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L I Aftanas

Publications and source records attributed to L I Aftanas.

29 records · Page 2Linked to original sources
PubMed1997

Non-linear analysis of emotion EEG: calculation of Kolmogorov entropy and the principal Lyapunov exponent.

For 76 healthy subjects, two non-linear measures, capturing the dynamical properties of the system orbiting within the attractor (i.e. Kolmogorov entropy, K2 and principal Lyapunov exponent, L1), were calculated from EEG segments, corresponding to different states of brain activity, induced by emotionally valenced (i.e. neutral, affective positive and negative) video stimuli. Significantly elevated values of EEG K2 and L1 in response to both positive and negative film categories as compared to neutral one were evidenced. Relying on the obtained findings, it is suggested that increased cortical dynamics, up to a certain level, are probably necessary for emotion functioning.

Adolescent↗
PubMed1997

Nonlinear forecasting measurements of the human EEG during evoked emotions.

Forecasting ability applied to a single EEG time sequence may quantify loss of memory of past brain states. This fundamental property of complex dynamical systems could prove to be an important measure of current brain states. The present study examined nonlinear forecasting (or nonlinear predictability) estimates of the scalp-recorded EEG in 76 healthy volunteers in response to emotionally charged (negative, positive and control neutral) video-clip stimuli. EEG was recorded from 18 sites (10-20 system). The obtained results indicate that the negative emotional impact led to a more predictable EEG dynamics, compared with neutral or positive emotional video content, and this effect was restricted to the posterior cerebral sites. The studied signatures of EEG dynamics succeed also in specific discrimination between effects of positive and negative film categories: significantly more predictable dynamics over posterior cerebral sites in response to negative film category was accompanied by enhanced predictability in answer to positive film category over frontocortical loci. It is concluded that these findings suggest the association of basic cortical nonlinear mechanisms with the specific physiological processes of emotional processing.

Adolescent↗
PubMed1996

Pre- and post-stimulus processes in affective task and event-related desynchronization (ERD): do they discriminate anxiety coping styles?

The present investigation was designed to study whether pre-stimulus (as measured by EEG power in the time interval before the stimulus presentation) and post-stimulus (as measured by event-related desynchronization (ERD)) processes of alpha components in two frequency bands (8-10 and 10-12 Hz) and their scalp distribution discriminate among anxiety coping styles in an affective task. We investigated this question by using a sample of 30 college students who were split into three groups consisting of 10 low-anxious (LA) and 10 high-anxious (HA) subjects, and 10 repressors (RE). In the present study, positive and negative emotions were operationalized by winning and losing certain amounts of money in gambling situation while measuring ERD to positive and negative feedback stimuli. The main findings of the prestimulus data analyses suggest that the prestimulus level of alpha power is sensitive to the anxiety coping styles. In terms of ERD effects, HA individuals were marked by relatively larger left-hemisphere activation compared to low-anxious subjects and repressors. Further, in contrast to LA and RE, the phenomena observed in our experiment of increased and extended ERD over time in HA in response to negative feedback stimulation implies that threatening information (loss of money) is more persistently activated in subjects with high anxiety. Although preliminary, the reported findings are of potential importance because they could lead to the development of a new psychophysiological measure of relevance to personality.

Adaptation, Psychological↗
PubMed1996

Event-related desynchronization (ERD) patterns to emotion-related feedback stimuli.

Event-related desynchronization (ERD) of alpha components was studied in 14 healthy right handed subjects in an effective task. In the present study positive and negative emotions were operationalized by winning and losing certain amounts of money in a gambling situation while measuring ERD to positive and negative feedback stimuli. All the subjects demonstrated comparable (i.e. statistically not separated) intensities of positive and negative affect of self-report data. The obtained results suggest that ERD can be used as an indicator of localized brain activation in affective tasks. As it was evidenced by ERD analyses, the left and right lobes participated in Valence discrimination. The predicted relative left frontal activation to the positive feedback stimuli and right frontal activation to the negative feedback stimuli was supported. This effect was restricted to the upper (i.e. 10-12 Hz) alpha band. These findings are evidenced in favour of specific role of frontal hemispheric asymmetries in valence discrimination. It is concluded that ERD seems to be able to evidence relatively small differences in emotion processing and appears to be a suitable method with which to study emotion.

