Attentional Modulation of Chromatic and Achromatic Visual Evoked Potentials by Task Relevant Stimuli in Separate Hemi-fields

摘要

Prior research has shown that the chromatic pattern-onset VEP recorded along centerline (OZ) is robust to attentional manipulations when test and distractor stimuli are either superimposed or spatially separated. These results suggest that the chromatic VEP response is occurring early (V1) and may not be sensitive to feedback from attentional mechanisms. We report here studies of chromatic and achromatic VEP responses recorded over V1 on the centerline (Oz) and lateralized over each hemisphere (O1 and O2).in the presence of distractor and test stimuli located in disparate hemifields. VEP were recorded to both distractor and test simultaneously using a frequency-tagged averaging technique. Results indicated that for stimuli that are equated in psychophysical magnitude and using a distractor similar to the test, small but significant attentional modulations of the chromatic waveform amplitudes are revealed. In addition, we explore effects of attentional modulation across both the chromatic (L a?? M) and (S a?? (L + M)) and the achromatic visual pathways. The results suggest that the Chromatic Onset VEP is robust to attentional effects unless the distractor is similar to the test and the task is difficult. Under such conditions small but significant attentional affects can be revealed.