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Kirchner J, Watson T, Bauer J, Lappe M. Eyeball translations affect saccadic eye movements beyond brainstem control. J Neurophysiol 2023; 130:1334-1343. [PMID: 37877201 DOI: 10.1152/jn.00021.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 10/12/2023] [Accepted: 10/17/2023] [Indexed: 10/26/2023] Open
Abstract
Vision requires that we rotate our eyes frequently to look at informative structures in the scene. Eye movements are planned by the brain but their execution depends on the mechanical properties of the oculomotor plant, that is, the arrangement of eyeball position, muscle insertions, and pulley locations. Therefore, the biomechanics of rotations is sensitive to eyeball translation because it changes muscle levers. Eyeball translations are little researched as they are difficult to measure with conventional techniques. Here, we investigated the effects of eyeball translation on the coordination of eyeball rotation by high-speed MRI recordings of saccadic eye movements during blinks, which are known to produce strong translations. We found that saccades during blinks massively overshoot their targets and that these overshoots occur in a transient fashion such that the gaze is back on target at the time the blink ends. These dynamic overshoots were tightly coupled to the eyeball translation, both in time and in size. Saccades made without blinks were also accompanied by small amounts of transient eyeball retraction, the size of which scaled with saccade amplitude. These findings demonstrate a complex combination of rotation and translation of the eye. The mechanical consequences of eyeball translation on oculomotor control should be considered along with the neural implementation in the brainstem to understand the generation of eye movements and their disorders.NEW & NOTEWORTHY We found that saccades during blinks can massively overshoot their target when the eyeball is retracted. Our data imply that the overshoots are not part of the saccade plan prepared in the brainstem, but instead a consequence of the altered biomechanics resulting from concurrent eyeball translation and rotation. To our best knowledge, this is the first direct observation of dynamic properties of the oculomotor plant altering the execution of rotational eye movements.
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Affiliation(s)
- Johannes Kirchner
- Institute for Psychology, University of Münster, Münster, Germany
- Otto-Creutzfeldt Center for Cognitive and Behavioural Neuroscience, University of Münster, Münster, Germany
| | - Tamara Watson
- School of Psychology, Western Sydney University, Penrith, New South Wales, Australia
| | - Jochen Bauer
- Otto-Creutzfeldt Center for Cognitive and Behavioural Neuroscience, University of Münster, Münster, Germany
- Department of Clinical Radiology, University of Münster, Münster, Germany
| | - Markus Lappe
- Institute for Psychology, University of Münster, Münster, Germany
- Otto-Creutzfeldt Center for Cognitive and Behavioural Neuroscience, University of Münster, Münster, Germany
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2
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Bohlen MO, Warren S, May PJ. Is the central mesencephalic reticular formation a purely horizontal gaze center? Brain Struct Funct 2022; 227:2367-2393. [PMID: 35871423 DOI: 10.1007/s00429-022-02532-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 06/30/2022] [Indexed: 01/12/2023]
Abstract
Historically, the central mesencephalic reticular formation has been regarded as a purely horizontal gaze center based on the fact that electrical stimulation of this region produces horizontal saccades, it provides monosynaptic input to medial rectus motoneurons, and cells recorded in this region often display a peak in firing when horizontal saccades are made. We tested the proposition that the central mesencephalic reticular formation is purely a horizontal gaze center by examining whether this region also supplies terminals to superior rectus and levator palpebrae superioris motoneurons, both of which fire when making vertical eye movements. The experiments were carried out using dual tracer techniques at the light and electron microscopic level in macaque monkeys. Injections of biotinylated dextran amine or Phaseolus vulgaris leukoagglutinin into the central mesencephalic reticular formation produced anterogradely labeled terminals that were in synaptic contact with superior rectus and levator palpebrae superioris motoneurons that had been retrogradely labeled. These results indicate that this region is not purely connected with horizontal gaze motoneurons. In addition, we found that the number of contacts on vertical gaze motoneurons increased with more rostral injections involving the mesencephalic reticular formation adjacent to the interstitial nucleus of Cajal. This suggests that there is a caudal to rostral gradient for horizontal to vertical saccades, respectively, represented within the midbrain reticular formation. Finally, we utilized post-embedding immunohistochemistry to show that a portion of the labeled terminals were GABAergic, indicating they likely originate from downgaze premotor neurons.
