Poster A5, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Neural generators and fast dynamics of the task-relevant P3a ERP
Lizzy Blundon1, Lawrence Ward1; 1University of British Columbia
The P300, an ERP response associated with context updating and attentional resource allocation to oddball stimuli, contains at least two subcomponents, the P3a and the P3b. The P3a is observed in response to rare, salient, task-irrelevant oddballs, and may indicate exogenous attention orienting toward novel stimuli. The P3b is associated with target identification, and may reflect stimulus encoding mechanisms associated with context updating. It is believed that every P300 contains a mix of both P3a and P3b subcomponents; the relative contribution of each depends on the stimulus context in which the P300 is observed. We recorded EEG during an oddball task that featured sequences of identical tone patterns that differed only by a single feature. The P300 response to rare, salient, oddball targets contained strong contributions from both P3a and P3b subcomponents, providing evidence for a task-relevant P3a. Using independent component analysis and single dipole fitting, we inferred the neural generators for each subcomponent from the scalp EEG. Among the primary neural generators of the P3a is the anterior cingulate cortex and, possibly, posterior parietal cortex, whereas the P3b is associated most with activity in posterior cingulate cortex and superior parietal lobules. Phase locking value and narrow band transfer entropy were used to characterize the timing of the functional and effective connectivity, respectively, within these networks with respect to timing of the P300. The connectivity dynamics were found to mirror the timing of each subcomponent, with connectivity in the P3a network occurring earlier than that in the P3b network.
Topic Area: ATTENTION: Auditory