Low-Level Visual Information is Maintained Across Saccades by a 'Soft Hand-Off' between Visual Processing Areas

Abstract

Subjective visual experience of a rich, detailed visual scene seems continuous despite us making several saccadic eye movements every second which radically change retinal input. Here, we investigated the time course of low-level visual information processing in the brain by decoding spatial frequency of an attended, stationary stimulus that changed from one visual hemifield to another due to a horizontal saccadic eye movement. Magneto-encephalography (MEG) was recorded while human participants made a large horizontal saccade and monitored the orientation of a grating stimulus, making spatial frequency task-irrelevant. Separate trials, in which participants maintained fixation, were used to train a classifier that was tested during saccade trials. Decoding performance showed that information about spatial frequency was present in the original retinotopic areas before, during and up to around 200 ms after the saccade. Post-saccadic information rapidly ramped up within a few tens of milliseconds, allowing for rapid decoding from the new retinotopic areas. There was an overlap of over 100 ms during which decoding was significant from both pre- and post-saccadic processing areas. These results suggest that the apparent richness of perception across saccades may be supported by the continuous availability of the low-level spatial frequency information that supports gist, object and ensemble perception, with a “soft hand-off” of this information during the initial visual processing sweep of the new fixation. Such a mechanism does not require remapping of low-level visual information before the saccade.