The Brain Stem Saccadic Burst Generator Encodes Gaze in Three-Dimensional Space

Horn, Marion R. Van; Sylvestre, Pierre A.; Cullen, Kathleen E.

doi:10.1152/jn.01379.2007

Cited by 40 publications

(55 citation statements)

References 79 publications

(120 reference statements)

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“…Finally, to compare our sample of SBNs to those previously described Van Horn et al 2008) neurons were also characterized during horizontal saccades combined with vergence (i.e., horizontal disconjugate saccades). The paradigms to elicit horizontal disconjugate saccades have been described previously Sylvestre et al 2003;Van Horn et al 2008).…”

Section: Behavioral Paradigmsmentioning

confidence: 99%

“…The paradigms to elicit horizontal disconjugate saccades have been described previously Sylvestre et al 2003;Van Horn et al 2008). Briefly, an illuminated target changed from one of the close midsagittal LEDs to an eccentric (i.e., right or left of the midsagittal plane) laser target.…”

Section: Behavioral Paradigmsmentioning

confidence: 99%

“…Two general classes of models have been proposed to account for the facilitation of vergence during disconjugate saccades (Busettini and Mays 2005b;Gamlin 2002;King and Zhou 2002;Kumar et al 2006;Mays 1998;Mays and Gamlin 1995;Scudder et al 2002;Van Horn et al 2008;Zhou and King 1998). In one model, the premotor saccadic pathway drives the conjugate component of the saccade, whereas changes in vergence are exclusively driven by a premotor command from vergence neurons.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic Coding of Vertical Facilitated Vergence by Premotor Saccadic Burst Neurons

Horn

Cullen

2008

Journal of Neurophysiology

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Van Horn MR, Cullen KE. Dynamic coding of vertical facilitated vergence by premotor saccadic burst neurons. J Neurophysiol 100: 1967-1982. First published July 23, 2008 doi:10.1152/jn.90580.2008. To redirect our gaze in three-dimensional space we frequently combine saccades and vergence. These eye movements, known as disconjugate saccades, are characterized by eyes rotating by different amounts, with markedly different dynamics, and occur whenever gaze is shifted between near and far objects. How the brain ensures the precise control of binocular positioning remains controversial. It has been proposed that the traditionally assumed "conjugate" saccadic premotor pathway does not encode conjugate commands but rather encodes monocular commands for the right or left eye during saccades. Here, we directly test this proposal by recording from the premotor neurons of the horizontal saccade generator during a dissociation task that required a vergence but no horizontal conjugate saccadic command. Specifically, saccadic burst neurons (SBNs) in the paramedian pontine reticular formation were recorded while rhesus monkeys made vertical saccades made between near and far targets. During this task, we first show that peak vergence velocities were enhanced to saccade-like speeds (e.g., Ͼ150 vs. Ͻ100°/s during saccade-free movements for comparable changes in vergence angle). We then quantified the discharge dynamics of SBNs during these movements and found that the majority of the neurons preferentially encode the velocity of the ipsilateral eye. Notably, a given neuron typically encoded the movement of the same eye during horizontal saccades that were made in depth. Taken together, our findings demonstrate that the brain stem saccadic burst generator encodes integrated conjugate and vergence commands, thus providing strong evidence for the proposal that the classic saccadic premotor pathway controls gaze in three-dimensional space. I N T R O D U C T I O NTo quickly and accurately redirect our gaze between near and far targets, we typically combine saccadic and vergence eye movements. During such eye movements, termed disconjugate saccades, the eyes rotate by different angles and with different trajectories to precisely realign the two visual axes on the new target of interest. Traditionally, disconjugate saccades were thought to be controlled by linear summation of premotor commands from two distinct neural control pathways that separately encode the conjugate and vergence components of eye motion: 1) a conjugate saccadic subsystem, which commands a rapid but yoked movement of the two eyes in a given direction; and 2) a separate vergence subsystem, which rotates the eyes in opposite directions to ensure accurate binocular positioning (Hering 1977; Mays 1984Mays , 1998. Accordingly, the premotor circuitry involved in generating horizontal saccades (e.g., the saccadic burst neurons [SBNs] of the paramedian pontine reticular formation [PPRF]) was generally assumed to provide the command to drive the horizontal conjugate compone...

