Spatiotemporal remapping during saccades revealed by classification images analysis

Abstract

It is well known that saccades cause profound transient effects to the receptive fields of parietal cortical cells and also to human perception. Using the “agnostic” psychophysical tool of Classification Image Analysis, we measured the dynamic changes of the spatio-temporal impulse response function of perceptual mechanisms at the time of saccades. Three subjects detected (in 2AFC) the presence of a near-threshold white bar briefly flashed (21 ms) on a 24° × 1.5° strip of dynamic white noise at different times from the onset of a 18° voluntary saccade. We computed the mean kernel of activation of the perceptive field for bars presented at different times before of after saccadic onset. Well before or well after the saccade, we reproduce the well known spatio-temporally separable perceptive field that extended over about 6° and 60 ms. Just before saccades, the spatial-temporal spread of the perceptive field increased to 12° by 120 ms; and more importantly, the function became oriented in space-time. At saccadic onset, the kernel presented two distinct foci, one at −45 ms the other at 50 ms after saccadic onset. These two foci correlate well with the temporal distortions known to occur around the time of saccades (Binda et al, J. Neurosc., 2009). The interval between the two foci shows a strong suppression of the signal, with a time course similar to the known dynamics of saccadic suppression. These data provide direct support for the existence in the human brain of remapping of neuronal receptive fields at the time of saccades. They further support the suggestion that receptive fields become transiently oriented in space-time around the time of saccades allowing trans-saccadic integration of pre- and post-saccadic visual signals.

This study has been funded by the EC project STANIB (FP7-ERC).