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Affiliation(s)
- Martin O Bohlen
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Susan Warren
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, 2500 North State St., Jackson, MS, 39216, USA
| | - Paul J May
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, 2500 North State St., Jackson, MS, 39216, USA.
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3
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Kirchner J, Watson TL, Busch NA, Lappe M. Timing and kinematics of horizontal within-blink saccades measured using EOG. J Neurophysiol 2022; 127:1655-1668. [PMID: 35647737 DOI: 10.1152/jn.00076.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Eye blinks are the brief closures of the lid. They are accompanied by a co-contraction of the eye muscles that temporarily pulls the whole eyeball back into its socket. When blinks occur together with execution of saccadic gaze shifts, they interfere with the saccadic premotor circuit, causing these within-blink saccades to be slower than normal and also time-locked to blinks. In order to analyse the trajectory of within-blink saccades, the subtraction of the entangled blink-related eye movement is required. Here we propose a combination of principal component analysis (PCA) and a regression model to subtract the blink-related component of the eye movement based on the respective blink metrics. We used electrooculography (EOG) to measure eye and lid movements of twelve participants who performed saccades with and without blinks. We found that within-blink saccades are slower than without-blink saccades and are tightly coupled in time to blink onset. Surprisingly, in some participants we observed large dynamic overshoots of up to 15° for saccades of only 5° amplitude. This finding challenges the current view that within-blink saccades are programmed as slow, but straight, saccades. We hypothesise that the dynamic overshoots could either be attributed to inhibition of omnipause neurons during blinks, the simultaneous co-contraction of extraocular muscles or a combination of both.
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Affiliation(s)
- Johannes Kirchner
- Institute for Psychology, grid.5949.1University of Münster, Münster, Germany
| | - Tamara Lea Watson
- School of Psychology, The University of Western Sydney, Sydney, Australia
| | - Niko A Busch
- Westfälische Wilhelms-Universität Münster, Münster, Nordrhein-Westfalen, Germany
| | - Markus Lappe
- Otto-Creutzfeldt Center for Cognitive and Behavioural Neuroscience, University of Muenster
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4
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Warren S, May PJ. Macaque monkey trigeminal blink reflex circuits targeting levator palpebrae superioris motoneurons. J Comp Neurol 2021; 529:3389-3409. [PMID: 34101199 DOI: 10.1002/cne.25198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/21/2021] [Accepted: 05/31/2021] [Indexed: 12/18/2022]
Abstract
For normal viewing, the eyes are held open by the tonic actions of the levator palpebrae superioris (levator) muscle raising the upper eyelid. This activity is interrupted during blinks, when the eyelid sweeps down to spread the tear film or protect the cornea. We examined the circuit connecting the principal trigeminal nucleus to the levator motoneurons by use of both anterograde and retrograde tracers in macaque monkeys. Injections of anterograde tracer were made into the principal trigeminal nucleus using either a stereotaxic approach or localization following physiological characterization of trigeminal second order neurons. Anterogradely labeled axonal arbors were located both within the caudal central subdivision, which contains levator motoneurons, and in the adjacent supraoculomotor area. Labeled boutons made synaptic contacts on retrogradely labeled levator motoneurons indicating a monosynaptic connection. As the eye is also retracted through the actions of the rectus muscles during a blink, we examined whether these trigeminal injections labeled boutons contacting rectus motoneurons within the oculomotor nucleus. These were not found when the injection sites were confined to the principal trigeminal nucleus region. To identify the source of the projection to the levator motoneurons, we injected retrograde tracer into the oculomotor complex. Retrogradely labeled cells were confined to a narrow, dorsoventrally oriented cell population that lined the rostral edge of the principal trigeminal nucleus. Presumably these cells inhibit levator motoneurons, while other parts of the trigeminal sensory complex are activating orbicularis oculi motoneurons, when a blink is initiated by sensory stimuli contacting the face.
