Abstract
Introduction: Attention plays a role in visual tasks. Decrements in performance are reported when attention is divided between separate tasks. Psychophysical indices (reaction time and percent correct) are often employed to measure attentional effects. Electrophysiological measures using steady state and multi-focal VEPs show decrements in waveform amplitude with divided attention. These studies were done with VEP stimuli and distracter stimuli presented to separate eyes, invoking mechanisms of both attention and interocular rivalry. This study used a chromatic pattern on-set VEP under conditions of divided attention with stimuli presented to both eyes simultaneously to determine if decrements in waveforms could be found when conditions possibly leading to binocular rivalry are eliminated.
Methods: VEP Stimuli were l cycle/degree horizontal sine wave patterns (on-set mode 100ms on/400ms off). Distracter stimuli were letters superimposed over the VEP stimuli. Subjects attended to either the letters or the gratings and pressed a button when a predetermined stimulus appeared.
Results: Most subjects showed no change in the large negative component of the chromatic onset response.
Conclusions: The chromatic pattern on-set VEP does not appear to be affected by conditions of divided attention when target and distracter stimuli are presented to both eyes simultaneously.