The impact of microsaccades on vision: towards a unified theory of saccadic function

Martínez-Conde, Susana; Otero‐Millan, Jorge; Macknik, Stephen L.

doi:10.1038/nrn3405

Cited by 424 publications

(410 citation statements)

References 130 publications

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“…Saccadic eye movements are known to play multiple roles in vision-that is, they foveate high-interest targets, correct gaze errors, and search and integrate general information about the environment to stitch together the perception of a scene (7,35). Likewise, many microsaccade functions have been proposed (31), including the prevention of visual fading and the restoration of faded visual targets (36)(37)(38), the control of fixation position (3,39), and improved visual performance in high-acuity tasks (24,40). Our results point to a similarity in function for microsaccades and saccades, and suggest that all of the saccadic roles may be common to microsaccades, including the scanning and exploration of visual objects and scenes traditionally ascribed to (large) saccades.…”

Section: Discussionmentioning

confidence: 99%

“…Van Gisbergen and coworkers showed that the activity of excitatory burst neurons in the pontine reticular formation encodes microsaccades and saccades (30). No studies to date have conducted recordings from inhibitory burst neurons in connection with microsaccades, however (31). Omnipause neurons in the raphe stop firing during both saccades and microsaccades (32,33), and population activity in the superior colliculus map generates microsaccades and saccades in equivalent fashion (9,34).…”

Section: Discussionmentioning

confidence: 99%

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An oculomotor continuum from exploration to fixation

Otero‐Millan

Macknik

Langston

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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110

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During visual exploration, saccadic eye movements scan the scene for objects of interest. During attempted fixation, the eyes are relatively still but often produce microsaccades. Saccadic rates during exploration are higher than those of microsaccades during fixation, reinforcing the classic view that exploration and fixation are two distinct oculomotor behaviors. An alternative model is that fixation and exploration are not dichotomous, but are instead two extremes of a functional continuum. Here, we measured the eye movements of human observers as they either fixed their gaze on a small spot or scanned natural scenes of varying sizes. As scene size diminished, so did saccade rates, until they were continuous with microsaccadic rates during fixation. Other saccadic properties varied as function of image size as well, forming a continuum with microsaccadic parameters during fixation. This saccadic continuum extended to nonrestrictive, ecological viewing conditions that allowed all types of saccades and fixation positions. Eye movement simulations moreover showed that a single model of oculomotor behavior can explain the saccadic continuum from exploration to fixation, for images of all sizes. These findings challenge the view that exploration and fixation are dichotomous, suggesting instead that visual fixation is functionally equivalent to visual exploration on a spatially focused scale.free-viewing | fixational eye movements | miniature eye movements | fixational saccades | natural images C lassic and current vision studies distinguish between visual exploration, characterized by the alternation of saccades and brief fixation periods, and attempted visual fixation, where subjects maintain relative gaze stability despite continuous but minute fixational eye movements (i.e., microsaccades, slow drift, and oculomotor tremor) (1-7). The theoretical separation between exploratory gaze shifts and attempted fixation dates back to the discovery of fixational eye movements in the early 1900s (2-4), and remains central to contemporary discourse in visual, cognitive, and oculomotor research (8). However, mounting evidence in support of a common generator for both exploratory saccades and fixational microsaccades (refs. 9-12 but see ref. 13) brings into question whether such a dichotomy is justified. Instead, it may be that saccades and microsaccades form an oculomotor continuum along the entire spectrum of exploratory scales, with classical exploratory saccades at one end and classical fixational microsaccades at the other end. In that case, it might be baseless to distinguish between fixational and exploratory behaviors. Recent studies have identified abnormal dynamics of saccades and microsaccades as potential diagnostic markers of neurological disease (14-16); thus, the frame of reference proposed here may have important clinical implications concerning the role of the affected brain centers in the patients' oculomotor behavior.To establish such a framework, one must first reconcile any known discrepancy between the ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

An oculomotor continuum from exploration to fixation

Otero‐Millan

Macknik

Langston

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

110

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“…Microsaccades were distinguished from macrosaccades using an amplitude threshold of 1° (Martinez-Conde et al, 2013) and the median microsaccade amplitude was 0.65°(M1: 0.71°, M2: 0.65°, M3: 0.62°). This is larger than in most studies, although there is also considerable variability between the average microsaccade amplitudes described in past reports, which include 0.8° (Bair and O'Keefe, 1998) (Ko et al, 2010;Poletti and Rucci, 2010), and 0.23° ( Hafed et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Microsaccade Control Signals in the Cerebellum

et al. 2015

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Microsaccades, the small saccades made when we try to keep the eyes still, were once believed to be inconsequential for vision, but recent studies suggest that they can precisely relocate gaze to tiny visual targets. Because the cerebellum is necessary for motor precision, we investigated whether microsaccades may exploit this neural machinery in monkeys. Almost all vermal Purkinje cells, which provide the eye-related output of the cerebellar cortex, were found to increase or decrease their simple spike firing rate during microsaccades. At both the single-cell and population level, microsaccade-related activity was highly similar to macrosaccade-related activity and we observed a continuous representation of saccade amplitude that spanned both the macrosaccade and microsaccade domains. Our results suggest that the cerebellum's role in fine-tuning eye movements extends even to the oculomotor system's smallest saccades and add to a growing list of observations that call into question the classical categorical distinction between microsaccades and macrosaccades.

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“…Selection does not only control the access of task-relevant objects to working memory, but also provides spatial coordinates for upcoming eye movements. Research on saccades and microsaccades [65][66][67] has provided important insights into the control of selective attention during search in real-world visual scenes. For example, semantic and spatial expectations linked to particular scene contexts strongly constrain which parts of a scene will be visually examined [65,68], which demonstrates that high-level world knowledge plays an important role for attentional guidance and selection.…”

Section: Concluding Commentsmentioning

confidence: 99%

The neural basis of attentional control in visual search

Eimer

2014

Trends in Cognitive Sciences

252

205

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How do we localize and identify target objects among distractors in visual scenes? The role of selective attention in visual search has been studied for decades, and the outlines of a general processing model are now beginning to emerge. Attentional processes unfold in real time, and this review describes four temporally and functionally dissociable stages of attention in visual search (preparation, guidance, selection, and identification). Insights from neuroscientific studies of visual attention suggest that our ability to find target objects in visual search is based on processes that operate at each of these four stages in close association with working memory and recurrent feedback mechanisms.

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The impact of microsaccades on vision: towards a unified theory of saccadic function

Cited by 424 publications

References 130 publications

An oculomotor continuum from exploration to fixation

An oculomotor continuum from exploration to fixation

Microsaccade Control Signals in the Cerebellum

The neural basis of attentional control in visual search

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