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Neural correlates of body awareness and phantom sensation
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Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205
EEGs (Cz) were measured while volunteers (n = 18) received electrical stimuli, duration 1 ms, on the phalange of the middle finger. Each volunteer received 9 conditions, each consisting of 3 blocks of 10 stimuli with a pause of 15 s between each block. The pain was rated on the VAS after each block. The conditions differed in interstimulus interval (0.5; 1.0 and 1.5 s) and intensity (means 8; 6; and 4 mA). The conditions were counterbalanced. Single-trial ERPs were extracted by wavelet-denoising. For each trial, the difference between the amplitudes of the N100 and P220 was measured. The N100-P220 of the first stimulus of a block was larger than those of stimuli 2 to 9, which did not differ and formed a plateau. The N100-P220 of the tenth stimulus was larger than that of the plateau, but smaller than that of the first stimulus. We propose that the response to the first stimulus reflects an orienting reaction, whereas the response to the last stimulus reflects an increase in the subjects' attention. An interaction between the VAS ratings and the N100-P220 differences was found: With stimulus repetition, the N100-P220 of the first stimulus and the plateau decreased. On the contrary, the VAS-ratings increased with stimulus repetition for the high and middle intensity conditions, whereas the VAS ratings remained constant for the low intensity conditions during the repetitive stimulation. We showed that it is indeed possible to track dynamic changes during stimulus repetition. However, the subjective intensities of the evoked sensations are not reflected in the N100-P220 component of the ERP. It remains to be analyzed whether other components of the ERP do correlate with the subjective experience.
doi:10.1016/j.ijpsycho.2008.05.459 Subjective mood estimation and cortical lateralization patterns J. Kaiser, M. Wyczesany Jagiellonian University, Institute of Psychology, Krakow, Poland Our study is concentrated on following questions:
• does particular valence of emotional stimuli influence consistently both changing of verbal mood estimation and patterns of cortical activity?
• is valence estimation of mood related to specific lateralization of cortical activity?
• does it refer to specific bands of EEG and region of the cortex? 56 subjects were divided into 3 groups. Each group received 8 min slide session consisting of 20 IAPS positive or negative or neutral pictures. Before and after the slide session an assessment of mood was done by two adjective checklists (UMACL and ADACL) followed immediately by a 1 min EEG recording. As an index of hemispheric imbalance the Lateralization Coefficient (LC) was chosen. In our analysis one set of variables are the checklists subjective scores and the second one are the LC magnitudes. Correlation methods were used to reveal possible co-variations of the data sets. The results indicate effectiveness of emotional stimuli in changing mood estimation as well as cortical activity. The direction of changes was related to emotional valence of slides. There is significant correlation between Hedonic scores and LC in beta3 and gamma bands — the more positive mood (Hedonic) the stronger left predomination was observed. Increase of negative mood (tension) was correlated significantly with right frontal theta1. Concluding: verbal estimation of affective qualities is related to specific patterns of cortical lateralization. These results support the assumption, that in some conditions people can describe their current internal state with reliability sufficient for scientific demand.
doi:10.1016/j.ijpsycho.2008.05.460 Neural correlates of body awareness and phantom sensation H. Flor Central Institute of Mental Health University of Heidelberg, Department of Cognitive and Clinical Neuroscience, Mannheim, Germany Recent neuroscientific evidence suggests that the brain processes not the physical but the perceived reality. We present data from phantom sensation
and illusory perception that show that primary somatosensory and motor cortex are active when movement of a limb is perceived in a mirror and that phantom pain is inversely correlated with this brain activation. Moreover, frontal and parietal regions are active when stimulation-induced referred sensations in the phantom are present and the activation of these regions is negatively correlated with the percept. We discuss how the brain processes illusionary phenomena and how this may be used in rehabilitation.
