Saccades and shifting receptive fields: anticipating consequences or selecting targets?

Abstract

Saccadic eye movements cause frequent and substantial displacements of the retinal image, but those displacements go unnoticed. It has been widely assumed that this perceived stability emerges from the shifting of visual receptive fields from their current, presaccadic locations to their future, postsaccadic locations in anticipation of the retinal consequences of saccades. Although evidence consistent with this anticipatory remapping has accumulated over the years, more recent work suggests an alternative view. In this opinion article, we examine the evidence of presaccadic receptive field shifts and their relationship to the perceptual changes that accompany saccades. We argue that both reflect the selection of targets for saccades rather than the anticipation of a displaced retinal image.

Neuronal Response Gain Enhancement prior to Microsaccades

“…Indeed, microsaccades cause perceptual mislocalizations that are believed to be a hallmark of perceptual stability mechanisms [24]. Therefore, attention may be a general component of peri-saccadic perceptual stability [27].…”

“…Grating contrast (Lmax À Lmin / Lmax + Lmin) was 5%, 10%, 20%, 40%, or 80%, and phase was randomized. Grating size (filling the RF) was large enough to avoid a potential ''micro'' form of changing/shifting RF's around saccades [27,28]. If such changes occur around microsaccades, they would be small and canceled with large stimuli.…”

“…It might also be the case that these changes share characteristics with changes observed when attentional allocation is instructed. For example, if microsaccade-related preparatory activity in the superior colliculus (SC) [21] were to provide a ''gain'' modulation signal for visually evoked neuronal activity [24], similar to how it might do with large saccades [25][26][27][28][29][30], then response enhancement could potentially be observed for stimuli appearing before microsaccades, independent of whether a task involved attention. Thus, response enhancement, an attentional signature, can also occur in tight synchrony with individual microsaccades.…”

Dissociation of forward and convergent remapping in primate visual cortex

“…Until about 25 years ago, visual receptive fi elds were thought to be determined entirely by the pattern of retinal inputs, so it was quite surprising to fi nd neurons in primate cortex with receptive fi elds that changed position every time a saccade was executed [1]. Although this discovery has fi gured prominently into theories of visual perception, there is still much debate about the nature of the phenomenon: Some studies report forward remapping Correspondence [1][2][3], in which receptive fi elds shift to their postsaccadic locations, and others report convergent remapping, in which receptive fi elds shift toward the saccade target [4]. These two possibilities can be diffi cult to distinguish, particularly when the two types of remapping lead to receptive fi eld shifts in similar directions [5], as was the case in virtually all previous experiments.…”

“…An emerging pattern of results shows that the perisaccadic responses of V4 neurons recall the locations of past stimuli [3] and anticipate potential future stimuli [6,10], in addition to their well-known roles in shape recognition and attention. The fact that these different responses are present in the same area, and often in the same neurons, has profound implications for theories of spatial representations in the primate brain [2,4].…”