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Manzari L, Graziano D, Tramontano M. The Different Stages of Vestibular Neuritis from the Point of View of the Video Head Impulse Test. Audiol Res 2020; 10:31-38. [PMID: 33704148 PMCID: PMC7768365 DOI: 10.4081/audiores.2020.248] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Accepted: 09/22/2019] [Indexed: 11/22/2022] Open
Abstract
Vestibular neuritis (VN) is one of the most common causes of acute vestibular syndrome (AVS). Quantifying the vestibulo-ocular reflex (VOR) gain by the video Head Impulse Test (vHIT) could provide useful information to diagnose VN. This study aims to retrospectively evaluate the VOR gain values during the acute and subacute stages of the VN and to correlate these values with the patients’ dizziness-related handicap. Medical record of 28 patients with VN were reviewed. Patients were assigned to two groups according to the time since the acute vestibular syndrome (AVS). One group with patients assessed within seventy-two hours since the AVS (AVSg) and one group with patients evaluated from four days to six weeks since the AVS (PAVSg). VOR gain was evaluated in all selected patients and correlated to Dizziness Handicap Inventory (DHI). Significant differences were found in the between-subjects analysis in DHI score (p = 0.000) and in the ipsilesional hVOR gain values (p = 0.001). The correlation analysis showed significant results (p = 0.017) between DHI score (40 ± 16.08) and ipsilesional VOR gain (0.54 ± 0.09) in the PAVSg. Patients evaluated within 72 h since the AVS showed anticompensatory saccades (AcS) turning the head toward the contralesional side. Patients with unilateral Superior VN (SVN) could have dissimilar hVOR gain values and DHI score according to the damage of the VIII pair of cranial nerves. AcS in the contralesional side is a sign of acute phase in patients with unilateral SVN.
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Separate and overlapping functional roles for efference copies in the human thalamus. Neuropsychologia 2020; 147:107558. [PMID: 32771475 DOI: 10.1016/j.neuropsychologia.2020.107558] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 11/21/2022]
Abstract
How the perception of space is generated from the multiple maps in the brain is still an unsolved mystery in neuroscience. A neural pathway ascending from the superior colliculus through the medio-dorsal (MD) nucleus of thalamus to the frontal eye field has been identified in monkeys that conveys efference copy information about the metrics of upcoming eye movements. Information sent through this pathway stabilizes vision across saccades. We investigated whether this motor plan information might also shape spatial perception even when no saccades are performed. We studied patients with medial or lateral thalamic lesions (likely involving either the MD or the ventrolateral (VL) nuclei). Patients performed a double-step task testing motor updating, a trans-saccadic localization task testing visual updating, and a localization task during fixation testing a general role of motor signals for visual space in the absence of eye movements. Single patients with medial or lateral thalamic lesions showed deficits in the double-step task, reflecting insufficient transfer of efference copy. However, only a patient with a medial lesion showed impaired performance in the trans-saccadic localization task, suggesting that different types of efference copies contribute to motor and visual updating. During fixation, the MD patient localized stationary stimuli more accurately than healthy controls, suggesting that patients compensate the deficit in visual prediction of saccades - induced by the thalamic lesion - by relying on stationary visual references. We conclude that partially separable efference copy signals contribute to motor and visual stability in company of purely visual signals that are equally effective in supporting trans-saccadic perception.
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Sendhilnathan N, Basu D, Murthy A. Assessing within-trial and across-trial neural variability in macaque frontal eye fields and their relation to behaviour. Eur J Neurosci 2020; 52:4267-4282. [PMID: 32542865 DOI: 10.1111/ejn.14864] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 06/02/2020] [Accepted: 06/03/2020] [Indexed: 11/29/2022]
Abstract
The conventional approach to understanding neural responses underlying complex computations is to study across-trial averages of repeatedly performed computations from single neurons. When neurons perform complex computations, such as processing stimulus-related information or movement planning, it has been repeatedly shown, through measures such as the Fano factor (FF), that neural variability across trials decreases. However, multiple neurons contribute to a common computation on a single trial, rather than a single neuron contributing to a computation across multiple trials. Therefore, at the level of a single trial, the concept of FF loses significance. Here, using a combination of simulations and empirical data, we show that changes in the spiking regularity on single trials produce changes in FF. Further, at the behavioural level, the reaction time of the animal was faster when the neural spiking regularity both within and across trials was lower. Taken together, our results provide further constraints on how changes in spiking statistics help neurons optimally encode visual and saccade-related information across multiple timescales and its implication on behaviour.
