The Experts below are selected from a list of 23763 Experts worldwide ranked by ideXlab platform
Alessandra Rufa - One of the best experts on this subject based on the ideXlab platform.
-
differences in Saccade dynamics between spinocerebellar ataxia 2 and late onset cerebellar ataxias
Brain, 2011Co-Authors: Pamela Federighi, Gabriele Cevenini, Maria Teresa Dotti, Francesca Rosini, Elena Pretegiani, Antonio Federico, Alessandra RufaAbstract:The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by Saccade kinetic abnormalities. The study of Saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of Saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary Saccades of different amplitude (10°–18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of Saccade parameters and measures of Saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak Saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar Saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with Saccade amplitude. The percentage of hypometric primary Saccades and of larger secondary corrective Saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow Saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to Saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric Saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow Saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target. * Abbreviations : ICARS : international cooperative ataxia rating scale SCA2 : spinocerebellar ataxia type 2
-
differences in Saccade dynamics between spinocerebellar ataxia 2 and late onset cerebellar ataxias
Brain, 2011Co-Authors: Pamela Federighi, Gabriele Cevenini, Maria Teresa Dotti, Francesca Rosini, Elena Pretegiani, Antonio Federico, Alessandra RufaAbstract:The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by Saccade kinetic abnormalities. The study of Saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of Saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary Saccades of different amplitude (10°-18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of Saccade parameters and measures of Saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak Saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar Saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with Saccade amplitude. The percentage of hypometric primary Saccades and of larger secondary corrective Saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow Saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to Saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric Saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow Saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target.
Pamela Federighi - One of the best experts on this subject based on the ideXlab platform.
-
differences in Saccade dynamics between spinocerebellar ataxia 2 and late onset cerebellar ataxias
Brain, 2011Co-Authors: Pamela Federighi, Gabriele Cevenini, Maria Teresa Dotti, Francesca Rosini, Elena Pretegiani, Antonio Federico, Alessandra RufaAbstract:The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by Saccade kinetic abnormalities. The study of Saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of Saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary Saccades of different amplitude (10°–18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of Saccade parameters and measures of Saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak Saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar Saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with Saccade amplitude. The percentage of hypometric primary Saccades and of larger secondary corrective Saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow Saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to Saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric Saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow Saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target. * Abbreviations : ICARS : international cooperative ataxia rating scale SCA2 : spinocerebellar ataxia type 2
-
differences in Saccade dynamics between spinocerebellar ataxia 2 and late onset cerebellar ataxias
Brain, 2011Co-Authors: Pamela Federighi, Gabriele Cevenini, Maria Teresa Dotti, Francesca Rosini, Elena Pretegiani, Antonio Federico, Alessandra RufaAbstract:The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by Saccade kinetic abnormalities. The study of Saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of Saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary Saccades of different amplitude (10°-18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of Saccade parameters and measures of Saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak Saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar Saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with Saccade amplitude. The percentage of hypometric primary Saccades and of larger secondary corrective Saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow Saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to Saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric Saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow Saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target.
Denis Pelisson - One of the best experts on this subject based on the ideXlab platform.
-
Are Covert Saccade Functionally Relevant in Vestibular Hypofunction?
The Cerebellum, 2018Co-Authors: R. Hermann, Denis Pelisson, O Dumas, Ch Urquizar, E. Truy, Caroline TiliketeAbstract:The vestibulo-ocular reflex maintains gaze stabilization during angular or linear head accelerations, allowing adequate dynamic visual acuity. In case of bilateral vestibular hypofunction, patients use Saccades to compensate for the reduced vestibulo-ocular reflex function, with covert Saccades occurring even during the head displacement. In this study, we questioned whether covert Saccades help maintain dynamic visual acuity, and evaluated which characteristic of these Saccades are the most relevant to improve visual function. We prospectively included 18 patients with chronic bilateral vestibular hypofunction. Subjects underwent evaluation of dynamic visual acuity in the horizontal plane as well as video recording of their head and eye positions during horizontal head impulse tests in both directions (36 ears tested). Frequency, latency, consistency of covert Saccade initiation, and gain of covert Saccades as well as residual vestibulo-ocular reflex gain were calculated. We found no correlation between residual vestibulo-ocular reflex gain and dynamic visual acuity. Dynamic visual acuity performance was however positively correlated with the frequency and gain of covert Saccades and negatively correlated with covert Saccade latency. There was no correlation between consistency of covert Saccade initiation and dynamic visual acuity. Even though gaze stabilization in space during covert Saccades might be of very short duration, these refixation Saccades seem to improve vision in patients with bilateral vestibular hypofunction during angular head impulses. These findings emphasize the need for specific rehabilitation technics that favor the triggering of covert Saccades. The physiological origin of covert Saccades is discussed.
