Biomedical subjects

N V Reva

Publications and source records attributed to N V Reva.

12 recordsLinked to original sources

PubMed2006

Neurophysiological correlates of induced discrete emotions in humans: an individually oriented analysis.

Studies on 30 right-handed subjects addressed EEG characteristics (62 channels) in conditions of laboratory simulation of induced emotions of happiness, joy, anger, disgust, fear/anxiety, and sadness. Induced emotions were found to produce, along with common features, individual patterns in the distribution of amplitude-frequency EEG characteristics. Induced positive and negative discrete emotions were characterized by interhemisphere activatory asymmetry in the theta-2 (4-6 Hz), alpha-2 (10-12 Hz), and beta-1 (12-18 Hz) ranges. Experience of the emotions of joy, anger, and disgust occurred on the background of asymmetrical increases in activity in the anterior cortex of the left hemisphere in the theta-2 range, suggesting a leading role for the activity of these areas in realizing the cognitive components of emotional reacting. In addition, some high-ergicity negative emotions evoked combined alpha-2 and beta-1 desynchronization (disgust) or beta-1 desynchronization (fear/anxiety) in the right parietal-temporal cortex, suggesting its involvement in the mechanisms of non-specific emotional activation. These data provide evidence that each of these emotions is characterized by its own individual pattern in the distribution of the amplitude-frequency characteristics of the EEG and, on the other hand, that series of ranges and cortical areas show similar but different (in terms of intensity) effects in response to emotional activation for emotions of different flavor.

Adolescent↗

PubMed2005

Analysis of evoked EEG synchronization and desynchronization during perception of emotiogenic stimuli: association with autonomic activation processes.

The cortical apparatus involved in performing autonomic responses in conditions of emotional activation has received little study. The aim of the present work was to assess the dynamics of evoked EEG synchronization and desynchronization at different frequency ranges during the perception of emotiogenic visual stimuli depending on the extent of accompanying autonomic activation as measured by skin galvanic responses. Studies were performed on 33 students (all right-handed) aged 18-28 years. Difference between subjects with weak (SGR(-)) and strong (SGR(+)) skin galvanic responses were seen only in the theta1 range (4-6 Hz). At the stage at which emotiogenic information was perceived (the first second after the start of stimulus presentation), both groups showed similar dynamics of increases in evoked synchronization in the parietal-temporal-occipital areas of the cortex, with greater involvement of the right hemisphere. From the second second to the end of presentation (2-6 sec), emotiogenic signals gave significantly greater levels of evoked synchronization in these cortical areas as compared with neutral stimuli, and only in the SGR(+) group. These data provide evidence for the involvement of the posterior areas of the cortex of the right hemisphere in the mechanisms of motivational attention and sympathetic activation.

Adolescent↗

PubMed2004

The coincidence between late non-phase-locked gamma synchronization response and saccadic eye movements.

The event-related response in the gamma (30-45 Hz) frequency band was studied in healthy subjects (n=45) viewing sequentially presented pictures from the International Affective Picture System. The distinct non-phase-locked gamma response was obtained in characteristic time window (200-400 ms) with clear-cut centro-parietal location. The strong coincidence between induced gamma oscillations and saccadic eye movements was revealed. We suggest that saccade-related gamma increase is another manifestation of the phenomenon known as presaccadic spike potential, which is commonly registered over parietal scalp leads at 10-20 ms prior to saccade onset. It is hypothesized that late non-phase-locked gamma synchronization mainly reflects activity of a system responsible for attentional tuning and motor planning/execution of saccadic eye movements.

Action Potentials↗

PubMed2004

Analysis of evoked EEG synchronization and desynchronization in conditions of emotional activation in humans: temporal and topographic characteristics.