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Ishrat M, Abrol P. Image complexity analysis with scanpath identification using remote gaze estimation model. MULTIMEDIA TOOLS AND APPLICATIONS 2020; 79:24393-24412. [PMID: 32837248 PMCID: PMC7305931 DOI: 10.1007/s11042-020-09117-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/20/2020] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
Analysis of gaze points has been a vital tool for understanding varied human behavioral pattern and underlying psychological processing. Gaze points are analyzed generally in terms of two events of fixations and saccades that are collectively termed as scanpath. Scanpath could potentially establish correlation between visual scenery and human cognitive tendencies. Scanpath has been analyzed for different domains that include visual perception, usability, memory, visual search or low level attributes like color, illumination and edges in an image. Visual search is one prominent area that examines scanpath of subjects while a target object is searched in a given set of images. Visual search explores behavioral tendencies of subjects with respect to image complexity. Complexity of an image is governed by spatial, frequency and color information present in the image. Scanpath based image complexity analysis determines human visual behavior that could lead to development of interactive and intelligent systems. There are several sophisticated eye tracking devices and associated algorithms for recording and classification of scanpath. However, in the present scenario when the chances of viral infections (COVID-19) from known and unknown sources are high, it is very important that the contact less methods and models be designed. In addition, even though the devices acquire and process eye movement data with fair accuracy but are intrusive and costly. The objective of current research work is to establish the complexity of the given set of images while target objects are searched and to present analysis of gaze search pattern. To achieve these objectives a remote gaze estimation and analysis model has been proposed for scanpath identification and analysis. The model is an alternate option for gaze point tracking and scanpath analysis that is non intrusive and low cost. The gaze points are tracked remotely as against sophisticated wearable eye tracking devices available in the market. The model employs easily available softwares and hardware devices. In the current work, complexity is derived on the basis of analysis of fixation and saccade gaze points. Based on the results generated by the proposed model, influence on subjects due to external stimuli is studied. The set of images chosen, act as external stimuli for the subjects during visual search. In order to statistically analyze scanpath for different subjects, certain scanpath parameters have been identified. The model maps and classifies eye movement gaze points into fixations and saccades and generates data for identified parameters. For eye detection and subsequent iris detection voila jones and circular hough transform (CHT) algorithms have been used. Identification by dispersion threshold (I-DT) is implemented for scanpath identification. The algorithms are customized for better iris and scanpath detection. Algorithms are developed for gaze screen mapping and classification of fixations and saccades. The experimentation has been carried on different subjects. Variations during visual search have been observed and analyzed. The present model requires no contact of human subject with any equipment including eye tracking devices, screen or computing devices.
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Suppression Head Impulse Paradigm (SHIMP) in evaluating the vestibulo-saccadic interaction in patients with vestibular neuritis. Eur Arch Otorhinolaryngol 2020; 277:3205-3212. [PMID: 32472160 DOI: 10.1007/s00405-020-06085-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 05/22/2020] [Indexed: 10/24/2022]
Abstract
PURPOSE Evaluate the potential clinical application of the Suppression Head Impulse Paradigm (SHIMP) in evaluating the vestibulo-saccadic interaction in patients with vestibular neuritis (VN). METHODS A retrospective study was performed. Fifteen patients diagnosed with unilateral VN were identified from a database of ENT vestibular clinic from January 2011 to February 2020. Medical records were reviewed to determine clinical presentation, vestibular testing results, treatment, and recovery. RESULTS Fifteen patients (7 left ear, 8 right ear, mean age 58.73 ± 10.73, six female) met the inclusion criteria and were enrolled in the study. Significant differences were found in the within-subjects analysis at T1 in DHI score (p = 0.001), VOR gain (p < 0.005), and in the percentages of impulses containing a SHIMPs saccade when the head is passively turned toward the affected side (p = 0.001). CONCLUSIONS SHIMPs paradigm provides useful information about the value of vestibulo-saccadic interaction as new recovery strategies in patients with VN.
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Salem W, Cellini B, Frye MA, Mongeau JM. Fly eyes are not still: a motion illusion in Drosophila flight supports parallel visual processing. J Exp Biol 2020; 223:jeb212316. [PMID: 32321749 PMCID: PMC7272343 DOI: 10.1242/jeb.212316] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 04/12/2020] [Indexed: 02/05/2023]
Abstract
Most animals shift gaze by a 'fixate and saccade' strategy, where the fixation phase stabilizes background motion. A logical prerequisite for robust detection and tracking of moving foreground objects, therefore, is to suppress the perception of background motion. In a virtual reality magnetic tether system enabling free yaw movement, Drosophila implemented a fixate and saccade strategy in the presence of a static panorama. When the spatial wavelength of a vertical grating was below the Nyquist wavelength of the compound eyes, flies drifted continuously and gaze could not be maintained at a single location. Because the drift occurs from a motionless stimulus - thus any perceived motion stimuli are generated by the fly itself - it is illusory, driven by perceptual aliasing. Notably, the drift speed was significantly faster than under a uniform panorama, suggesting perceptual enhancement as a result of aliasing. Under the same visual conditions in a rigid-tether paradigm, wing steering responses to the unresolvable static panorama were not distinguishable from those to a resolvable static pattern, suggesting visual aliasing is induced by ego motion. We hypothesized that obstructing the control of gaze fixation also disrupts detection and tracking of objects. Using the illusory motion stimulus, we show that magnetically tethered Drosophila track objects robustly in flight even when gaze is not fixated as flies continuously drift. Taken together, our study provides further support for parallel visual motion processing and reveals the critical influence of body motion on visuomotor processing. Motion illusions can reveal important shared principles of information processing across taxa.
