Comparison of Saccades Perturbed by Stimulation of the Rostral Superior Colliculus, the Caudal Superior Colliculus, and the Omnipause Neuron Region

Gandhi, Neeraj J.; Keller, Edward L.

doi:10.1152/jn.1999.82.6.3236

Cited by 89 publications

(73 citation statements)

References 71 publications

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“…Below, we discuss how these findings lead to reconsider the functional scheme that is commonly proposed to explain how the brain generates saccades toward a moving target (Optican, 2009). Previous studies have tested the robustness of gaze saccades toward a static target and shown that the orienting system compensates for changes in gaze position induced by a brief electrical stimulation within oculomotor regions like the dSC (Schiller and Sandell, 1983;Sparks and Mays, 1983;Pélisson et al, 1989Pélisson et al, , 1995Gandhi and Keller, 1999), the paramedian pontine reticular formation (Sparks et al, 1987), or the nucleus raphe interpositus (Paré and Guitton, 1998;Gandhi and Keller, 1999;Gandhi and Sparks, 2007). The numerous examples of unchanged accuracy between unperturbed and perturbed saccades reported in our study (Figs.…”

Section: Discussionsupporting

confidence: 57%

Saccadic Interception of a Moving Visual Target after a Spatiotemporal Perturbation

Filippi¹,

Goffart²

2012

J. Neurosci.

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Animals can make saccadic eye movements to intercept a moving object at the right place and time. Such interceptive saccades indicate that, despite variable sensorimotor delays, the brain is able to estimate the current spatiotemporal (hic et nunc) coordinates of a target at saccade end. The present work further tests the robustness of this estimate in the monkey when a change in eye position and a delay are experimentally added before the onset of the saccade and in the absence of visual feedback. These perturbations are induced by brief microstimulation in the deep superior colliculus (dSC). When the microstimulation moves the eyes in the direction opposite to the target motion, a correction saccade brings gaze back on the target path or very near. When it moves the eye in the same direction, the performance is more variable and depends on the stimulated sites. Saccades fall ahead of the target with an error that increases when the stimulation is applied more caudally in the dSC. The numerous cases of compensation indicate that the brain is able to maintain an accurate and robust estimate of the location of the moving target. The inaccuracies observed when stimulating the dSC that encodes the visual field traversed by the target indicate that dSC microstimulation can interfere with signals encoding the target motion path. The results are discussed within the framework of the dual-drive and the remapping hypotheses.

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Section: Discussionsupporting

confidence: 57%

Saccadic Interception of a Moving Visual Target after a Spatiotemporal Perturbation

Filippi¹,

Goffart²

2012

J. Neurosci.

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“…An important feature of the superior colliculus is its subdivision in two functionally distinct regions. The rostral colliculus contains neurons that discharge when a stimulus in the central $2 of the visual field is actively fixated (Munoz and Wurtz, 1992;1993b;Gandhi and Keller, 1999), while neurons in the caudal colliculus show activity related to the preparation and execution of saccades (Dorris et al, 1997). In patients with neglect following a right cortical lesion, a functionally disinhibited left colliculus would exhibit increased fixational activity in its rostral region and increased saccade-related activity in its caudal region.…”

Section: Discussionmentioning

confidence: 99%

“…Second, a distracter presented simultaneously with the target, but in the opposite hemifield, systematically increases saccade latency, which has been termed the remote distracter effect (Walker et al, 1995(Walker et al, , 1997. Both effects are specific to eye movements and have been attributed to inhibitory interactions within the oculomotor system, in particular the superior colliculus Wurtz, 1992, 1993b;Walker et al, 1997;Gandhi and Keller, 1999). Interestingly, a classic hypothesis has related the lateral orienting bias that characterizes spatial neglect to a loss of balance between the neocortex and the superior colliculus (Sprague, 1966).…”

Section: Introductionmentioning

confidence: 99%

A non-spatial bias favouring fixated stimuli revealed in patients with spatial neglect