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Affiliation(s)
- Susan Warren
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Paul J May
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, Mississippi, USA
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Schall JD, Paré M. The unknown but knowable relationship between Presaccadic Accumulation of activity and Saccade initiation. J Comput Neurosci 2021; 49:213-228. [PMID: 33712942 DOI: 10.1007/s10827-021-00784-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 01/06/2021] [Accepted: 02/16/2021] [Indexed: 12/01/2022]
Abstract
The goal of this short review is to call attention to a yawning gap of knowledge that separates two processes essential for saccade production. On the one hand, knowledge about the saccade generation circuitry within the brainstem is detailed and precise - push-pull interactions between gaze-shifting and gaze-holding processes control the time of saccade initiation, which begins when omnipause neurons are inhibited and brainstem burst neurons are excited. On the other hand, knowledge about the cortical and subcortical premotor circuitry accomplishing saccade initiation has crystalized around the concept of stochastic accumulation - the accumulating activity of saccade neurons reaching a fixed value triggers a saccade. Here is the gap: we do not know how the reaching of a threshold by premotor neurons causes the critical pause and burst of brainstem neurons that initiates saccades. Why this problem matters and how it can be addressed will be discussed. Closing the gap would unify two rich but curiously disconnected empirical and theoretical domains.
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Affiliation(s)
- Jeffrey D Schall
- Centre for Vision Research, Vision Science to Application, Department of Biology, York University, Ontario, M3J 1P3, Toronto, Canada.
| | - Martin Paré
- Department of Biomedical & Molecular Sciences and of Psychology, Queen's University, Ontario, ON K7L 3N6, Kingston, Canada
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May PJ, Warren S. Macaque monkey trigeminal blink reflex circuits targeting orbicularis oculi motoneurons. J Comp Neurol 2021; 529:2842-2864. [PMID: 33598920 DOI: 10.1002/cne.25130] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/10/2021] [Accepted: 02/13/2021] [Indexed: 11/10/2022]
Abstract
The trigeminal blink reflex plays an important role in protecting the corneal surface from damage and preserving visual function in an unpredictable environment. The closing phase of the human reflex, produced by activation of the orbicularis oculi (ObOc) muscles, consists of an initial, small, ipsilateral R1 component, followed by a larger, bilateral R2 component. We investigated the circuitry that underlies this reflex in macaque (Macaca fascicularis and Macaca mulatta) monkeys by the use of single and dual tracer methods. Injection of retrograde tracer into the facial nucleus labeled neurons in the principal trigeminal nucleus, and in the spinal nucleus pars oralis and interpolaris, bilaterally, and in pars caudalis, ipsilaterally. Injection of anterograde tracer into the principal trigeminal nucleus labeled axons that directly terminated on ObOc motoneurons, with an ipsilateral predominance. Injection of anterograde tracer into pars caudalis of the spinal trigeminal nucleus labeled axons that directly terminated on ipsilateral ObOc motoneurons. The observed pattern of labeling indicates that the reticular formation ventromedial to the principal and spinal nuclei also contributes extensive bilateral input to ObOc motoneurons. Thus, much of the trigeminal sensory complex is in a position to supply a monosynaptic drive for lid closure, and the adjacent reticular formation can supply a disynaptic drive. These findings indicate that the assignment of the R1 and R2 components of the blink reflex to different parts of the trigeminal sensory complex cannot be exclusively based on subdivision connectional relationships with facial motoneurons. The characteristics of the R2 component may be due, instead, to other circuit properties.