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Ding Y, Naber M, Paffen CLE, Fabius JH, Van der Stigchel S. Saccades reset the priority of visual information to access awareness. Vision Res 2020; 173:1-6. [PMID: 32438013 DOI: 10.1016/j.visres.2020.04.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 04/09/2020] [Accepted: 04/23/2020] [Indexed: 11/18/2022]
Abstract
Subjectively, we experience a stable representation of the outside world across saccades. Although previous studies have reported that presaccadically acquired visual information influences postsaccadic perception, whether such information's priority to access visual awareness is either reset by each saccade or continuous across saccades remains unclear. To investigate this issue, we combined a breaking continuous flash suppression (b-CFS) with a saccade task. Before each saccade, a grating was presented in the peripheral visual field under suppression. After the saccade, the same grating was again presented under suppression at either the retinotopically matched, the spatiotopically matched, or a control location. By measuring the duration of the grating to break through CFS into awareness after a saccade, we could compare the breakthrough times across stimuli presented at the different locations. No difference in the reaction times between the spatiotopic and control location was observed, indicating that a saccade resets the buildup of an object's priority to access visual awareness. However, a longer breakthrough time was observed for the retinotopic as compared to the control location, suggesting that a form of retinotopic adaptation to the grating suppressed the priority to access visual awareness after a saccade.
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Fabius JH, Nijboer TCW, Fracasso A, Van der Stigchel S. Intra-saccadic displacement sensitivity after a lesion to the posterior parietal cortex. Cortex 2020; 127:108-119. [PMID: 32172025 PMCID: PMC7254053 DOI: 10.1016/j.cortex.2020.01.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 12/20/2019] [Accepted: 01/28/2020] [Indexed: 11/25/2022]
Abstract
Visual perception is introspectively stable and continuous across eye movements. It has been hypothesized that displacements in retinal input caused by eye movements can be dissociated from displacements in the external world using extra-retinal information, such as a corollary discharge from the oculomotor system. The extra-retinal information can inform the visual system about an upcoming eye movement and accompanying displacements in retinal input. The parietal cortex has been hypothesized to be critically involved in integrating retinal and extra-retinal information. Two tasks have been widely used to assess the quality of this integration: double-step saccades and intra-saccadic displacements. Double-step saccades performed by patients with parietal cortex lesions seemed to show hypometric second saccades. However, recently idea has been refuted by demonstrating that patients with very similar lesions were able to perform the double step saccades, albeit taking multiple saccades to reach the saccade target. So, it seems that extra-retinal information is still available for saccade execution after a lesion to the parietal lobe. Here, we investigated whether extra-retinal signals are also available for perceptual judgements in nine patients with strokes affecting the posterior parietal cortex. We assessed perceptual continuity with the intra-saccadic displacement task. We exploited the increased sensitivity when a small temporal blank is introduced after saccade offset (blank effect). The blank effect is thought to reflect the availability of extra-retinal signals for perceptual judgements. Although patients exhibited a relative difference to control subjects, they still demonstrated the blank effect. The data suggest that a lesion to the posterior parietal cortex (PPC) alters the processing of extra-retinal signals but does not abolish their influence altogether.