doi:10.1016/j.ijpsycho.2008.05.461 SYMPOSIUM 24: Oscillations, Anticipation and Memory Processes: Part II Symposium Chair: Nina N. Danilova (Russia); Co-Chair: Vilfredo de Pascalis (Italy) EEG determinants of the event-related potentials in an auditory Go/NoGo paradigm R.J. Barry University of Wollongong, Brain & Behaviour Research Institute and School of Psychology, Wollongong, Australia The recent literature, some from my laboratory, has emphasised the important role of phase-resetting of ongoing EEG activity in the generation of event-related potentials (ERPs). The present study examined two predictions of the phase-reset model of the ERP: that there is no post-stimulus change in the amplitudes of ongoing EEG activity, and that the ERP and ongoing EEG have the same sources. Although the first of these predictions may be weakened by the potential occurrence of stimulus-related EEG synchronization or desynchronization, the second remains robust. In this study, an auditory Go/NoGo task was used, in which stimuli of different frequencies were presented, with the frequency of the Go stimulus counterbalanced between subjects. Pre- and post-stimulus EEGs in traditional delta, theta, alpha and beta bands, and the averaged ERPs, were examined. EEG amplitudes were derived from each trial using FFTs on 0.5 s epochs pre- and poststimulus onset. These were averaged to obtain estimates of total activity before and after stimulus onset, each of which includes both ongoing activity unrelated to the stimulus, and stimulus-related activity. Averaged stimulusrelated EEG activity pre- and post-stimulus was similarly derived from the ERP. These data allow separate estimation of pre-stimulus ongoing activity independent of stimulus effects, and post-stimulus activity reflecting stimulus-related activity only, independent of ongoing activity. Topographic data from these were analysed to examine source stability. Topographies of the ERP peaks (N1, P2, N2, and P3) were also related to the topographies of the post-stimulus EEG data by step-wise multiple regression, seeking the EEG determinants of each ERP component. Results showed significant increases in delta and theta activity at stimulus onset, and differential changes in alpha and beta with Go vs. NoGo. There was also evidence of substantial changes in EEG source localization with these amplitude changes. These findings contradict both phase-resetting predictions, pointing to evoked activity contributing substantially to the different Go and NoGo ERP components. The close topographic associations between EEG band changes and ERP components, particularly the Go/NoGo differences, are discussed in relation to the genesis of the Go/NoGo ERPs.
doi:10.1016/j.ijpsycho.2008.05.462 Memory load effects and sources of variation in cognition-related brain oscillatory responses C.M. Krause Cognitive Science Unit, Department of Psychology, University of Helsinki, Helsinki, Finland The encoding of acoustic information typically elicits alpha frequency range EEG synchronization, the recognition or retrieval of the same material is accompanied by alpha frequency range EEG desynchronization. The alpha frequency synchronization during encoding is modulated by memory load (items to be stored) and the alpha desynchronization responses during recognition are modulated by probe stimulus properties (positive or negative probe). These phenomena in the EEG are robust and replicable on the group level, but recent observations indicate that both the inter- and intra-
Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205
EEGs (Cz) were measured while volunteers (n = 18) received electrical stimuli, duration 1 ms, on the phalange of the middle finger. Each volunteer received 9 conditions, each consisting of 3 blocks of 10 stimuli with a pause of 15 s between each block. The pain was rated on the VAS after each block. The conditions differed in interstimulus interval (0.5; 1.0 and 1.5 s) and intensity (means 8; 6; and 4 mA). The conditions were counterbalanced. Single-trial ERPs were extracted by wavelet-denoising. For each trial, the difference between the amplitudes of the N100 and P220 was measured. The N100-P220 of the first stimulus of a block was larger than those of stimuli 2 to 9, which did not differ and formed a plateau. The N100-P220 of the tenth stimulus was larger than that of the plateau, but smaller than that of the first stimulus. We propose that the response to the first stimulus reflects an orienting reaction, whereas the response to the last stimulus reflects an increase in the subjects' attention. An interaction between the VAS ratings and the N100-P220 differences was found: With stimulus repetition, the N100-P220 of the first stimulus and the plateau decreased. On the contrary, the VAS-ratings increased with stimulus repetition for the high and middle intensity conditions, whereas the VAS ratings remained constant for the low intensity conditions during the repetitive stimulation. We showed that it is indeed possible to track dynamic changes during stimulus repetition. However, the subjective intensities of the evoked sensations are not reflected in the N100-P220 component of the ERP. It remains to be analyzed whether other components of the ERP do correlate with the subjective experience.
doi:10.1016/j.ijpsycho.2008.05.459 Subjective mood estimation and cortical lateralization patterns J. Kaiser, M. Wyczesany Jagiellonian University, Institute of Psychology, Krakow, Poland Our study is concentrated on following questions:
• does particular valence of emotional stimuli influence consistently both changing of verbal mood estimation and patterns of cortical activity?
• is valence estimation of mood related to specific lateralization of cortical activity?
