Meditation is the attainment of a restful yet fully alert physical and mental state practiced by many as a self-regulatory approach to emotion management, but the psychophysiological properties and personality traits that characterize this meditative state have not been adequately studied. We quantitatively analyzed changes in psychophysiological parameters during Zen meditation in 20 normal adults, and evaluated the results in association with personality traits assessed by Cloninger's Temperament and Character Inventory (TCI). During meditation, increases were observed in fast theta power and slow alpha power on EEG predominantly in the frontal area, whereas an increase in the normalized unit of high-frequency (nuHF) power (as a parasympathetic index) and decreases in the normalized unit of low-frequency (nuLF) power and LF/HF (as sympathetic indices) were observed through analyses of heart rate variability. We analyzed the possible correlations among these changes in terms of the percent change during meditation using the control condition as the baseline. The percent change in slow alpha EEG power in the frontal area, reflecting enhanced internalized attention, was negatively correlated with that in nuLF as well as in LF/HF and was positively correlated with the novelty seeking score (which has been suggested to be associated with dopaminergic activity). The percent change in fast theta power in the frontal area, reflecting enhanced mindfulness, was positively correlated with that in nuHF and also with the harm avoidance score (which has been suggested to be associated with serotonergic activity). These results suggest that internalized attention and mindfulness as two major core factors of behaviors of mind during meditation are characterized by different combinations of psychophysiological properties and personality traits.
Meditation is the mental activity associated with attaining a deeply restful yet fully alert state (Mason et al., 1997). Meditation is practiced by many to facilitate their health and adaptation to medical illness, as a form of systematic training in a self-regulatory approach to stress reduction and emotion management (Bishop, 2002, Kabat-Zinn et al., 1992 and Reibel et al., 2001). In recent years, there have been various studies on the behaviors of the mind during meditation using psychophysiological parameters such as EEG and autonomic nervous activity. During meditation, experienced meditators were reported to demonstrate increased alpha and theta EEG power, and reduced or enhanced autonomic response to external stimuli (Corby et al., 1978, Delmonte, 1984, Travis, 2001 and Woolfolk, 1975).
Mikulas (1990) proposed the usefulness of dividing meditation into four components (form, object, attitude and behaviors of mind). Of these components, form and object vary among meditation techniques. The expressions used for the behaviors of mind induced during meditation also vary, but there are two core components (or some weighted combination of both), i.e., manipulation of one's attentional focus (internalized attention) and maximization of the breadth and clarity of self-awareness (mindfulness) (Mikulas, 1990). In addition, attitude (the mental set in which one approaches meditation) is considered to be an important factor affecting behaviors of mind during meditation (Dunn et al., 1999 and Mikulas, 1990), and its close association with personality traits has been also reported (Bulik et al., 2000 and Helmreich, 1984). Although it is fairly well known that proficient meditation involves the cultivation of internalized attention and/or mindfulness (Mikulas, 1990 and Shapiro, 1982), the psychophysiological properties and personality traits that characterize these two behaviors of mind have not been adequately studied.
In the present study, we used a meditation task called ‘Su-soku’, which is a Zen meditation practice that does not require any special training, as only sustained attention and breath control are needed (Kubota et al., 2001). Normal adults performed the Su-soku task, and we then quantitatively analyzed the changes in psychophysiological parameters (EEG and autonomic nervous activity using heart rate variability (HRV) as an index) during meditation. The obtained results were evaluated in association with induced behaviors of the mind and personality traits.
