July 29 –
Aug. 3, 2002
Scott Makeig, Institute for Neural Computation,
Universityof California , San Diego La Jolla CA
Symposium on EEG Coherence
Brainstorms: Independent EEG processes transiently synchronize in response to cognitive challenges
Noninvasively recorded high-density EEG signals contain a wealth of information about cortical synchronization in multiple frequency bands and cortical domains. However, the goal of event-related coherence methods for modeling functional macroscopic brain dynamics is compromised by the use of scalp EEG signals that each sum activities occurring in multiple EEG domains. The approach I present here uses independent component analysis to separate the activity of different domains of cortical synchrony and to remove non-neural artifacts, followed by wavelet-based time/frequency analysis and single-trial based visualization methods to detect brain dynamic events occurring in response to cognitive challenges. An important class of such events are coherent theta band phenomena that briefly organize synchronous brain activity within otherwise-independent cortical domains in response to cognitive challenges. I give examples from EEG responses to task-relevant stimuli in stimulus detection, memory encoding and Erickson flanker tasks. I show, in particular, that theta dynamic events underlie the error-related negativity (ERN) following errors committed in forced choice responses under time pressure. Source location estimates of the EEG domains linked by these dynamic events suggest they form transient fronto-parietal networks that may serve to regulate top-down attentional re-tuning of motor and perceptual brain areas in light of the perceived consequences of previous attentional orientation.