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Abstract:
The latencies of visually guided saccadic eye movements can form bimodal distributions. The 'express saccades' associated with the first mode of the
distribution are thought to be generated via an anatomical pathway different from that for the second mode, which comprises regular saccades. The following
previously published observations are the basis for a new alternative model of these effects: (i) visual stimuli can cause oscillations to appear in the
electroencephalogram; (ii) visual stimuli can cause a negative shift in the electroencephalogram that lasts for several hundreds of milliseconds; and (iii) negativity in
the electroencephalogram can be associated with reduced thresholds of cortical neurons to stimuli. In the new model both express and regular saccades are
generated by the same anatomical structures. The differences in saccadic latency are produced by an oscillatory reduction of a threshold in the saccade-generating
pathway that is transiently produced under certain stimulus paradigms. The model has implications regarding the functional significance of spontaneous and
stimulus-induced oscillations in the central nervous system.
