EEG/ERP Control Process Separation

Transcription

1 EEG/ERP Control Process Separation Gwen A. Frishkoff & Don M. Tucker It may be possible to develop monitoring devices to provide realtime readout of activity within and between subsystems of the control network. Electrical Geodesics, Inc. ACC 0.6 % BOLD -0.2 PC 1.2 % BOLD -0.2 DLPFC 0.8 % BOLD -0.2 Frishkoff, Schneider & Tucker 2 12 ONR Grantee Meeting

2 Goal: Tracking Network Interactions with High-Density EEG Goal Processor Activity Monitor Attention Controller PPC ACC DLPFC THAL MTL Relay Episodic Store Schneider & Chein, 2003 Frishkoff, Schneider & Tucker ONR Grantee Meeting

3 Geodesic Sensor Net (Electrical Geodesics, Inc.) 128-channel 256-channel Frishkoff, Schneider & Tucker ONR Grantee Meeting

4 ERP Study Gwen Frishkoff, Ph.D. & Oregon Collaborators NeuroInformatics Center, University of Oregon Electrical Geodesics, Inc. (Eugene, Oregon) Pilot work with 13 subjects 2 hours of data on the CPS line task ERP/EEG Analyses Conventional ERPs (complete) 2-second, stimulus-locked averages Topographic mapping with dense array Advanced EEG & ERP analyses (ongoing) Mapping slow activity (15-second ERPs) Joint Time Frequency (wavelet) analyses Spatiotemporal source localization Integration with fmri results for individual subjects Frishkoff, Schneider & Tucker ONR Grantee Meeting

5 CPS Line Search: 3 Factors Attentional Search + Single location Multiple locations + Easy discrimination Hard discrimination Attentional comparison Target Distractors Target Distractors Early vs. Late comparison Switch period (first 15 sec) vs. Probe period (last 15 sec) Frishkoff, Schneider & Tucker ONR Grantee Meeting

6 Experiment Tasks Fixation Blink Control Easy Search Easy Compare Easy Search Hard Compare Hard Search Easy Compare Hard Search Hard Compare Frishkoff, Schneider & Tucker ONR Grantee Meeting

7 Frishkoff, Schneider & Tucker ONR Grantee Meeting

8 Major effects for Conventional ERP ERP analyses of line search show strong ERP activation with differential spatial and temporal patterns that are analogous to the FMRI results. Basic phenomena Effect of search difficulty has a parietal distribution Effect of comparison has a frontal distribution Task switching shows frontal midline distribution Time course effects over extended processing Drop out of frontal areas as processing continues Maintenance in the search condition of parietal activation Frishkoff, Schneider & Tucker ONR Grantee Meeting

9 Search difficulty effect + Switch Period: Strong engagement of frontal and posterior parietal areas (~ ms) Probe Period: Frontal activity drops out. Enchanced midline activation (~ ms) Frishkoff, Schneider & Tucker ONR Grantee Meeting

10 Comparison difficulty effect Medial Frontal Effect: Hard less negative (~ ms) Right Parietal Effect: Hard more negative Comparison Effects over medial frontal (ACC) and right parietal areas drop out in second half. Frishkoff, Schneider & Tucker ONR Grantee Meeting

11 Dynamics in ERP Early versus late we see substantial changes in CP network over time paralleling the fmri results These results point to dynamic interactions between within the CP subareas and between the CP network and sensorimotor regions Individual differences in ERP dynamics are impressive, with some participants showing strong stimulus-evoked activity over all regions, and others showing oscillations that are confined to orbitofrontal regions These dynamics may be related to differences in expertise (CP on the line task). Further studies are planned to examine this hypothesis. Frishkoff, Schneider & Tucker ONR Grantee Meeting

12 Work in Progress 1 Mapping sustained (blocked) versus phasic (stimuluslocked) activity Advanced signal analysis for artifact removal using APECS (Automated Protocol for Electromagnetic Component Separation) ICA, PCA, SOBI, Wavelets NeuroInformatics Center, University of Oregon Addressing the problem of superposition Techniques for ERP temporal and spatial component separation (PCA, ICA) Integration of ERP and fmri data Spatiotemporal Source Analysis, seeding dipoles from centroids of activation in fmri data (BESA & Brain Voyager) Frishkoff, Schneider & Tucker ONR Grantee Meeting

13 Work in Progress 2 Joint Time-Frequency (wavelet) analyses allow us to track synronization of activity within particular frequency bands (alpha, gamma, etc.) may point to dynamic interactions (i.e., coherence) between CP regions Don Tucker, Electric Geodesics, Inc. Bob Frank, NeuroInformatics Center Vince Samar, University of Rochester Frishkoff, Schneider & Tucker ONR Grantee Meeting

14 Future Prospects New studies to refine and elaborate ERP characterization of CP network activity Tracking degree of automaticity Training on CP strategies to track & enhance performance Frishkoff, Schneider & Tucker ONR Grantee Meeting