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Mitoma H, Buffo A, Gelfo F, Guell X, Fucà E, Kakei S, Lee J, Manto M, Petrosini L, Shaikh AG, Schmahmann JD. Consensus Paper. Cerebellar Reserve: From Cerebellar Physiology to Cerebellar Disorders. CEREBELLUM (LONDON, ENGLAND) 2020; 19:131-153. [PMID: 31879843 PMCID: PMC6978437 DOI: 10.1007/s12311-019-01091-9] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cerebellar reserve refers to the capacity of the cerebellum to compensate for tissue damage or loss of function resulting from many different etiologies. When the inciting event produces acute focal damage (e.g., stroke, trauma), impaired cerebellar function may be compensated for by other cerebellar areas or by extracerebellar structures (i.e., structural cerebellar reserve). In contrast, when pathological changes compromise cerebellar neuronal integrity gradually leading to cell death (e.g., metabolic and immune-mediated cerebellar ataxias, neurodegenerative ataxias), it is possible that the affected area itself can compensate for the slowly evolving cerebellar lesion (i.e., functional cerebellar reserve). Here, we examine cerebellar reserve from the perspective of the three cornerstones of clinical ataxiology: control of ocular movements, coordination of voluntary axial and appendicular movements, and cognitive functions. Current evidence indicates that cerebellar reserve is potentiated by environmental enrichment through the mechanisms of autophagy and synaptogenesis, suggesting that cerebellar reserve is not rigid or fixed, but exhibits plasticity potentiated by experience. These conclusions have therapeutic implications. During the period when cerebellar reserve is preserved, treatments should be directed at stopping disease progression and/or limiting the pathological process. Simultaneously, cerebellar reserve may be potentiated using multiple approaches. Potentiation of cerebellar reserve may lead to compensation and restoration of function in the setting of cerebellar diseases, and also in disorders primarily of the cerebral hemispheres by enhancing cerebellar mechanisms of action. It therefore appears that cerebellar reserve, and the underlying plasticity of cerebellar microcircuitry that enables it, may be of critical neurobiological importance to a wide range of neurological/neuropsychiatric conditions.
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Knox PC, Pasunuru N. Age-related alterations in inhibitory control investigated using the minimally delayed oculomotor response task. PeerJ 2020; 8:e8401. [PMID: 31942260 PMCID: PMC6955103 DOI: 10.7717/peerj.8401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 12/16/2019] [Indexed: 02/02/2023] Open
Abstract
Healthy, older adults are widely reported to experience cognitive decline, including impairments in inhibitory control. However, this general proposition has recently come under scrutiny because ageing effects are highly variable between individuals, are task dependent, and are sometimes not distinguished from general age-related slowing. We recently developed the minimally delayed oculomotor response (MDOR) task in which participants are presented with a simple visual target step, and instructed to saccade not to the target when it appears (a prosaccade response), but when it disappears (i.e. on target offset). Varying the target display duration (TDD) prevents offset timing being predictable from the time of target onset, and saccades prior to the offset are counted as errors. A comparison of MDOR task performance in a group of 22 older adults (mean age 62 years, range 50-72 years) with that in a group of 39 younger adults (22 years, range 19-27 years) demonstrated that MDOR latency was significantly increased in the older group by 34-68 ms depending on TDD. However, when MDOR latencies were corrected by subtracting the latency observed in a standard prosaccade task, the latency difference between groups was abolished. There was a larger latency modulation with TDD in the older group which was observed even when their generally longer latencies were taken into account. Error rates were significantly increased in the older group. An analysis of the timing distribution of errors demonstrated that most errors were failures to inhibit responses to target onsets. When error distributions were used to isolate clear inhibition failures from other types of error, the older group still exhibited significantly higher error rates as well as a higher residual error rate. Although MDOR latency in older participants may largely reflect a general slowing in the oculomotor system with age, both the latency modulation and error rate results are consistent with an age-related inhibitory control deficit. How this relates to performance on other inhibitory control tasks remains to be investigated.
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Abstract
In animals with good eyesight most eye movements consist of saccades, which rapidly shift the direction of the eye's axis, and intervals between the saccades (fixations) in which gaze is kept stationary relative to the surroundings. This stability is needed to prevent motion blur, and it is achieved by reflexes which counter-rotate the eye when the head moves. This saccade-and-fixate strategy arose early in fish evolution, when the original function of saccades was to re-centre the eye as the fish turned. In primates, and other foveate vertebrates, saccades took on the new function of directing the fovea to objects of interest in the surroundings. Among invertebrates the same saccade-and-fixate pattern is seen, especially in insects, crustaceans and cephalopod molluscs.
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Nagai K, Kaneko Y, Suzuki M, Teramoto H, Morita A, Kamei S, Watanabe Y, Okada M, Uchiyama M. Multimodal visual exploration disturbances in Parkinson's disease detected with an infrared eye-movement assessment system. Neurosci Res 2019; 160:50-56. [PMID: 31715198 DOI: 10.1016/j.neures.2019.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 10/03/2019] [Accepted: 11/07/2019] [Indexed: 12/25/2022]
Abstract
Parkinson's disease (PD) reportedly show disturbed visual exploration. However, whether this disturbance is due to dysfunctional visual information processing remains unclear. To clarify the effects of PD on visual information processing when exploring for targets and to compare disease effects with aging effects, we used an infrared eye-movement assessment system. Cognitively normal PD patients (n = 13), healthy age-matched (n = 17) and young controls (n = 36) participated in this study, and were evaluated using two figure-matching tasks representing visual information processing (clock-matching and inverted clock-matching tasks) and saccade tasks representing oculomotor function. With figure-matching tasks, PD patients showed significantly larger numbers of images watched in a single trial compared to healthy age-matched controls on the inverted clock-matching task. No aging effects was found in these variables. In contrast, no disease effect was apparent for reaction time, which was significantly longer in healthy age-matched controls than in healthy young controls. For saccade tasks, PD patients showed significantly smaller saccade size than healthy age-matched controls on the antisaccade task, but no aging effects were evident. Our approaches highlighted that visual exploration disturbance in PD may be due to dysfunctional visual information processing in addition to dysfunctional oculomotor processing. These disease effects may differ from aging effects.
