased theta and alpha power, reflecting activity of multifunctional neuronal networks and differentially associated with orienting, attention, memory, affective, and cognitive processing, is evident in meditators [80]. Altered theta and alpha activity has consistently been reported following meditation [111]. In fact, numerous studies conducted with Western meditators, usually having less than 10 years' experience, have reported increased power and coherence in the alpha and theta frequency bands during meditation practice [39, 111, 112]. Increased gamma power has also been reported in studies with advanced meditative practitioners [38, 73, 113, 114].

Consistent with previous meditation research (for review see [115]), also Berman and Stevens [116] found increased delta (0–4 Hz), theta, and alpha activity during meditation. When differentiating between general meditation and nondual states (in which the participant transcends the separation between self and other), the opposite trend was observed for gamma, which was higher during the meditation sessions in entirely compared to the nondual state [116]. Similarly, Berkovich-Ohana et al. [73], who examined three levels of mindfulness expertise and controls, found that mindfulness practitioners generally exhibited reduced resting-state frontal low gamma power as compared to controls, as well as decreased resting-state gamma functional connectivity representing DMN deactivation in the long-term practitioners, suggesting a trait/long-lasting effect of reduced mind-wandering and self-related processing [73, 117]. In addition, creativity, as measured by ideational fluency and flexibility, which were higher in the long-term practitioners than

**79**

*Inner Navigation and Theta Activity: From Movement to Cognition and Hypnosis…*

**2.3 OVO Whole-Body Perceptual Deprivation (OVO-WBPD)**

short-term practitioners and control participants, was negatively correlated with gamma interhemispheric functional connectivity [118]. Thus, one should keep in mind that different mediation techniques can produce different electrophysiological results, depending among others on the depth of the experience and the experimen-

As we will see in the current section, studies examining perceptual movement, where movement is absent and stillness is the main feature, were also found to be related mostly on delta waves. While delta has historically been associated with sleep and pathological processes, it has recently been found to be related to both autonomic and metabolic processes, suggesting that it is involved in integration of cerebral activity with homeostatic processes, as well as in motivation and reward, as delta also increases during hunger, sexual arousal, and sustained pain [119]. Delta activity is further related to attention, salience detection, and subliminal perception, consistent with meditative states and absorption [116, 119, 120], such as in the

In-line with previous research linking delta waves in meditative states [125], a recent study examined the effects of the OVO Whole-Body Perceptual Deprivation (OVO-WBPD) chamber effects on absorption in experienced meditators. The OVO, an altered sensory environment, is in the form of a human-sized egg ("uovo" means egg in Italian), within which the subject cannot easily perceive spatial coordinates. Based on the Sphere Model of Consciousness, the OVO-WBPD was specifically built with the aim of facilitating an immersive experience and an increased state of *presence* [11]. Ben-Soussan et al. [120], who studied participants who were instructed to "rest as best as they can" in the OVO chamber, found an increased state of absorption, which was accompanied by enhanced delta and lower theta activity, as well as beta (13–20 Hz) activity, peaking in the insula. These results may suggest an enhanced effort to sensory-integrate intero-

In addition to the insula [120], theta was further linked to another main area of the salience network, namely, the anterior cingulate [126–131]. While DMN activity is negatively correlated with both hypnosis and theta activity [129–131], the salience network is thought to support the detection of subjectively important events and the mobilization of attentional and working memory resources in the service of

<sup>3</sup> Yoga Nidra is defined as a "state in which an individual demonstrates all the symptoms of deep, non-REM sleep, including delta brain waves, while simultaneously remaining fully conscious [121]. In addition, it is important to note that while meditation spindles have similar amplitudes to those in sleep, all other parameters are significantly different, with more-experienced subjects displaying high-voltage slow waves reminiscent, but significantly different, to the slow waves of deeper stages of non-REM sleep [122]. In addition, they also differ from slow delta activity in anesthesia which is notably less rhythmic and coherent [122]. Most importantly, the main regions of interest are notably different to those in sleep [122, 123]. More specifically, the significant presence of limbic sources in meditation support the hypothesis of the effects of meditation on memory and spatial and temporal orientation, and consequently to the ventral and dorsal streams of attention and feeling- and salience-based, respectively [122]. The electrophysiological change induced by these type of training, together with the ability to remain consciously aware while producing delta waves, is believed to be associated with attaining a highly stabilized state of higher consciousness [121, 124] and the integration of transcendental experiences in

*DOI: http://dx.doi.org/10.5772/intechopen.92755*

tal design [116].

case of Yoga Nidra [121]<sup>3</sup>

ceptive signals.

goal-directed behavior [132–134].

both waking, dreaming, and sleeping [125].

.

*Inner Navigation and Theta Activity: From Movement to Cognition and Hypnosis… DOI: http://dx.doi.org/10.5772/intechopen.92755*

short-term practitioners and control participants, was negatively correlated with gamma interhemispheric functional connectivity [118]. Thus, one should keep in mind that different mediation techniques can produce different electrophysiological results, depending among others on the depth of the experience and the experimental design [116].