Studies in 20 healthy right-handed subjects analyzed evoked EEG synchronization and desynchronization in the delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma ranges in response to sequential presentation of stimuli from the International Affective Picture System (IAPS) with low, medium, and high emotional activation impact. Each signal presentation was accompanied by subjective scaling of the extent of its emotional impact. EEG traces were recorded in 62 channels as signals were presented. These experiments showed that the degree of emotional impact of the signal was significantly associated with increases in evoked synchronization in the delta, theta1, theta2, beta1, beta3, and gamma ranges and with the effects of combined changes in evoked synchronization and desynchronization in the alpha2 frequency range. The interhemisphere distribution of evoked changes in power provided evidence that not only the posterior areas of the right hemisphere were involved in analyzing the emotional significance of images, as indicated by changes in evoked theta1 and theta2 synchronization and alpha2 desynchronization, but also the anterior areas of the left hemisphere, as indicated by changes in evoked theta2 synchronization. From the standpoint of affective chronometry, the earliest discrimination of the emotional content of stimuli, regardless of the sign of the emotion, occurred in the lower theta range and was seen at 0-600 msec after the start of stimulus presentation. This process was delayed 600-1000 msec in the theta2, alpha2, and gamma ranges.

Adolescent↗

PubMed2004

[Event-related synchronization and desynchronization of EEG during perception of emotional stimuli: association with autonomous nervous system activity].

Up to now, mechanisms of neurovisceral integration are not clear. The main objective of the present investigation consisted in studying cortical concomitants of sympathetic activity during emotional perception. The 62-channel EEG and skin conductance response (SCR) were recorded while right-handed healthy participants (n-33) viewed sequentially presented neutral, pleasant, and unpleasant pictures. The event-related synchronization (ERS) and desynchronization were measured in different frequency bands. Relying on median split of SCR amplitudes elicited by the presented stimuli the participants were segregated into groups with low (SCR-) and high (SCR+) autonomous activity. In was revealed that group differences were associated with power changes in the low (4-6 Hz) theta band only. For both groups in the early test period (up to 1 s after stimulus onset), emotional vs. neutral stimuli induced larger theta-ERS over posterior cortical regions with greater impact on the right parieto-temporo-occipital regions. At the later phases (2-6 s after stimulus onset), only the SCR group retained emotion-related greater right hemisphere synchronization. It is concluded that the right parieto-temporo-occipital cortex mediates mechanisms of motivated attention and sympathetic activation.

Adolescent↗

PubMed2004

[Neurophysiological correlates of induced discrete emotions in humans: an individual analysis].

The present study addressed EEG pattering during experimentally manipulated emotion. Film clips previously shown to induce happiness,joy, anger, disgust, fear/anxiety, sadness, as well as neutral control films, were presented to 30 university students while a 62-channel EEG was recorded, and a self-reported effect was described. Analyses revealed both emotion-specific and emotion-unspecific EEG pattering for the emotions under study. Induced positive and negative emotions were accompanied by hemispheric activation asymmetries in theta-2, alpha-2, and beta-1 EEG frequency bands. Emotions of joy and disgust induced lateralized a theta-2 power increase in anterior-temporal and frontal regions of the left hemisphere reflecting involvement of cognitive mechanisms in the emotional processing. Negative emotions of disgust and fear/anxiety were characterized by alpha-2 and beta-1 desynchronization of the right temporal-parietal cortex, suggesting its involvement in modulation of the emotion-related arousal.

Cerebral Cortex↗

PubMed2003

Disruption of early event-related theta synchronization of human EEG in alexithymics viewing affective pictures.

The 62-channel EEG was recorded while control non-alexithymic (n=21) and alexithymic (n=20) participants viewed sequentially presented neutral, pleasant and unpleasant pictures and subjectively rated them after each presentation. The event-related synchronization (ERS) to these stimuli was assessed in the theta-1 (4-6 Hz) and theta-2 (6-8 Hz) frequency bands. The obtained findings indicate that alexithymia influences perception of only emotional stimuli. Over anterior cortical regions alexithymia vs. control individuals in response to both pleasant and unpleasant stimuli manifested decreased left hemisphere ERS in the early test period of 0-200 ms along with enhanced ERS in response to negative vs. positive and neutral stimuli in the right hemisphere at 200-600 ms after stimulus onset. The findings provide the first EEG evidence that alexithymia construct, associated with a cognitive deficit in initial evaluation of emotion, is indexed by disrupted early frontal synchronization in the upper theta band that can be best interpreted to reflect disregulation during appraisal of emotional stimuli.

Affective Symptoms↗

PubMed2003

[Effect of alexithymia on the event-related theta-synchronization of human EEG during reception of emotional visual stimuli].