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Affiliation(s)
- Paul J May
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Susan Warren
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, Mississippi, USA
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7
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Murphy AP, Leopold DA. A parameterized digital 3D model of the Rhesus macaque face for investigating the visual processing of social cues. J Neurosci Methods 2019; 324:108309. [PMID: 31229584 PMCID: PMC7446874 DOI: 10.1016/j.jneumeth.2019.06.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 05/31/2019] [Accepted: 06/01/2019] [Indexed: 12/22/2022]
Abstract
BACKGROUND Rhesus macaques are the most popular model species for studying the neural basis of visual face processing and social interaction using intracranial methods. However, the challenge of creating realistic, dynamic, and parametric macaque face stimuli has limited the experimental control and ethological validity of existing approaches. NEW METHOD We performed statistical analyses of in vivo computed tomography data to generate an anatomically accurate, three-dimensional representation of Rhesus macaque cranio-facial morphology. The surface structures were further edited, rigged and textured by a professional digital artist with careful reference to photographs of macaque facial expression, colouration and pelage. RESULTS The model offers precise, continuous, parametric control of craniofacial shape, emotional expression, head orientation, eye gaze direction, and many other parameters that can be adjusted to render either static or dynamic high-resolution faces. Example single-unit responses to such stimuli in macaque inferotemporal cortex demonstrate the value of parametric control over facial appearance and behaviours. COMPARISON WITH EXISTING METHOD(S) The generation of such a high-dimensionality and systematically controlled stimulus set of conspecific faces, with accurate craniofacial modelling and professional finalization of facial details, is currently not achievable using existing methods. CONCLUSIONS The results herald a new set of possibilities in adaptive sampling of a high-dimensional and socially meaningful feature space, thus opening the door to systematic testing of hypotheses about the abundant neural specialization for faces found in the primate.
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Affiliation(s)
- Aidan P Murphy
- Section on Cognitive Neurophysiology and Imaging, NIMH, Bethesda, MD, USA.
| | - David A Leopold
- Section on Cognitive Neurophysiology and Imaging, NIMH, Bethesda, MD, USA
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8
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Jagadisan UK, Gandhi NJ. Removal of inhibition uncovers latent movement potential during preparation. eLife 2017; 6:29648. [PMID: 28891467 PMCID: PMC5650474 DOI: 10.7554/elife.29648] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/08/2017] [Indexed: 12/20/2022] Open
Abstract
The motor system prepares for movements well in advance of their execution. In the gaze control system, the dynamics of preparatory neural activity have been well described by stochastic accumulation-to-threshold models. However, it is unclear whether this activity has features indicative of a hidden movement command. We explicitly tested whether preparatory neural activity in premotor neurons of the primate superior colliculus has 'motor potential'. We removed downstream inhibition on the saccadic system using the trigeminal blink reflex, triggering saccades at earlier-than-normal latencies. Accumulating low-frequency activity was predictive of eye movement dynamics tens of milliseconds in advance of the actual saccade, indicating the presence of a latent movement command. We also show that reaching a fixed threshold level is not a necessary condition for movement initiation. The results bring into question extant models of saccade generation and support the possibility of a concurrent representation for movement preparation and generation.
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Affiliation(s)
- Uday K Jagadisan
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, United States.,Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, United States
| | - Neeraj J Gandhi
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, United States.,Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, United States.,Department of Otolaryngology, University of Pittsburgh, Pittsburgh, United States.,Department of Neuroscience, University of Pittsburgh, Pittsburgh, United States
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9
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Hamedani AG, Gold DR. Eyelid Dysfunction in Neurodegenerative, Neurogenetic, and Neurometabolic Disease. Front Neurol 2017; 8:329. [PMID: 28769865 PMCID: PMC5513921 DOI: 10.3389/fneur.2017.00329] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 06/23/2017] [Indexed: 12/18/2022] Open
Abstract
Eye movement abnormalities are among the earliest clinical manifestations of inherited and acquired neurodegenerative diseases and play an integral role in their diagnosis. Eyelid movement is neuroanatomically linked to eye movement, and thus eyelid dysfunction can also be a distinguishing feature of neurodegenerative disease and complements eye movement abnormalities in helping us to understand their pathophysiology. In this review, we summarize the various eyelid abnormalities that can occur in neurodegenerative, neurogenetic, and neurometabolic diseases. We discuss eyelid disorders, such as ptosis, eyelid retraction, abnormal spontaneous and reflexive blinking, blepharospasm, and eyelid apraxia in the context of the neuroanatomic pathways that are affected. We also review the literature regarding the prevalence of eyelid abnormalities in different neurologic diseases as well as treatment strategies (Table 1).