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Yamazaki A, Ikeda T, Tsutsumi T. Main sequence of torsional saccadic eye movement - analysis by three-dimensional video-oculography. Acta Otolaryngol 2019; 139:987-989. [PMID: 31512541 DOI: 10.1080/00016489.2019.1659998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Background: Quantification of main sequence is required for three-dimensional recording and analysis of eye movement using video-oculography. However, the main sequence of torsional saccade has not been reported to the best of our knowledge. Aims/objectives: To obtain characteristics of torsional saccade using infra-red video-oculography, and to analyse the main sequence. Material and methods: Torsional saccades of 10 healthy subjects were extracted from torsional vestibulo-ocular reflex from voluntary head rotation. Angular velocities were plotted against amplitude of each saccade to obtain the main sequence of torsional saccade. Results: Main sequence of torsional saccade demonstrated non-linear characteristic. The adduction amplitude was significantly larger than abduction, while there was no significant difference in time constants. Conclusions and significance: Torsional saccade demonstrates non-linear characteristic, similar to main sequence of vertical and horizontal saccades.
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McSorley E, Gilchrist ID, McCloy R. The role of fixation disengagement in the parallel programming of sequences of saccades. Exp Brain Res 2019; 237:3033-3045. [PMID: 31531688 PMCID: PMC6794246 DOI: 10.1007/s00221-019-05641-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 08/28/2019] [Indexed: 12/02/2022]
Abstract
One of the core mechanisms involved in the control of saccade responses to selected target stimuli is the disengagement from the current fixation location, so that the next saccade can be executed. To carry out everyday visual tasks, we make multiple eye movements that can be programmed in parallel. However, the role of disengagement in the parallel programming of saccades has not been examined. It is well established that the need for disengagement slows down saccadic response time. This may be important in allowing the system to program accurate eye movements and have a role to play in the control of multiple eye movements but as yet this remains untested. Here, we report two experiments that seek to examine whether fixation disengagement reduces saccade latencies when the task completion demands multiple saccade responses. A saccade contingent paradigm was employed and participants were asked to execute saccadic eye movements to a series of seven targets while manipulating when these targets were shown. This both promotes fixation disengagement and controls the extent that parallel programming can occur. We found that trial duration decreased as more targets were made available prior to fixation: this was a result both of a reduction in the number of saccades being executed and in their saccade latencies. This supports the view that even when fixation disengagement is not required, parallel programming of multiple sequential saccadic eye movements is still present. By comparison with previous published data, we demonstrate a substantial speeded of response times in these condition ("a gap effect") and that parallel programming is attenuated in these conditions.
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Thakkar KN, Rolfs M. Disrupted Corollary Discharge in Schizophrenia: Evidence From the Oculomotor System. BIOLOGICAL PSYCHIATRY. COGNITIVE NEUROSCIENCE AND NEUROIMAGING 2019; 4:773-781. [PMID: 31105039 PMCID: PMC6733648 DOI: 10.1016/j.bpsc.2019.03.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 03/04/2019] [Accepted: 03/22/2019] [Indexed: 01/18/2023]
Abstract
Corollary discharge (CD) signals are motor-related signals that exert an influence on sensory processing. They allow mobile organisms to predict the sensory consequences of their imminent actions. Among the many functions of CD is to provide a means by which we can distinguish sensory experiences caused by our own actions from those with external causes. In this way, they contribute to a subjective sense of agency. A disruption in the sense of agency is central to many of the clinical symptoms of schizophrenia, and abnormalities in CD signaling have been theorized to underpin particularly those agency-related psychotic symptoms of the illness. Characterizing abnormal CD associated with eye movements in schizophrenia and their resulting influence on visual processing and subsequent action plans may have advantages over other sensory and motor systems. That is because the most robust psychophysiological and neurophysiological data regarding the dynamics and influence of CD as well as the neural circuitry implicated in CD generation and transmission comes from the study of eye movements in humans and nonhuman primates. We review studies of oculomotor CD signaling in the schizophrenia spectrum and possible neurobiological correlates of CD disturbances. We conclude by speculating on the ways in which oculomotor CD dysfunction, specifically, may invoke specific experiences, clinical symptoms, and cognitive impairments. These speculations lay the groundwork for empirical study, and we conclude by outlining potentially fruitful research directions.
