Linking pre-saccadic to post-saccadic stimuli in the visual field
Saccadic eye motion evolved in early vertebrates as an adaptive mechanism to view more areas of a visual scene with the central fovea, and therefore increase overall resolution. Theoretically, it should come at the cost of making it more difficult to link a sequence of objects together, since these saccades would confuse you as to what exactly you are currently looking. However, our visual system compensates for upcoming saccades, resulting in three odd results:
1) Visual fields change their position in shape in real time in order to adjust to the saccade target. For example, in V4, receptive fields generally shift towards the upcoming saccade and modulate their size.
2) Very near to the time that the saccade moves (it’s onset), our perception is that briefly flashed stimuli are closer to the saccade target than they actually are. This is known as peri-saccadic compression, and there ought to be a wikipedia page for it.
3) In experiments that require subjects to both execute a target-directed saccade and discriminate an object (choose it from among a set, I presume), visual discrimation is naturally strongest when the stimuli is located near the target of the saccade.
Their model attempts to explain these distinct phenomena through oculomotor feedback, and show how the brain links the pre-saccadic visual field to the post-saccadic one. Mathematically their model is complex, and they do so not to yield an arbitrarily higher fit, but in order to make it more consistent with the anotomical constraints of visual receptors. Indeed, some of their parameters were so complex that they were forced to estimate their values because of a lack of independently found data to build upon. Nevertheless, their model is fascinating and their predictions robust. Check it out, it’s ungated.
Reference
Hamker FH, Zirnsak M, Calow D, Lappe M 2008 The Peri-Saccadic Perception of Objects and Space. PLoS Computational Biology 4(2): e31 doi:10.1371/journal.pcbi.0040031