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Jennifer Highsmith, Chad Duncan, Sean O'Neil, Eric Roth, Michael Crognale; Effects of selective attention on the chromatic VEP: Task-relevant stimuli. Journal of Vision 2008;8(6):989. doi: 10.1167/8.6.989.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: When viewing spatially separated visual stimuli, performance is often compromised for unattended stimuli. This has been reported for both behavioral and electrophysiological measurements. Performance is further compromised when the unattended stimulus is similar to the attended stimulus (task-relevant). In electrophysiological studies attentional effects are not typically seen in early responses, and are particularly absent in the pattern-onset VEP. However studies have reported larger attentional effects under conditions of selective attention when the attended and unattended stimuli are similar. The present study used chromatic pattern on-set VEP stimuli to measure attentional modulations at early visual stages with similar attended and unattended stimuli. Methods: 8 subjects fixated on a central location with chromatic pattern on-set stimuli presented to either visual field. Target and non-target stimuli were chromatic 1cycle/degree horizontal sine wave gratings presented in an on/off manner. In one condition subjects directed attention to the left visual field where various chromatic stimuli were displayed (100ms on/400ms off) and VEPs recorded while a temporally unsynchronized pattern was displayed (100ms on/ 500ms off) in the right visual field. In another condition the stimulus presentation remained the same, however subjects directed attention to the right visual field. Attention was monitored by having subjects press a button whenever a predetermined chromatic stimulus appeared. Results: No significant change in waveform amplitude or latency was found between conditions. Waveform characteristics of chromatic pattern on-set VEP do not appear to be effected by attentional shifts even when using task-relevant distracter stimuli. These data are consistent with our previous data employing other attentional shift paradigms. Conclusion: Combined with our previous results, the data suggest that monitoring attentional state is not necessary when recording chromatic onset VEPs as the waveforms will be unaffected by attentional shifts as long as gaze is directed toward the stimulus.
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