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The temporal and spatial constraints of saccade planning to double-step target displacements. Vision Res 2019; 163:1-13. [PMID: 31404552 DOI: 10.1016/j.visres.2019.08.003] [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: 11/26/2018] [Revised: 06/30/2019] [Accepted: 08/06/2019] [Indexed: 11/20/2022]
Abstract
The double-step paradigm investigates the characteristics of planning and execution when the motor system must rapidly adjust for a new goal location. Studies have provided detailed temporal information based on the duration available for the motor system to prepare a new movement trajectory (here referred to as re-preparation time). However, previous work has largely examined single displacement sizes, limiting the spatiotemporal understanding of movement planning and execution. The lack of a description of this behavioral timecourse across increasing displacement sizes is true for saccades, rapid eye movements that redirect the fovea. Furthermore, during the double-step paradigm, the primary saccade often fails to accurately foveate the final target location and a secondary saccade brings the target onto the fovea. However, it is also unknown how this compensation is concurrently modified with the exposure duration and displacement of the movement goal. Here, we examined the amount of time required to change the initial saccade direction to a new target location for relatively small (20°, 30°, and 40°) and large (60° and 90°) target spatial separations. Interestingly, we found a clear relationship between the saccade direction and the amount of time allowed to redirect the movement; across separations, intermediate saccades occurred when approximately 60-140 ms was available to readjust the movement plan. Additionally, there was a consistent relationship between the timing of the secondary saccade and the re-preparation time across jump sizes, suggesting that concurrent movement correction planning was dependent on the amount of exposure to the final movement goal.
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Eggert T, Straube A. Saccade variability in healthy subjects and cerebellar patients. PROGRESS IN BRAIN RESEARCH 2019; 249:141-152. [PMID: 31325974 DOI: 10.1016/bs.pbr.2019.03.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/01/2023]
Abstract
In a previous study we developed a model for the inter-trial variance of saccade trajectories in the rhesus macaque. The analysis of that model showed that signal-dependent noise results in different effector variabilities depending on whether the noise is propagated feedforward through the system (accumulating noise) or whether the noise originates from inside of a premotor feedback loop (feedback noise). This allowed the gain of the premotor feedback loop to be estimated directly from behavioral data. In the present study, we applied the model in healthy human subjects and in patients with chronic isolated cerebellar lesions due to ischemic stroke. Humans showed smaller noise coefficients of variation for both accumulating noise and feedback noise and smaller feedback gain than the monkeys. Despite these differences in the model parameters, the qualitative differences between the two noise types were similar in both species. Cerebellar patients showed larger inter-trial variance of saccade amplitude compared to controls, but saccade metrics and dynamics were well compensated. The parameters of the noise model did not differ significantly between groups. The variance of the saccade amplitude correlated highly (r=0.95) with the coefficient of variation of accumulating noise but not with the other model parameters. The results suggest that the cerebellum plays a role not only in premotor feedback but also in feedforward saccade control and that the latter is responsible for increased endpoint variance in cerebellar patients.
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Shaikh AG, Zee DS. Eye Movement Research in the Twenty-First Century-a Window to the Brain, Mind, and More. THE CEREBELLUM 2019; 17:252-258. [PMID: 29260439 DOI: 10.1007/s12311-017-0910-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The study of eye movements not only addresses debilitating neuro-ophthalmological problems but has become an essential tool of basic neuroscience research. Eye movements are a classic way to evaluate brain function-traditionally in disorders affecting the brainstem and cerebellum. Abnormalities of eye movements have localizing value and help narrow the differential diagnosis of complex neurological problems. More recently, using sophisticated behavioral paradigms, measurement of eye movements has also been applied to disorders of the thalamus, basal ganglia, and cerebral cortex. Moreover, in contemporary neuroscience, eye movements play a key role in understanding cognition, behavior, and disorders of the mind. Examples include applications to higher-level decision-making processes as in neuroeconomics and psychiatric and cognitive disorders such as schizophrenia and autism. Eye movements have become valued as objective biomarkers to monitor the natural progression of disease and the effects of therapies. As specific genetic defects are identified for many neurological disorders, ocular motor function often becomes the cornerstone of phenotypic classification and differential diagnosis. Here, we introduce other important applications of eye movement research, including understanding movement disorders affecting the head and limbs. We also emphasize the need to develop standardized test batteries for eye movements of all types including the vestibulo-ocular responses. The evaluation and treatment of patients with cerebellar ataxia are particularly amenable to such an approach.