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Affiliation(s)
- Ali G Hamedani
- Department of Neurology, Hospital of the University of Pennsylvania, Philadelphia, PA, United States
| | - Daniel R Gold
- Department of Neurology, Johns Hopkins Hospital, Baltimore, MD, United States.,Department of Ophthalmology, Johns Hopkins Hospital, Baltimore, MD, United States.,Department of Neurosurgery, Johns Hopkins Hospital, Baltimore, MD, United States.,Department of Otolaryngology - Head and Neck Surgery, Johns Hopkins Hospital, Baltimore, MD, United States
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10
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Disruption of Fixation Reveals Latent Sensorimotor Processes in the Superior Colliculus. J Neurosci 2017; 36:6129-40. [PMID: 27251631 DOI: 10.1523/jneurosci.3685-15.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 04/12/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Executive control of voluntary movements is a hallmark of the mammalian brain. In the gaze-control network, this function is thought to be mediated by a critical balance between neurons responsible for generating movements and those responsible for fixating or suppressing movements, but the nature of this balance between the relevant elements-saccade-generating and fixation-related neurons-remains unclear. Specifically, it has been debated whether the two functions are necessarily coupled (i.e., push-and-pull) or independently controlled. Here we show that behavioral perturbation of ongoing fixation with the trigeminal blink reflex in monkeys (Macaca mulatta) alters the effective balance between fixation and saccade-generating neurons in the superior colliculus (SC) and can lead to premature gaze shifts reminiscent of compromised inhibitory control. The shift in balance is primarily driven by an increase in the activity of visuomovement neurons in the caudal SC, and the extent to which fixation-related neurons in the rostral SC play a role seems to be linked to the animal's propensity to make microsaccades. The perturbation also reveals a hitherto unknown feature of sensorimotor integration: the presence of a hidden visual response in canonical movement neurons. These findings offer new insights into the latent functional interactions, or lack thereof, between components of the gaze-control network, suggesting that the perturbation technique used here may prove to be a useful tool for probing the neural mechanisms of movement generation in executive function and dysfunction. SIGNIFICANCE STATEMENT Eye movements are an integral part of how we explore the environment. Although we know a great deal about where sensorimotor transformations leading to saccadic eye movements are implemented in the brain, less is known about the functional interactions between neurons that maintain gaze fixation and neurons that program saccades. In this study, we used a novel approach to study these interactions. By transient disruption of fixation, we found that activity of saccade-generating neurons can increase independently of modulation in fixation-related neurons, which may occasionally lead to premature movements mimicking lack of impulse control. Our findings support the notion of a common pathway for sensory and movement processing and suggest that impulsive movements arise when sensory processes become "motorized."
