Abstract
Introduction: Attention has been shown to modulate visual tasks. For example, divided attention causes decrements in performance on psychophysical tasks. Electrophysiological measures (i.e. steady-state and multi-focal VEPs) show a decrease in waveform amplitude and an increase in latency with divided attention. In many of these studies VEP stimuli and distracter stimuli are presented to separate eyes with binocular rivalry as a possible consequence. It has been shown that electrophysiological responses for the non-dominant (unattended) stimulus are compromised during binocular rivalry.
This study was done to determine if decrements in responses to chromatic stimuli could be found when conditions leading to binocular rivalry are eliminated. Chromatic pattern on-set VEPs were recorded under conditions of divided attention with stimuli presented to both eyes simultaneously.
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. Attention was assessed by task accuracy.
Results: Subjects' responses for the baseline, attended, and unattended conditions showed no significant differences in amplitude and latency for the large negative component of the chromatic onset waveform.
Conclusions: Under conditions that preclude binocular rivalry, the chromatic pattern on-set VEP does not change with attentional modulation.