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Section: Behavioral Paradigmsmentioning

confidence: 99%

Section: Behavioral Paradigmsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamic Coding of Vertical Facilitated Vergence by Premotor Saccadic Burst Neurons

Horn

Cullen

2008

Journal of Neurophysiology

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“…They can also relay signals, for example, to trunk muscles for coordinated eye-head-body movements or to shoulder muscles for coordinated eye-hand movements. It also doesn't matter whether the neurons encode monocular or binocular movements (Zhou and King 1998) or in fronto-parallel or all three dimensions (Van Horn et al 2008). The only requirement is that the putative burst neurons project at least to the abducens motoneurons and discharge for every movement that includes a horizontal ocular saccade component.…”

Section: Assumptions About the Oculomotor Inputmentioning

confidence: 99%

Matching the Oculomotor Drive During Head-Restrained and Head-Unrestrained Gaze Shifts in Monkey

Bechara

Gandhi

2010

Journal of Neurophysiology

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Bechara BP, Gandhi NJ. Matching the oculomotor drive during head-restrained and head-unrestrained gaze shifts in monkey. J Neurophysiol 104: 811-828, 2010. First published May 26, 2010 doi:10.1152/jn.01114.2009. High-frequency burst neurons in the pons provide the eye velocity command (equivalently, the primary oculomotor drive) to the abducens nucleus for generation of the horizontal component of both head-restrained (HR) and head-unrestrained (HU) gaze shifts. We sought to characterize how gaze and its eye-in-head component differ when an "identical" oculomotor drive is used to produce HR and HU movements. To address this objective, the activities of pontine burst neurons were recorded during horizontal HR and HU gaze shifts. The burst profile recorded on each HU trial was compared with the burst waveform of every HR trial obtained for the same neuron. The oculomotor drive was assumed to be comparable for the pair yielding the lowest root-mean-squared error. For matched pairs of HR and HU trials, the peak eye-in-head velocity was substantially smaller in the HU condition, and the reduction was usually greater than the peak head velocity of the HU trial. A time-varying attenuation index, defined as the difference in HR and HU eye velocity waveforms divided by head velocity [␣ ϭ (Ḣ hr Ϫ Ė hu )/Ḣ ] was computed. The index was variable at the onset of the gaze shift, but it settled at values several times greater than 1. The index then decreased gradually during the movement and stabilized at 1 around the end of gaze shift. These results imply that substantial attenuation in eye velocity occurs, at least partially, downstream of the burst neurons. We speculate on the potential roles of burst-tonic neurons in the neural integrator and various cell types in the vestibular nuclei in mediating the attenuation in eye velocity in the presence of head movements. I N T R O D U C T I O NTo align the visual axis on an object of interest, one must shift the line of sight (gaze) by rapidly moving the eyes in their orbits. For large changes in gaze, a head movement typically accompanies the eye-in-head rotation. Such rapid, coordinated movements of the eyes in the orbits and the head in space are termed head-unrestrained (HU) gaze shifts. For smaller changes in gaze or when the head is immobilized, redirections of the visual axis are executed by eye movements within the orbits. We refer to such high-velocity movements as head-restrained (HR) gaze shifts or saccades.The primary oculomotor drive that produces a saccadic rotation of the eyes in orbits is an eye velocity command from neurons in the saccadic burst generator (Robinson 1975). For horizontal eye movements, the eye velocity command is encoded as a high-frequency volley of action potentials by putative short-lead burst neurons (Van Gisbergen et al. 1981) that reside in the paramedian pontine reticular formation (PPRF) and project directly to the abducens motoneurons (Langer et al. 1986;Strassman et al. 1986a). When the head is restrained, properties of the burst specif...

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“…Some of this neurological research focuses on the nature of eye movements, including saccades (ballistic eye movements that jump from location to location in a visual scene in a matter of milliseconds) [15,17]. Some studies [12] closely examine vestibulo-ocular (VOR) reflex in saccadic and slow phase components of gaze shifts.…”

Section: Introduction and Related Workmentioning

confidence: 99%

Modeling Gaze Behavior for Virtual Demonstrators

Huang

Matthews

Matlock

et al. 2011

Intelligent Virtual Agents

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Abstract. Achieving autonomous virtual humans with coherent and natural motions is key for being effective in many educational, training and therapeutic applications. Among several aspects to be considered, the gaze behavior is an important non-verbal communication channel that plays a vital role in the effectiveness of the obtained animations. This paper focuses on analyzing gaze behavior in demonstrative tasks involving arbitrary locations for target objects and listeners. Our analysis is based on full-body motions captured from human participants performing real demonstrative tasks in varied situations. We address temporal information and coordination with targets and observers at varied positions.

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The Brain Stem Saccadic Burst Generator Encodes Gaze in Three-Dimensional Space

Cited by 40 publications

References 79 publications

Dynamic Coding of Vertical Facilitated Vergence by Premotor Saccadic Burst Neurons

Dynamic Coding of Vertical Facilitated Vergence by Premotor Saccadic Burst Neurons

Matching the Oculomotor Drive During Head-Restrained and Head-Unrestrained Gaze Shifts in Monkey

Modeling Gaze Behavior for Virtual Demonstrators

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