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11
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Saccades evoked in response to electrical stimulation of the posterior bank of the arcuate sulcus. Exp Brain Res 2017. [DOI: 10.1007/s00221-017-5012-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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12
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Buonocore A, Chen CY, Tian X, Idrees S, Münch TA, Hafed ZM. Alteration of the microsaccadic velocity-amplitude main sequence relationship after visual transients: implications for models of saccade control. J Neurophysiol 2017; 117:1894-1910. [PMID: 28202573 DOI: 10.1152/jn.00811.2016] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 02/14/2017] [Accepted: 02/14/2017] [Indexed: 11/22/2022] Open
Abstract
Microsaccades occur during gaze fixation to correct for miniscule foveal motor errors. The mechanisms governing such fine oculomotor control are still not fully understood. In this study, we explored microsaccade control by analyzing the impacts of transient visual stimuli on these movements' kinematics. We found that such kinematics can be altered in systematic ways depending on the timing and spatial geometry of visual transients relative to the movement goals. In two male rhesus macaques, we presented peripheral or foveal visual transients during an otherwise stable period of fixation. Such transients resulted in well-known reductions in microsaccade frequency, and our goal was to investigate whether microsaccade kinematics would additionally be altered. We found that both microsaccade timing and amplitude were modulated by the visual transients, and in predictable manners by these transients' timing and geometry. Interestingly, modulations in the peak velocity of the same movements were not proportional to the observed amplitude modulations, suggesting a violation of the well-known "main sequence" relationship between microsaccade amplitude and peak velocity. We hypothesize that visual stimulation during movement preparation affects not only the saccadic "Go" system driving eye movements but also a "Pause" system inhibiting them. If the Pause system happens to be already turned off despite the new visual input, movement kinematics can be altered by the readout of additional visually evoked spikes in the Go system coding for the flash location. Our results demonstrate precise control over individual microscopic saccades and provide testable hypotheses for mechanisms of saccade control in general.NEW & NOTEWORTHY Microsaccadic eye movements play an important role in several aspects of visual perception and cognition. However, the mechanisms for microsaccade control are still not fully understood. We found that microsaccade kinematics can be altered in a systematic manner by visual transients, revealing a previously unappreciated and exquisite level of control by the oculomotor system of even the smallest saccades. Our results suggest precise temporal interaction between visual, motor, and inhibitory signals in microsaccade control.
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Affiliation(s)
- Antimo Buonocore
- Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany; .,Hertie Institute for Clinical Brain Research, Tübingen University, Tübingen, Germany
| | - Chih-Yang Chen
- Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany.,Graduate School of Neural and Behavioural Sciences, International Max Planck Research School, Tübingen University, Tübingen, Germany; and.,Hertie Institute for Clinical Brain Research, Tübingen University, Tübingen, Germany
| | - Xiaoguang Tian
- Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany.,Graduate School of Neural and Behavioural Sciences, International Max Planck Research School, Tübingen University, Tübingen, Germany; and.,Hertie Institute for Clinical Brain Research, Tübingen University, Tübingen, Germany
| | - Saad Idrees
- Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany.,Graduate School of Neural and Behavioural Sciences, International Max Planck Research School, Tübingen University, Tübingen, Germany; and
| | - Thomas A Münch
- Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany
| | - Ziad M Hafed
- Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany.,Hertie Institute for Clinical Brain Research, Tübingen University, Tübingen, Germany
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13
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Busettini C, Frölich MA. Effects of mild to moderate sedation on saccadic eye movements. Behav Brain Res 2014; 272:286-302. [PMID: 25026096 DOI: 10.1016/j.bbr.2014.07.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 07/02/2014] [Accepted: 07/07/2014] [Indexed: 10/25/2022]
Abstract
Sedatives alter the metrics of saccadic eye movements. If these effects are nonspecific consequences of sedation, like drowsiness and loss of attention to the task, or differ between sedatives is still unresolved. A placebo-controlled multi-step infusion of one of three sedatives, propofol or midazolam, both GABA-A agonists, or dexmedetedomidine, an α2-adrenergic agonist, was adopted to compare the effects of these three drugs in exactly the same experimental conditions. 60 healthy human volunteers, randomly divided in 4 groups, participated in the study. Each infusion step, delivered by a computer-controlled infusion pump, lasted 20min. During the last 10min of each step, the subject executed a saccadic task. Target concentration was doubled at each step. This block was repeated until the subject was too sedated to continue or for a maximum of 6 blocks. Subjects were unaware which infusion they were receiving. A video eye tracker was used to record the movements of the right eye. Saccadic parameters were modeled as a function of block number, estimated sedative plasma concentration, and subjective evaluation of sedation. Propofol and midazolam had strong effects on the dynamics and latency of the saccades. Midazolam, and to a less extent, propofol, caused saccades to become increasingly hypometric. Dexmedetedomidine had less impact on saccadic metrics and presented no changes in saccadic gain. Suppression of the sympathetic system associated with dexmedetomidine has different effects on eye movements from the increased activity of the inhibitory GABA-A receptors by propofol and midazolam even when the subjects reported similar sedation level.