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Mayadali ÜS, Lienbacher K, Mustari M, Strupp M, Horn AKE. Potassium channels in omnipause neurons. PROGRESS IN BRAIN RESEARCH 2019; 249:117-123. [PMID: 31325972 DOI: 10.1016/bs.pbr.2019.04.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
Potassium (K+) channels are major contributors to fast and precise action potential generation. The aim of this study was to establish the immunoreactivity profile of several potassium channels in omnipause neurons (OPNs), which play a central role in premotor saccadic circuitry. To accomplish this, we histochemically examined monkey and human brainstem sections using antibodies against the voltage gated K+-channels KV1.1, KV3.1b and K+-Cl- cotransporter (KCC2). We found that OPNs of both species were positive for all three K+-antibodies and that the staining patterns were similar for both species. In individual OPNs, KV3.1b was detected on the somatic membrane and proximal dendrites, while KV1.1 was mainly confined to soma. Further, KCC2 immunoreactivity was strong in distal dendrites, but was weak in the somatic membrane. Our findings allow the speculation that the alterations in K+-channel expression in OPNs could be the underlying mechanism for several saccadic disorders through neuronal and circuit-level malfunction.
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Ray A, Subramanian A, Chhabra H, Kommu JVS, Venkatsubramanian G, Srinath S, Girimaji S, Sheshadri SP, Philip M. Eye movement tracking in pediatric obsessive compulsive disorder. Asian J Psychiatr 2019; 43:9-16. [PMID: 31075652 DOI: 10.1016/j.ajp.2019.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Revised: 04/04/2019] [Accepted: 04/22/2019] [Indexed: 10/26/2022]
Abstract
Till date researchers have elucidated the neurobiological substrates in OCD using methods like neuroimaging. However, a potential biomarker is still elusive. The present study is an attempt to identify a potential biomarker in pediatric OCD using eye tracking. The present study measured pro-saccade and anti-saccade parameters in 36 cases of pediatric OCD and 31 healthy controls. There was no significant difference between cases and controls in the error rate, peak velocity, position gain and latency measures in both pro-saccade and anti-saccade eye tracking tasks. With age, anti-saccades become slower in velocity, faster in response and more accurate irrespective of disorder status of the child. Pro-saccades also show a similar effect that is less prominent than anti-saccades. Gain measures more significantly vary with age in children with OCD than the controls, whereas latency measures positively correlated with age in children with OCD as opposed to being negatively correlated in the controls. Findings of this study do not support any of the eye tracking measures as putative diagnostic bio-markers in OCD. However, latency and gain parameters across different age groups in anti-saccade tasks need to be explored in future studies.
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Tang SY, Shaikh AG. Past and Present of Eye Movement Abnormalities in Ataxia-Telangiectasia. CEREBELLUM (LONDON, ENGLAND) 2019; 18:556-564. [PMID: 30523550 PMCID: PMC6751135 DOI: 10.1007/s12311-018-0990-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Ataxia-telangiectasia is the second most common autosomal recessive hereditary ataxia, with an estimated incidence of 1 in 100,000 births. Besides ataxia and ocular telangiectasias, eye movement abnormalities have long been associated with this disorder and is frequently present in almost all patients. A handful of studies have described the phenomenology of ocular motor deficits in ataxia-telangiectasia. Contemporary literature linked their physiology to cerebellar dysfunction and secondary abnormalities at the level of brainstem. These studies, while providing a proof of concept of ocular motor physiology in disease, i.e., ataxia-telangiectasia, also advanced our understanding of how the cerebellum works. Here, we will summarize the clinical abnormalities seen with ataxia-telangiectasia in each subtype of eye movements and subsequently describe the underlying pathophysiology. Finally, we will review how these deficits are linked to abnormal cerebellar function and how it allows better understanding of the cerebellar physiology.
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Takahashi M. Morphological and electrophysiological characteristics of the commissural system in the superior colliculi for control of eye movements. PROGRESS IN BRAIN RESEARCH 2019; 249:105-115. [PMID: 31325971 DOI: 10.1016/bs.pbr.2019.04.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Commissural connections between the superior colliculi (SCs) were well known anatomically, and assumed to be only inhibitory in relation to visual inputs. However, by recording intracellular potentials, we revealed that a strong monosynaptic excitatory commissural connection exists between the rostral SCs of the cat. Commissural excitation existed between the medial-medial or lateral-lateral parts of both SCs, while commissural inhibition existed between the medial SC on one side and the lateral SC on the opposite side. These commissural excitation and inhibition were also confirmed morphologically with the double-labeling method of HRP-conjugated gold particle and GABA. Similarity of the topography of commissural inhibition between the SC system and the vestibuloocular system supported the conclusion that the saccadic eye movement system uses the same semicircular canal coordinate as the vestibuloocular system. The commissural excitation may help to maintain Listing's law in saccadic eye movements.