-
Brain Processing of Visual Information during Fast Eye Movements Maintains Motor Performance
PLoS ONE, 2013Co-Authors: Muriel Panouilleres, Christian Urquizar, Valérie Gaveau, Camille Socasau, Denis PelissonAbstract:Movement accuracy depends crucially on the ability to detect errors while actions are being performed. When inaccuracies occur repeatedly, both an immediate motor correction and a progressive adaptation of the motor command can unfold. Of all the movements in the motor repertoire of humans, saccadic eye movements are the fastest. Due to the high speed of Saccades, and to the impairment of visual perception during Saccades, a phenomenon called ''saccadic suppression'', it is widely believed that the adaptive mechanisms maintaining saccadic performance depend critically on visual error signals acquired after Saccade completion. Here, we demonstrate that, contrary to this widespread view, saccadic adaptation can be based entirely on visual information presented during Saccades. Our results show that visual error signals introduced during Saccade execution-by shifting a visual target at Saccade onset and blanking it at Saccade offset-induce the same level of adaptation as error signals, presented for the same duration, but after Saccade completion. In addition, they reveal that this processing of intra-saccadic visual information for adaptation depends critically on visual information presented during the deceleration phase, but not the acceleration phase, of the Saccade. These findings demonstrate that the human central nervous system can use short intra-saccadic glimpses of visual information for motor adaptation, and they call for a reappraisal of current models of saccadic adaptation.
-
Effect of saccadic adaptation on sequences of Saccades
Journal of Eye Movement Research, 2012Co-Authors: Muriel Panouilleres, Christian Urquizar, Romeo Salemme, Denis PelissonAbstract:Accuracy of saccadic eye movements is maintained thanks to adaptation mechanisms. The adaptive lengthening and shortening of reactive and voluntary Saccades rely on partially separate neural substrates. Although in daily-life we mostly perform sequences of Saccades, the effect of saccadic adaptation has been mainly evaluated on single Saccades. Here, sequences of two Saccades were recorded before and after adaptation of rightward Saccades. In 4 separate sessions, reactive and voluntary Saccades were adaptively shortened or lengthened. We found that the second Saccade of the sequence always remained accurate and compensated for the adaptive changes of the first rightward Saccade size. This finding suggests that adaptation loci are upstream of the site where the efference copy involved in sequence planning originates.
-
sensory processing of motor inaccuracy depends on previously performed movement and on subsequent motor corrections a study of the saccadic system
PLOS ONE, 2011Co-Authors: Muriel Panouilleres, Christian Urquizar, Romeo Salemme, Denis PelissonAbstract:When goal-directed movements are inaccurate, two responses are generated by the brain: a fast motor correction toward the target and an adaptive motor recalibration developing progressively across subsequent trials. For the saccadic system, there is a clear dissociation between the fast motor correction (corrective Saccade production) and the adaptive motor recalibration (primary Saccade modification). Error signals used to trigger corrective Saccades and to induce adaptation are based on post-saccadic visual feedback. The goal of this study was to determine if similar or different error signals are involved in saccadic adaptation and in corrective Saccade generation. Saccadic accuracy was experimentally altered by systematically displacing the visual target during motor execution. Post-saccadic error signals were studied by manipulating visual information in two ways. First, the duration of the displaced target after primary Saccade termination was set at 15, 50, 100 or 800 ms in different adaptation sessions. Second, in some sessions, the displaced target was followed by a visual mask that interfered with visual processing. Because they rely on different mechanisms, the adaptation of reactive Saccades and the adaptation of voluntary Saccades were both evaluated. We found that saccadic adaptation and corrective Saccade production were both affected by the manipulations of post-saccadic visual information, but in different ways. This first finding suggests that different types of error signal processing are involved in the induction of these two motor corrections. Interestingly, voluntary Saccades required a longer duration of post-saccadic target presentation to reach the same amount of adaptation as reactive Saccades. Finally, the visual mask interfered with the production of corrective Saccades only during the voluntary Saccades adaptation task. These last observations suggest that post-saccadic perception depends on the previously performed action and that the differences between Saccade categories of motor correction and adaptation occur at an early level of visual processing.
