Coding of Microsaccades in Three-Dimensional Space by Premotor Saccadic Neurons

Horn, Marion R. Van; Cullen, Kathleen E.

doi:10.1523/jneurosci.5054-11.2012

Cited by 38 publications

(29 citation statements)

References 41 publications

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“…The reciprocally innervating circuit of OPNs and LLBNs transforms tectal activity into saccadic burst (Hafed et al 2009;Otero-Millan et al 2011;Rolfs et al 2008). Thus, microsaccades and saccades share many physiological principles and neural substrates (Girard and Berthoz 2005;Hafed et al 2009;Rolfs et al 2008;Van Horn and Cullen 2012). Our experiments tested whether perturbations that are known to alter the properties of visually guided saccades also affect microsaccade.…”

Section: Discussionmentioning

confidence: 99%

“…Fixational eye movements such as drifts and microsaccades collectively change the foveal position of the image and prevent neural adaptation and visual fading (Simon et al 1984;Troncoso et al 2008;Van Horn and Cullen 2012). Microsaccades also direct the gaze back to the target after inherent drifts in the eye position (Martinez-Conde 2006; Ratliff and Riggs 1950;Young and Sheena 1975).…”

Section: Introductionmentioning

confidence: 99%

“…Both classes of eye movements follow stereotypical amplitude-velocity relationship (Girard and Berthoz 2005;Otero-Millan et al 2008;Zuber et al 1965). Generation of saccades and microsaccades utilizes the same neural substrate (Girard and Berthoz 2005;Hafed et al 2009;Rolfs et al 2008;Van Horn and Cullen 2012).…”

Section: Introductionmentioning

confidence: 99%

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Experimental tests of hypotheses for microsaccade generation

Ghasia

Shaikh

2015

Exp Brain Res

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Fixational eye movements such as microsaccades are important to prevent fading. These miniature eye movements are also necessary to redirect gaze to the target after a drift. Generation of saccades and microsaccades utilizes common neural substrates. We, therefore, hypothesized that physiological modulators of saccades should also affect microsaccades. Test of this hypothesis will also provide support for the models of a microsaccade generation. We performed two experiments. In the first experiment, complete darkness led to a decrease in the frequency and velocity, but increased the amplitude of microsaccades. In the second experiment, active eyelid closure further reduced the velocity and frequency of microsaccades, but increased their amplitude. Darkness reduces the superior colliculus activity leading to a reduction in the velocity and frequency of microsaccades. Eye closure might cause sustained inhibition of the omnipause neurons. Subsequent disinhibition of the burst neurons might cause a reduction in the post-inhibitory rebound firing resulting in a decreased velocity of microsaccades. Sustained inhibition of the omnipause neurons could also reduce the inhibitory drive that would otherwise abort microsaccades. Hence, by inhibiting the activity of omnipause neurons, the eye closure could increase the amplitude of microsaccades.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental tests of hypotheses for microsaccade generation

Ghasia

Shaikh

2015

Exp Brain Res

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“…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). The hypothesis of a fixation-exploration continuum reconciles the dynamics of oculomotor behavior with the proposal of a common microsaccade-saccade generator (9-11), and it moreover elucidates previously unexplained results concerning the precise relationship between saccades and microsaccades, such as the finding that subjects can make voluntary saccades that are as small as fixational microsaccades (12).…”

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.

106

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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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“…This results in a double advantage: First, the method works well even if only monocular data are available (Figure 7). Second, when binocular data are available, the method does not discard potential monocular microsaccades, or microsaccades with a very small component in one of the eyes (Van Horn & Cullen, 2012), as most previous methods do.…”

Section: Advantages Of the Clustering Methodsmentioning

confidence: 99%