Visual perception and the retinal mosaic. II. The influence of eye-movements on the displacement threshold.

Poletti

2015

Annu. Rev. Vis. Sci.

176

151

Humans and other species explore a visual scene by rapidly shifting their gaze 2-3 times every second. Although the eyes may appear immobile in the brief intervals in between saccades, microscopic (fixational) eye movements are always present, even when attending to a single point. These movements occur during the very periods in which visual information is acquired and processed and their functions have long been debated. Recent technical advances in controlling retinal stimulation during normal oculomotor activity have shed new light on the visual contributions of fixational eye movements and their degree of control. The emerging body of evidence, reviewed in this article, indicates that fixational eye movements are important components of the strategy by which the visual system processes fine spatial details, enabling both precise positioning of the stimulus on the retina and encoding of spatial information into the joint space-time domain.

Section: Visual Functions Of Inter-saccadic Fixational Movementsmentioning

confidence: 92%

Control and Functions of Fixational Eye Movements

Poletti

2015

Annu. Rev. Vis. Sci.

176

151

“…However, it has long been questioned whether fixational jitter might play a much more fundamental role than preventing neural adaptation. Several theories have argued for a contribution of this motion to the processing of fine spatial detail (Averill and Weymouth, 1925;Marshall and Talbot, 1942;Arend, 1973;Arieli, 2001, 2012;. These theories differ in their specifics, but share the common hypothesis that the fixational motion of the retinal image is necessary for encoding spatial information in the temporal domain (i.e., for structuring, rather than just refreshing, neural activity).…”

Section: Discussionmentioning

confidence: 99%

The Visual Input to the Retina during Natural Head-Free Fixation

Aytekin¹,

Victor

Journal of Neuroscience

2014

Head and eye movements incessantly modulate the luminance signals impinging onto the retina during natural intersaccadic fixation. Yet, little is known about how these fixational movements influence the statistics of retinal stimulation. Here, we provide the first detailed characterization of the visual input to the human retina during normal head-free fixation. We used high-resolution recordings of head and eye movements in a natural viewing task to examine how they jointly transform spatial information into temporal modulations. In agreement with previous studies, we report that both the head and the eyes move considerably during fixation. However, we show that fixational head and eye movements mostly compensate for each other, yielding a spatiotemporal redistribution of the input power to the retina similar to that previously observed under head immobilization. The resulting retinal image motion counterbalances the spectral distribution of natural scenes, giving temporal modulations that are equalized in power over a broad range of spatial frequencies. These findings support the proposal that "ocular drift," the smooth fixational motion of the eye, is under motor control, and indicate that the spatiotemporal reformatting caused by fixational behavior is an important computational element in the encoding of visual information.

“…Since the luminance modulations resulting from fixational eye movements contain spatial information at individual retinal locations, it has long been postulated that fixational eye movements may be a critical component of a dynamic strategy for encoding space, an approach that converts spatial information into temporal structure [11, 12, 13, 14, 15, 16, 17, 18]. While these theories differ in the specific mechanisms they propose, they share the common hypothesis that fixational instability plays a central role in structuring —rather than the just refreshing —neural activity for establishing spatial representations.…”

Section: The Unsteady Eyementioning

confidence: 99%

The unsteady eye: an information-processing stage, not a bug

Trends in Neurosciences

Victor

2015

176

178

How is space represented in the visual system? At first glance, the answer to this fundamental question appears straightforward: spatial information is directly encoded in the locations of neurons within maps. This concept has long dominated visual neuroscience, leading to mainstream theories of how neurons encode information. However, an accumulation of evidence indicates that this purely spatial view is incomplete, and that even for static images, the representation is fundamentally spatiotemporal. The evidence for this new understanding centers on recent experimental findings concerning the functional role of fixational eye movements, the tiny movements humans and other species continually perform, even when attending to a single point. Here, we review some of these findings and discuss their functional implications.