Ptak

Schnider

Golay

et al. 2007

Brain

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The cardinal feature of spatial neglect is severely impaired exploration of the contralesional space, a failure resulting in unawareness of many contralesional stimuli. This deficit is exacerbated by a reflexive attentional bias toward ipsilesional items. Here we show that, in addition to these spatially lateralized failures, neglect patients also exhibit a severe bias favouring stimuli presented at fixation. We tested neglect patients and matched healthy and right-hemisphere damaged patients without neglect in a task requiring saccade execution to targets in the left or right hemifield. Targets were presented alone or simultaneously with a distracter that appeared in the same hemifield, in the opposite hemifield, or at fixation. We found two fundamental biases in saccade initiation of neglect patients: irrelevant distracters presented in the preserved hemifield tended to capture gaze reflexively, resulting in a large number of saccades erroneously directed toward the distracter. Additionally, distracters presented at fixation severely disrupted saccade initiation irrespective of saccade direction, leading to disproportionately increased latencies of left and right saccades. This latency increase was specific to oculomotor responses of neglect patients and was not observed when a manual response was required. These results show that, in addition to their failure to inhibit reflexive glances toward ipsilesional items neglect patients exhibit a strong oculomotor bias favouring fixated stimuli. We conclude that impaired initiation of saccades in any direction contributes to the deficits of spatial exploration that characterize spatial neglect.

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“…SN pause firing during fixations while producing bursts of spikes prior to and during saccades directed to their response field (Sparks et al 1976;Wurtz and Goldberg 1972;Munoz and Wurtz 1995a). Converging data from microstimulation studies (Gandhi and Keller 1999;Robinson 1972) and single cell recordings (Krauzlis et al 1997;Wurtz 1993a, 1995b) reveal that FN like SN still possess a movement field, i.e., activity of FN is associated with small contraversive saccades. 3 It is not known whether microsaccades that occur involuntarily during fixation originate in the rostral pole of the SC as proposed by Gandhi and Keller (1999) and Munoz et al (2000).…”

Section: Prolongation Of Saccade Latencies Following Microsaccadesmentioning

confidence: 99%

“…Converging data from microstimulation studies (Gandhi and Keller 1999;Robinson 1972) and single cell recordings (Krauzlis et al 1997;Wurtz 1993a, 1995b) reveal that FN like SN still possess a movement field, i.e., activity of FN is associated with small contraversive saccades. 3 It is not known whether microsaccades that occur involuntarily during fixation originate in the rostral pole of the SC as proposed by Gandhi and Keller (1999) and Munoz et al (2000). Our findings that there is a drop of microsaccade rate prior to saccades and an increase of SRTs in both memory and visual trials when microsaccades occurred around the time of the go signal are consistent with this explanation.…”

Section: Prolongation Of Saccade Latencies Following Microsaccadesmentioning

confidence: 99%

Shortening and prolongation of saccade latencies following microsaccades

2005

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When the eyes fixate at a point in a visual scene, small saccades rapidly shift the image on the retina. The effect of these microsaccades on the latency of subsequent large-scale saccades may be twofold. First, microsaccades are associated with an enhancement of visual perception.Their occurrence during saccade target perception should, thus, decrease saccade latencies. On the other hand, microsaccades likely indicate activity in fixation-related oculomotor neurons. These represent competitors to saccade-related cells in the interplay of gaze holding and shifting.Consequently, an increase in saccade latencies after microsaccades would be expected. Here, we present evidence for both aspects of microsaccadic impact on saccade latency. In a delayed response task, participants made saccades to visible or memorized targets. First, microsaccade occurrence up to 50 ms before target disappearance correlated with 18 ms (or 8%) faster saccades to memorized targets. Second, if microsaccades occurred shortly (i.e., < 150 ms) before a saccade was required, saccadic reaction times in visual and memory trials were increased by about 40 ms (or 16%). Hence, microsaccades can have opposite consequences for saccade latencies, pointing at a differential role of these fixational eye movements in preparation of motor programs.

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Comparison of Saccades Perturbed by Stimulation of the Rostral Superior Colliculus, the Caudal Superior Colliculus, and the Omnipause Neuron Region

Cited by 89 publications

References 71 publications

Saccadic Interception of a Moving Visual Target after a Spatiotemporal Perturbation

Saccadic Interception of a Moving Visual Target after a Spatiotemporal Perturbation

A non-spatial bias favouring fixated stimuli revealed in patients with spatial neglect

Shortening and prolongation of saccade latencies following microsaccades

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