Poster Session II: Attentional modulation of the achromatic and chromatic reversal VEP.

Previous literature has consistently revealed attentional modulation of the Visual Evoked Potential (VEP) response to achromatic pattern reversal stimuli but little to no attentional modulation of the VEP response to chromatic pattern onsets. Magnetic Resonance Imaging (MRI) research, however, has reported modulation of the responses to both achromatic and chromatic pattern reversal stimuli. Numerous methodological differences including mode of presentation, stimulus contrast, and attentional demand, make comparison of these results difficult. In this study, we report the results of experiments using comparable perceptual contrasts, pattern reversals, and a coextensive and highly-demanding, multiple object tracking (MOT) task. Our findings support prior VEP results indicating that although achromatic VEPs are modulated by attention, chromatic VEPs are more robust to attentional modulation, even for highly demanding distractor tasks. We also found that when compared to a non-attentional condition, the attenuation of the VEP when attending to the MOT task was greater in magnitude than the enhancement of the VEP when attending to the VEP stimulus. This supports prior conclusions, that while avoiding active distraction is likely important, insuring an "attentive state" is not always necessary when recording VEPs. Further experiments are underway to investigate why attentional modulation of chromatic signals in early visual cortex are observed in MRI but not VEP recordings.