The 62-channel EEG was recorded while control non-alexithymic (n = 21) and alexithymic (n = 20) participants viewed sequentially presented neutral, pleasant and unpleasant pictures and subjectively rated them after each presentation. The event-related synchronization (ERS) to these stimuli was assessed in the theta-1 (4-6 Hr) and theta-2 (6-8 Hz) frequency bands. The obtained findings indicate that alexithymia influences perception of only emotional stimuli. In the upper theta over anterior cortical regions alexithymia vs control individuals in response to both pleasant and unpleasant stimuli manifested decreased left hemisphere ERS in the early test period of 0-200 ms along with enhanced ERS in response to negative vs positive and neutral stimuli in the right hemisphere at 200-600 ms after stimulus onset. The findings provide the first EEG evidence that alexithymia construct, associated with a cognitive deficit in initial evaluation of emotion, is indexed by disrupted early frontal synchronization in the upper theta band that can be best interpreted to reflect disregulation during appraisal of emotional stimuli.

Affective Symptoms↗

PubMed2002

[Reflection of the emotion manifestation in effects of evoked EEG synchronization and desynchronization].

Event-related desynchronization (ERD) and synchronization (ERS) in response to neutral, positive and negative emotional IAPS stimuli were measured in narrow theta, alpha-1, alpha-2 and alpha-3 frequency bands in 22 healthy Ss. A high resolution 62-channel EEG was recorded while subjects viewed a sequence of pictures. The effects of valence discrimination related to hemispheric asymmetries are associated with increased theta and alpha-3 synchronization. Theta ERS revealed a significant valence by hemisphere interaction for anterior temporal leads in the time window of 100-700 ms after stimulus onset indicating a relatively greater right hemisphere ERS for negative and a left hemisphere ERS for positive stimuli in comparison to neutral those. In the alpha-3 band, negative stimuli induced a left hemisphere ERS increase (F7 site) in the time window of 800-1200 ms not observed for neutral and positive stimuli. The results obtained along with the earlier observations on EEG correlates of affective processing challenge the notion that effective anterior hemispheric asymmetries are reflected mainly in the wide alpha frequency band.

Adolescent↗

PubMed2001

Affective picture processing: event-related synchronization within individually defined human theta band is modulated by valence dimension.

Event-related desynchronization (ERD) and synchronization (ERS) in the theta frequency band was measured while subjects viewed stimuli with differing emotional content (from the International Affective Picture System). A significant valence by hemisphere interaction emerged only in the anterior temporal regions, showing relatively greater right hemisphere ERS for negative and left hemisphere ERS for positive stimuli. In turn, in the posterior brain regions affectively valenced vs neutral stimuli prompted larger extent of ERS against the background of the overall right hemisphere dominance in theta synchronization. The findings document that valence discrimination is associated with the early (200-500 ms poststimulus) time-locked synchronized theta activity as well as hemispheric asymmetries in anterior-posterior direction.

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

[Event-related synchronization and desynchronization of EEG during appraisal of threatening and pleasant visual stimuli in high anxious subjects].

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 IAPS stimuli. Event-related desynchronization (ERD) and synchronization (ERS) were studied in the delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma frequency bands. Between-group differences, related to stimulus emotionality, were linked to theta1 and theta2 bands. In the low theta at prefrontal sites in the test period of 100-700 ms after stimulus onset HA exhibited relative predominance of the left hemisphere in response to both threatening and pleasant stimuli, whereas LA yielded larger right than left hemisphere activity in response to all the three stimulus categories. In the upper theta band between group differences were associated with posterior cortical regions and the test period of 0-1000 ms after stimulus onset: HA exhibited the largest ERS to threatening, whereas LA prompted the largest ERS to pleasant stimuli. Finally, according to the ERD data, in the alpha1 band HA participants in comparison with LA revealed enhanced left hemisphere activation in response to all the stimulus categories. It is suggested that as it is indexed by theta-ERS relative predominance of the left hemisphere at prefrontal sites along with the largest bilateral activity of posterior cortical regions (i.e., enhanced higher order visual processing) to threatening stimuli could form the basis for general bias towards threatening information in HA at the very early stages of emotional processing.

Adolescent↗