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Affiliation(s)
- C Busettini
- Department of Vision Sciences and Vision Science Research Center, University of Alabama at Birmingham, Birmingham, AL 35294-4390, USA.
| | - M A Frölich
- Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, AL 35294-6810, USA
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14
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Wang N, Perkins E, Zhou L, Warren S, May PJ. Anatomical evidence that the superior colliculus controls saccades through central mesencephalic reticular formation gating of omnipause neuron activity. J Neurosci 2013; 33:16285-96. [PMID: 24107960 PMCID: PMC3792464 DOI: 10.1523/jneurosci.2726-11.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 07/16/2013] [Accepted: 08/29/2013] [Indexed: 11/21/2022] Open
Abstract
Omnipause neurons (OPNs) within the nucleus raphe interpositus (RIP) help gate the transition between fixation and saccadic eye movements by monosynaptically suppressing activity in premotor burst neurons during fixation, and releasing them during saccades. Premotor neuron activity is initiated by excitatory input from the superior colliculus (SC), but how the tectum's saccade-related activity turns off OPNs is not known. Since the central mesencephalic reticular formation (cMRF) is a major SC target, we explored whether this nucleus has the appropriate connections to support tectal gating of OPN activity. In dual-tracer experiments undertaken in macaque monkeys (Macaca fascicularis), cMRF neurons labeled retrogradely from injections into RIP had numerous anterogradely labeled terminals closely associated with them following SC injections. This suggested the presence of an SC-cMRF-RIP pathway. Furthermore, anterograde tracers injected into the cMRF of other macaques labeled axonal terminals in RIP, confirming this cMRF projection. To determine whether the cMRF projections gate OPN activity, postembedding electron microscopic immunochemistry was performed on anterogradely labeled cMRF terminals with antibody to GABA or glycine. Of the terminals analyzed, 51.4% were GABA positive, 35.5% were GABA negative, and most contacted glycinergic cells. In summary, a trans-cMRF pathway connecting the SC to the RIP is present. This pathway contains inhibitory elements that could help gate omnipause activity and allow other tectal drives to induce the bursts of firing in premotor neurons that are necessary for saccades. The non-GABAergic cMRF terminals may derive from fixation units in the cMRF.
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Affiliation(s)
- Niping Wang
- Departments of Neurobiology and Anatomical Sciences
- Periodontics and Preventive Sciences
| | - Eddie Perkins
- Departments of Neurobiology and Anatomical Sciences
- Neurosurgery
| | | | - Susan Warren
- Departments of Neurobiology and Anatomical Sciences
| | - Paul J. May
- Departments of Neurobiology and Anatomical Sciences
- Neurology, and
- Ophthalmology, University of Mississippi Medical Center, Jackson, Mississippi 39216
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Katnani HA, Van Opstal AJ, Gandhi NJ. Blink perturbation effects on saccades evoked by microstimulation of the superior colliculus. PLoS One 2012; 7:e51843. [PMID: 23251639 PMCID: PMC3522602 DOI: 10.1371/journal.pone.0051843] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 11/07/2012] [Indexed: 11/19/2022] Open
Abstract
Current knowledge of saccade-blink interactions suggests that blinks have paradoxical effects on saccade generation. Blinks suppress saccade generation by attenuating the oculomotor drive command in structures like the superior colliculus (SC), but they also disinhibit the saccadic system by removing the potent inhibition of pontine omnipause neurons (OPNs). To better characterize these effects, we evoked the trigeminal blink reflex by delivering an air puff to one eye as saccades were evoked by sub-optimal stimulation of the SC. For every stimulation site, the peak and average velocities of stimulation with blink movements (SwBMs) were lower than stimulation-only saccades (SoMs), supporting the notion that the oculomotor drive is weakened in the presence of a blink. In contrast, the duration of the SwBMs was longer, consistent with the hypothesis that the blink-induced inhibition of the OPNs could prolong the window of time available for oculomotor commands to drive an eye movement. The amplitude of the SwBM could also be larger than the SoM amplitude obtained from the same site, particularly for cases in which blink-associated eye movements exhibited the slowest kinematics. The results are interpreted in terms of neural signatures of saccade-blink interactions.