-
Adaptation of voluntary Saccades, but not of reactive Saccades, transfers to hand pointing movements
Journal of Neurophysiology, 2007Co-Authors: Julien Cotti, Denis Pelisson, Alain Guillaume, Nadia Alahyane, Jean-louis VercherAbstract:Studying the transfer of visuomotor adaptation from a given effector (e. g., the eye) to another (e. g., the hand) allows us to question whether sensorimotor processes influenced by adaptation are common to both effector control systems and thus to address the level where adaptation takes place. Previous studies have shown only very weak transfer of the amplitude adaptation of reactive Saccades - i. e., produced automatically in response to the sudden appearance of visual targets - to hand pointing movements. Here we compared the amplitude of hand pointing movements recorded before and after adaptation of either reactive or voluntary Saccades, produced either in a Saccade sequence task or in a single Saccade task. No transfer to hand pointing movements was found after adaptation of reactive Saccades. In contrast, a substantial transfer to the hand was obtained following adaptation of voluntary Saccades produced in sequence. Large amounts of transfer between the two Saccade types were also found. These results demonstrate that the visuomotor processes influenced by saccadic adaptation depend on the type of Saccades and that, in the case of voluntary Saccades, they are shared by hand pointing movements. Implications for the neurophysiological substrates of the adaptation of reactive and voluntary Saccades are discussed.
Maria Teresa Dotti - One of the best experts on this subject based on the ideXlab platform.
-
differences in Saccade dynamics between spinocerebellar ataxia 2 and late onset cerebellar ataxias
Brain, 2011Co-Authors: Pamela Federighi, Gabriele Cevenini, Maria Teresa Dotti, Francesca Rosini, Elena Pretegiani, Antonio Federico, Alessandra RufaAbstract:The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by Saccade kinetic abnormalities. The study of Saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of Saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary Saccades of different amplitude (10°–18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of Saccade parameters and measures of Saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak Saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar Saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with Saccade amplitude. The percentage of hypometric primary Saccades and of larger secondary corrective Saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow Saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to Saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric Saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow Saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target. * Abbreviations : ICARS : international cooperative ataxia rating scale SCA2 : spinocerebellar ataxia type 2
-
differences in Saccade dynamics between spinocerebellar ataxia 2 and late onset cerebellar ataxias
Brain, 2011Co-Authors: Pamela Federighi, Gabriele Cevenini, Maria Teresa Dotti, Francesca Rosini, Elena Pretegiani, Antonio Federico, Alessandra RufaAbstract:The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by Saccade kinetic abnormalities. The study of Saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of Saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary Saccades of different amplitude (10°-18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of Saccade parameters and measures of Saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak Saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar Saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with Saccade amplitude. The percentage of hypometric primary Saccades and of larger secondary corrective Saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow Saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to Saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric Saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow Saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target.
Elena Pretegiani - One of the best experts on this subject based on the ideXlab platform.
-
differences in Saccade dynamics between spinocerebellar ataxia 2 and late onset cerebellar ataxias
Brain, 2011Co-Authors: Pamela Federighi, Gabriele Cevenini, Maria Teresa Dotti, Francesca Rosini, Elena Pretegiani, Antonio Federico, Alessandra RufaAbstract:The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by Saccade kinetic abnormalities. The study of Saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of Saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary Saccades of different amplitude (10°–18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of Saccade parameters and measures of Saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak Saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar Saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with Saccade amplitude. The percentage of hypometric primary Saccades and of larger secondary corrective Saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow Saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to Saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric Saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow Saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target. * Abbreviations : ICARS : international cooperative ataxia rating scale SCA2 : spinocerebellar ataxia type 2
-
differences in Saccade dynamics between spinocerebellar ataxia 2 and late onset cerebellar ataxias
Brain, 2011Co-Authors: Pamela Federighi, Gabriele Cevenini, Maria Teresa Dotti, Francesca Rosini, Elena Pretegiani, Antonio Federico, Alessandra RufaAbstract:The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by Saccade kinetic abnormalities. The study of Saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of Saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary Saccades of different amplitude (10°-18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of Saccade parameters and measures of Saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak Saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar Saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with Saccade amplitude. The percentage of hypometric primary Saccades and of larger secondary corrective Saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow Saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to Saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric Saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow Saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target.