• does it refer to specific bands of EEG and region of the cortex? 56 subjects were divided into 3 groups. Each group received 8 min slide session consisting of 20 IAPS positive or negative or neutral pictures. Before and after the slide session an assessment of mood was done by two adjective checklists (UMACL and ADACL) followed immediately by a 1 min EEG recording. As an index of hemispheric imbalance the Lateralization Coefficient (LC) was chosen. In our analysis one set of variables are the checklists subjective scores and the second one are the LC magnitudes. Correlation methods were used to reveal possible co-variations of the data sets. The results indicate effectiveness of emotional stimuli in changing mood estimation as well as cortical activity. The direction of changes was related to emotional valence of slides. There is significant correlation between Hedonic scores and LC in beta3 and gamma bands — the more positive mood (Hedonic) the stronger left predomination was observed. Increase of negative mood (tension) was correlated significantly with right frontal theta1. Concluding: verbal estimation of affective qualities is related to specific patterns of cortical lateralization. These results support the assumption, that in some conditions people can describe their current internal state with reliability sufficient for scientific demand.
doi:10.1016/j.ijpsycho.2008.05.460 Neural correlates of body awareness and phantom sensation H. Flor Central Institute of Mental Health University of Heidelberg, Department of Cognitive and Clinical Neuroscience, Mannheim, Germany Recent neuroscientific evidence suggests that the brain processes not the physical but the perceived reality. We present data from phantom sensation
and illusory perception that show that primary somatosensory and motor cortex are active when movement of a limb is perceived in a mirror and that phantom pain is inversely correlated with this brain activation. Moreover, frontal and parietal regions are active when stimulation-induced referred sensations in the phantom are present and the activation of these regions is negatively correlated with the percept. We discuss how the brain processes illusionary phenomena and how this may be used in rehabilitation.
doi:10.1016/j.ijpsycho.2008.05.461 SYMPOSIUM 24: Oscillations, Anticipation and Memory Processes: Part II Symposium Chair: Nina N. Danilova (Russia); Co-Chair: Vilfredo de Pascalis (Italy) EEG determinants of the event-related potentials in an auditory Go/NoGo paradigm R.J. Barry University of Wollongong, Brain & Behaviour Research Institute and School of Psychology, Wollongong, Australia The recent literature, some from my laboratory, has emphasised the important role of phase-resetting of ongoing EEG activity in the generation of event-related potentials (ERPs). The present study examined two predictions of the phase-reset model of the ERP: that there is no post-stimulus change in the amplitudes of ongoing EEG activity, and that the ERP and ongoing EEG have the same sources. Although the first of these predictions may be weakened by the potential occurrence of stimulus-related EEG synchronization or desynchronization, the second remains robust. In this study, an auditory Go/NoGo task was used, in which stimuli of different frequencies were presented, with the frequency of the Go stimulus counterbalanced between subjects. Pre- and post-stimulus EEGs in traditional delta, theta, alpha and beta bands, and the averaged ERPs, were examined. EEG amplitudes were derived from each trial using FFTs on 0.5 s epochs pre- and poststimulus onset. These were averaged to obtain estimates of total activity before and after stimulus onset, each of which includes both ongoing activity unrelated to the stimulus, and stimulus-related activity. Averaged stimulusrelated EEG activity pre- and post-stimulus was similarly derived from the ERP. These data allow separate estimation of pre-stimulus ongoing activity independent of stimulus effects, and post-stimulus activity reflecting stimulus-related activity only, independent of ongoing activity. Topographic data from these were analysed to examine source stability. Topographies of the ERP peaks (N1, P2, N2, and P3) were also related to the topographies of the post-stimulus EEG data by step-wise multiple regression, seeking the EEG determinants of each ERP component. Results showed significant increases in delta and theta activity at stimulus onset, and differential changes in alpha and beta with Go vs. NoGo. There was also evidence of substantial changes in EEG source localization with these amplitude changes. These findings contradict both phase-resetting predictions, pointing to evoked activity contributing substantially to the different Go and NoGo ERP components. The close topographic associations between EEG band changes and ERP components, particularly the Go/NoGo differences, are discussed in relation to the genesis of the Go/NoGo ERPs.
doi:10.1016/j.ijpsycho.2008.05.462 Memory load effects and sources of variation in cognition-related brain oscillatory responses C.M. Krause Cognitive Science Unit, Department of Psychology, University of Helsinki, Helsinki, Finland The encoding of acoustic information typically elicits alpha frequency range EEG synchronization, the recognition or retrieval of the same material is accompanied by alpha frequency range EEG desynchronization. The alpha frequency synchronization during encoding is modulated by memory load (items to be stored) and the alpha desynchronization responses during recognition are modulated by probe stimulus properties (positive or negative probe). These phenomena in the EEG are robust and replicable on the group level, but recent observations indicate that both the inter- and intra-