Contrast dependence of lambda response

Lambda response is obtained by averaging EEGs time-locked to the offset of saccadic eye movements (saccades) with a peak latency of about 100 ms from the offset of saccades. Lambda response is thought to be evoked by the inflow of visual information after the termination of the saccade. The purpose of the present study is to evaluate the effect of stimulus contrast on lambda response. Eighteen normal adults participated in the experiment. The stimuli were vertical black-and-white sinusoidal gratings of three spatial frequencies (0.5, 1 and 3 cycles/degree, cpd). Stimulus contrast ranged from 0% to 96%. The subject made horizontal saccades between two fixation points at a constant pace. At spatial frequencies of 0.5 and 1 cpd, the peak latency of lambda response decreased as the stimulus contrast increased. At spatial frequency of 3 cpd, the peak latency did not vary with the stimulus contrast. The peak amplitude of lambda response did not vary with the stimulus contrast at spatial frequencies of 0.5 and 1 cpd, but it did at spatial frequency of 3 cpd. These results indicate that the effect of stimulus contrast on lambda response changes according to the stimulus spatial frequency. They also suggest that lambda response may be a useful index of visual information processing with eye movements.