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Affiliation(s)
- Husam A Katnani
- Department of Bioengineering, University of Pittsburgh, Pennsylvania, USA.
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16
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May PJ, Vidal PP, Baker H, Baker R. Physiological and anatomical evidence for an inhibitory trigemino-oculomotor pathway in the cat. J Comp Neurol 2012; 520:2218-40. [PMID: 22237697 PMCID: PMC3885353 DOI: 10.1002/cne.23039] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
During blink down-phase, the levator palpebrae superioris (levator) muscle is inactivated, allowing the orbicularis oculi muscle to act. For trigeminal reflex blinks, the excitatory connections from trigeminal sensory nuclei to the facial nucleus have been described, but the pathway whereby the levator is turned off have not. We examined this question by use of both physiological and anatomical approaches in the cat. Intracellular records from antidromically activated levator motoneurons revealed that periorbital electrical stimulation produced bilateral, long latency inhibitory postsynaptic potentials (IPSPs). Central electrical stimulation of the principal trigeminal nucleus produced shorter latency IPSPs. Intracellular staining revealed that these motoneurons reside in the caudal central subdivision and have 10 or more poorly branched dendrites, which extend bilaterally into the surrounding supraoculomotor area. Axons penetrated in this region could be activated from periorbital and central electrodes. Neurons labeled from tracer injections into the caudal oculomotor complex were distributed in a crescent-shaped band that lined the ventral and rostral aspects of the pontine trigeminal sensory nucleus. Double-label immunohistochemical procedures demonstrated that these cells were not tyrosine hydroxylase-positive cells in the Kölliker-Fuse area. Instead, supraorbital nerve afferents displayed a similar crescent-shaped distribution, suggesting they drive these trigemino-oculomotor neurons. Anterograde labeling of the trigemino-oculomotor projection indicates that it terminates bilaterally, in and above the caudal central subdivision. These results characterize a trigemino-oculomotor pathway that inhibits levator palpebrae motoneurons in response to blink-producing periorbital stimuli. The bilateral distributions of trigemino-oculomotor afferents, levator motoneurons, and their dendrites supply a morphological basis for conjugate lid movements.
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Affiliation(s)
- Paul J May
- Department of Neurobiology and Anatomical Sciences, Departments of Ophthalmology and Neurology, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA.
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Interactions between gaze-evoked blinks and gaze shifts in monkeys. Exp Brain Res 2011; 216:321-39. [PMID: 22083094 DOI: 10.1007/s00221-011-2937-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 10/31/2011] [Indexed: 10/15/2022]
Abstract
Rapid eyelid closure, or a blink, often accompanies head-restrained and head-unrestrained gaze shifts. This study examines the interactions between such gaze-evoked blinks and gaze shifts in monkeys. Blink probability increases with gaze amplitude and at a faster rate for head-unrestrained movements. Across animals, blink likelihood is inversely correlated with the average gaze velocity of large-amplitude control movements. Gaze-evoked blinks induce robust perturbations in eye velocity. Peak and average velocities are reduced, duration is increased, but accuracy is preserved. The temporal features of the perturbation depend on factors such as the time of blink relative to gaze onset, inherent velocity kinematics of control movements, and perhaps initial eye-in-head position. Although variable across animals, the initial effect is a reduction in eye velocity, followed by a reacceleration that yields two or more peaks in its waveform. Interestingly, head velocity is not attenuated; instead, it peaks slightly later and with a larger magnitude. Gaze latency is slightly reduced on trials with gaze-evoked blinks, although the effect was more variable during head-unrestrained movements; no reduction in head latency is observed. Preliminary data also demonstrate a similar perturbation of gaze-evoked blinks during vertical saccades. The results are compared with previously reported effects of reflexive blinks (evoked by air-puff delivered to one eye or supraorbital nerve stimulation) and discussed in terms of effects of blinks on saccadic suppression, neural correlates of the altered eye velocity signals, and implications on the hypothesis that the attenuation in eye velocity is produced by a head movement command.
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