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Goffart L. Kinematics and the neurophysiological study of visually-guided eye movements. PROGRESS IN BRAIN RESEARCH 2019; 249:375-384. [PMID: 31325996 DOI: 10.1016/bs.pbr.2019.03.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
How do we relate observations and measurements made at the behavioral and neuronal levels? Notions of kinematics have been used to "decode" the firing rate of neurons and to explain the neurophysiology underlying the generation of visually-guided eye movements. The appropriateness of their fitting to events occurring within a medium (the brain) radically different from the physical world is questioned in this chapter. Instead of embedding the eye kinematics in the firing rate of central neurons, we propose that the saccadic and pursuit eye movements in fact reflect the dynamics of transitions of brain activity, from unbalanced states to equilibrium (symmetry) between opposing directional tendencies carried by the recruited visuomotor channels, with distinct transitions characterizing each movement category. While the eyeballs conform to the physical laws of motion, the neural processes leading to their movements follow principles dictated by the intrinsic properties of the brain network and of its diverse neurons.
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A neuronal process for adaptive control of primate saccadic system. PROGRESS IN BRAIN RESEARCH 2019; 249:169-181. [PMID: 31325976 DOI: 10.1016/bs.pbr.2019.03.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
In 1980, Dr. Optican established the existence of an adaptive plasticity of saccades and its dependence on the cerebellum with Dr. Robinson. The advantage of saccades is that the neuronal mechanisms underlying their generation have been well established. This knowledge allows us to identify the neuronal elements that participate in saccade adaptation. Briefly, the superior colliculus (SC) produces a saccade command signal, which reaches motoneurons in the abducens nucleus via the brainstem burst generator. The SC saccade command also is sent to the oculomotor vermis (OMV), a saccade-related area of the cerebellar cortex, and finally converges on the same motoneurons via the caudal fastigial nucleus (cFN) and inhibitory burst neurons (IBN). During adaptation, the saccade-related burst of SC neurons does not change; however, the activity of the cerebellum and its downstream targets do. We demonstrate that the SC is the source of the error signal to the OMV, and the error signal increases the probability of complex spike occurrence and decreases simple spike activity in the OMV. This decrease, in turn, is delivered through the cFN and IBN neurons to decrease motoneuron activity and hence saccade amplitude.
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Obyedkov I, Skuhareuskaya M, Skugarevsky O, Obyedkov V, Buslauski P, Skuhareuskaya T, Waszkiewicz N. Saccadic eye movements in different dimensions of schizophrenia and in clinical high-risk state for psychosis. BMC Psychiatry 2019; 19:110. [PMID: 30961571 PMCID: PMC6454611 DOI: 10.1186/s12888-019-2093-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 03/27/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Oculomotor dysfunction is one of the most replicated findings in schizophrenia. However the association between saccadic abnormalities and particular clinical syndromes remains unclear. The assessment of saccadic movements in schizophrenia patients as well as in clinical high-risk state for psychosis individuals (CHR) as a part of schizophrenia continuum may be useful in validation of saccadic movements as a possible biomarker. METHODS The study included 156 patients who met the ICD-10 criteria for schizophrenia: 42 individuals at clinical high-risk-state for psychosis and 61 healthy controls. The schizophrenia patients had three subgroups based on the sum of the global SAPS and SANS scores: (1) patients with predominantly negative symptoms (NS, n = 62); (2) patients with predominantly positive symptoms (PS, n = 54) (3) patients with predominantly disorganization symptoms (DS, n = 40). CHR subjects were characterized by the presence of one of the groups of criteria: (1) Ultra High Risk criteria, (2) Basic Symptoms criteria or (3) negative symptoms and formal thought disorders. Horizontal eye movements were recorded by using videonystagmograph. We measured peak velocity, latency and accuracy in prosaccade, antisaccade and predictive saccade tasks as well as error rates in the antisaccade task. RESULTS Schizophrenia patients performed worse than controls in predictive, reflexive and antisaccade tasks. Oculomotor parameters of NS were different from the other groups of patients. Latencies of predictive and reflexive saccades were significantly longer than in controls only in the NS group. The accuracy of predictive saccades was also different from controls only in the NS schizophrenia group. More prominent loss of accuracy of reflexive saccades was found in the DS group and it significantly differed from the one in other groups. Participants from DS group made more errors in antisaccade task compared to NS and PS groups. CHR subjects performed worse than controls as measured by the accuracy of reflexive saccades and antisaccades. CONCLUSIONS The study confirms the existence of different relations between the symptom dimensions of schizophrenia and saccades tasks performances. Saccadic abnormalities were revealed in the clinical (schizophrenia) and pre-clinical (clinical high risk) populations that provide further evidence for assessing saccadic abnormalities as a possible neurobiological marker for schizophrenia.
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