Adolescent↗
PubMed1994

Dimensional analysis of human EEG during experimental affective experience.

The present investigation was designed to study whether dimensional complexity of EEG discriminates between internal and external attentional demands during affective experience. In the first task Ss were waiting for a slight electric shock (affective intake condition). In the second task Ss were engaged in the controlled imagery involving the emotional experience 'programmed' during intake task (affective rejection condition). Both affective tasks were compared to the controlled rest condition. The results of imagery trial replicated previous demonstration of the increased dimension of EEG during imagery in comparison to perceptual processing, with differences, confined to frontal and partly to central sites. Affective intake trial in comparison to rest condition was characterized by significantly higher dimensional estimates over the central and more posterior (parietal and occipital) areas.

Adolescent↗
PubMedDate not supplied

[Analysis of elicited EEG synchronization and desynchronization in emotional activation: temporal and topographic characteristics].

Event-related synchronization (ERS) and desynchronization (ERD) in delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma were measured in 20 healthy right-handed subjects in response to IAPS stimuli with low, moderate, and high arousal reactions. The 62-channel EEG was simultaneously recorded while subjects viewed sequentially presented pictures and subjectively rated them after each presentation. The results show that emotionally loaded stimuli induced higher ERS in the delta, theta1, theta2, beta1, beta3, and gamma bands along with combined ERD and ERS effects in alpha2 band. As to hemispheric asymmetries, the effects of emotional arousal were restricted not only to right parietal (theta1 and theta2 ERS, alpha2 ERD) but also to left frontal (theta2 ERS) regions. In terms of affective chronometry, lower theta was the first to catch the affective salience of incoming stimuli (time window 0-600 ms after the stimulus input). For theta2, alpha2, and gamma bands this process was delayed to 600-1000 ms.

Adolescent↗
PubMedDate not supplied

[Characteristics of interhemispheric EEG band power distribution in high anxiety individuals under emotionally neutral and aversive arousal conditions].

The 62-channel EEG was recorded in control (CI, n = 21) and high anxiety (HA, n = 18) individuals under emotionally neutral (eyes closed, eyes open, and neutral videoclip) as well as under emotionally positive and aversive arousal conditions elicited by affective videoclips. In the present study the first three experimental conditions (eyes closed--eyes open--viewing emotionally neutral films) modeled increasing non-emotional arousal. Findings from this continuum show that in the HA individuals the lowest level of tonic arousal (eyes closed) was associated with stronger right-sided parietotemporal theta1 and beta1 activity. Group differences during cortical arousal increased by sensory stimulation (eyes open, neutral clips presentation) were marked only by persisting favored right hemisphere beta1 activity in high anxiety individuals. Under aversive arousal condition, attended by high intensity experience of emotions of anger, fear, disgust and anxiety, the HA subjects selectively desynchronized the right parietotemporal beta1 power which was initially higher in the control conditions. The obtained findings allow to suggest that peculiarities of right-sided parietotemporal EEG theta1 and beta1 activity in HA individuals under studied emotionally neutral and aversive arousal conditions point to overactivated withdrawal system in "checking" and "control" modes.

Anxiety↗
PubMedDate not supplied

[Strengthening interhemispheric interferential inhibition in man with diazepam].

The influence of oral diazepam administration (10 mg) on interhemispheric proactive and retroactive interferential inhibition during detection of test verbal signals was tachistoscopally studied in eight healthy right-handed subjects, in conditions of forward and backward contralateral masking according to the scheme of double blind investigations. Strengthening of effects of forward and backward contralateral masking was revealed which is considered as a testimony to participation of GABA-ergic inhibitory systems in the mechanisms of interhemispheric proactive and retroactive interferential inhibition.

Adult↗