Impact of regular meditation practice on EEG activity at rest and during evoked negative emotions.

The main objective of the present investigation was to examine how long-term meditation practice is manifested in EEG activity under conditions of non-emotional arousal (eyes-closed and eyes-open periods, viewing emotionally neutral movie clip) and while experiencing experimentally induced negative emotions (viewing aversive movie clip). The 62-channel EEG was recorded in age-matched control individuals (n=25) and Sahaja Yoga meditators (SYM, n=25). Findings from the non-emotional continuum show that at the lowest level of arousal (eyes closed) SYM manifested larger power values in theta-1 (4-6 Hz), theta-2 (6-8 Hz) and alpha-1 (8-10 Hz) frequency bands. Although increasing arousal desynchronized activity in these bands in both groups, the theta-2 and alpha-1 power in the eyes-open period and alpha-1 power while viewing the neutral clip remained still higher in the SYM. During eyes-closed and eyes-open periods the controls were marked by larger right than left hemisphere power, indexing relatively more active left hemisphere parieto-temporal cortex whereas meditators manifested no hemisphere asymmetry. When contrasted with the neutral, the aversive movie clip yielded significant alpha desynchronization in both groups, reflecting arousing nature of emotional induction. In the control group along with alpha desynchronization affective movie clip synchronized gamma power over anterior cortical sites. This was not seen in the SYM. Overall, the presented report emphasizes that the revealed changes in the electrical brain activity associated with regular meditation practice are dynamical by nature and depend on arousal level. The EEG power findings also provide the first empirical proof of a theoretical assumption that meditators have better capabilities to moderate intensity of emotional arousal.

Trait anxiety impact on posterior activation asymmetries at rest and during evoked negative emotions: EEG investigation.

The main objective of the present investigation was to examine how high trait anxiety would influence cortical EEG asymmetries under non-emotional conditions and while experiencing negative emotions. The 62-channel EEG was recorded in control (n=21) and high anxiety (HA, n=18) non-patient individuals. Results showed that in HA subjects, the lowest level of arousal (eyes closed) was associated with stronger right-sided parieto-temporal theta-1 (4-6 Hz) and beta-1 (12-18 Hz) activity, whereas increased non-emotional arousal (eyes open, viewing neutral movie clip) was marked by persisting favored right hemisphere beta-1 activity. In turn, viewing aversive movie clip by the HA group led to significant lateralized decrease of the right parieto-temporal beta-1 power, which was initially higher in the emotionally neutral conditions. The EEG data suggests that asymmetrical parieto-temporal theta-1 and beta-1 EEG activity might be better interpreted in terms of Gray's BAS and BIS theory.

Associations of alexithymia with anterior and posterior activation asymmetries during evoked emotions: EEG evidence of right hemisphere "electrocortical effort".

The objective of the study was to examine alexithymia influence on regional cortical activity in nonpatient individuals during evoked emotions. The 62-channels EEG was recorded in non-alexithymic (n = 27) and alexithymic (n = 17) participants viewing emotional film clips. Effects of alexithymia were found in the upper theta, low and upper alpha frequency bands; in all the bands the alexithymics exhibited greater reactivity of the right hemisphere, suggesting enhanced avoidance motivational tendencies, negative affect, and autonomic arousal. Such a right-hemispheric "electrocortical effort" in alexithymia could reflect difficulties in symbolization of emotion resulting from impaired right-hemispheric analogical and global nonverbal emotional representation.

Trait anxiety impact on the EEG theta band power changes during appraisal of threatening and pleasant visual stimuli.

The main objective of the present investigation was to examine whether trait anxiety construct would influence EEG event-related synchronization (ERS) of the theta power during viewing of visual threatening stimuli. The 62-channel EEG was recorded while low (LA, n= 18) and high (HA, n= 18) trait-anxious subjects viewed sequentially presented neutral, threatening and pleasant pictures. Between-group differences, related to stimulus emotionality, were linked to the test period of 0-1000 ms after stimulus onset. In the low theta (4-6 Hz) at prefrontal sites HA exhibited deficient ERS in response to both threatening and pleasant stimuli in the right hemisphere, whereas LA yielded larger right than left hemisphere ERS in response to all the three stimulus categories. In the upper theta (6-8 Hz) group differences were associated with posterior cortical regions: HA exhibited the largest ERS to threatening and the lowest to pleasant stimuli, whereas LA prompted the largest ERS to pleasant and the lowest to neutral pictures. It is suggested that low theta right prefrontal hypoactivation favoring left hemispheric (i.e. more analytical) activity along with higher upper theta ERS of posterior cortical regions (i.e. enhanced higher order visual processing) to threatening stimuli could form the basis for neuropsychologically observed general bias towards threatening information in HA.

Time-dependent cortical asymmetries induced by emotional arousal: EEG analysis of event-related synchronization and desynchronization in individually defined frequency bands.

Event-related desynchronization (ERD) and synchronization (ERS) in the individually defined theta, alpha-1, alpha-2 and alpha-3 frequency bands were measured in 20 healthy subjects in response to International Affective Picture System (IAPS) stimuli with low, moderate and high arousal (LA, MA and HA) content. The 62-channel EEG, skin conductance response (SCR) and heart rate (HR) were simultaneously recorded while subjects viewed sequentially presented pictures and subjectively rated them after each presentation. In the theta band, both MA and HA vs. LA stimuli induced larger synchronization over the left anterior and bilaterally over posterior cortical leads. However, rather unexpectedly, both MA and HA vs. LA stimuli yielded larger alpha-1 synchronization, predominantly over occipital leads. In both theta and alpha-1 bands, affectively salient stimuli prompted larger ERS against the background of the overall dominance in power synchronization of posterior regions of the right hemisphere, irrespective of stimulus category. Finally, in the alpha-3 band, HA stimuli induce a lateralized time-dependent power increase over anterior leads of the left hemisphere. The hemispheric asymmetries revealed point to recruitment of not only posterior regions of the right hemisphere (theta and alpha-1 bands), but also of anterior regions of the left hemisphere (theta and alpha-3 bands) in affect analysis beyond valence dimension. In terms of affective chronometry, the significant arousalxtime interactions clearly indicate that in the theta frequency band discrimination of affective stimuli has already started at 200 ms post-stimulus, whereas in the alpha-1 and alpha-3 bands this process is delayed by up to 800-1200 ms.