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Smooth Pursuit (smooth + pursuit)

Distribution by Scientific Domains
Medical Sciences50%

Terms modified by Smooth Pursuit

  • smooth pursuit eye movement
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    Selected Abstracts

    Smooth ocular pursuit in Chiari type II malformation

    DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 4 2007
    Michael S Salman MRCP PhD
    Chiari type II malformation (CII) is a congenital anomaly of the cerebellum and brainstem, both important structures for processing smooth ocular pursuit. CII is associated with myelomeningocele and hydrocephalus. We investigated the effects of CII on smooth pursuit (SP) eye movements, and determined the effects of spinal lesion level, number of shunt revisions, nystagmus, and brain dysmorphology on SP. SP was recorded using an infrared eye tracker in 21 participants with CII (11 males, 10 females; age range 8-19y, mean 14y 3mo [SD 3y 2mo]). Thirty-eight healthy children (21 males, 17 females) constituted the comparison group. Participants followed a visual target moving sinusoidally at ± 10° amplitude, horizontally and vertically at 0.25 or 0.5Hz. SP gains, the ratio of eye to target velocities, were abnormal in the CII group with nystagmus (n= 8). The number of shunt revisions (range 0-10), brain dysmorphology, or spinal lesion level (n= 15 for lower and n= 6 for upper spinal lesion level) did not correlate with SP gains. SP is impaired in children with CII and nystagmus. Abnormal pursuit might be related to the CII dysgenesis or to effects of hydrocephalus. The lack of effect of shunt revisions and abnormal tracking in participants with nystagmus provide evidence that it is related primarily to the cerebellar and brainstem malformation. [source]

    Cortical mechanisms of smooth pursuit eye movements with target blanking.

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2004
    An fMRI study
    Abstract Smooth pursuit eye movements are evoked by retinal image motion of visible moving objects and can also be driven by the internal representation of a target due to extraretinal mechanisms (e.g. efference copy). To delineate the corresponding neuronal correlates, functional magnetic resonance imaging at 1.5 T was applied during smooth pursuit at 10 °/s with continuous target presentation and target blanking for 1 s to 16 right-handed healthy males. Eye movements were assessed during scanning sessions by infra-red reflection oculography. Smooth pursuit performance was optimal when the target was visible but decreased to a residual velocity of about 30% of the velocity observed during continuous target presentation. Random effects analysis of the imaging data yielded an activation pattern for smooth pursuit in the absence of a visual target (in contrast to continuous target presentation) which included a number of cortical areas in which extraretinal information is available such as the frontal eye field, the superior parietal lobe, the anterior and the posterior intraparietal sulcus and the premotor cortex, and also the supplementary and the presupplementary eye field, the supramarginal gyrus, the dorsolateral prefrontal cortex, cerebellar areas and the basal ganglia. We suggest that cortical mechanisms such as prediction, visuo-spatial attention and transformation, multimodal visuomotor control and working memory are of special importance for maintaining smooth pursuit eye movements in the absence of a visible target. [source]

    Single-neuron evidence for a contribution of the dorsal pontine nuclei to both types of target-directed eye movements, saccades and smooth-pursuit

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2004
    Peter W. Dicke
    Abstract The primate dorsolateral pontine nucleus (DLPN) is a key link in a cerebro-cerebellar pathway for smooth pursuit eye movements, a pathway assumed to be anatomically segregated from tegmental circuits subserving saccades. However, the existence of afferents from several cerebrocortical and subcortical centres for saccades suggests that the DLPN and neighbouring parts of the dorsal pontine nuclei (DPN) might contribute to saccades as well. In order to test this hypothesis, we recorded from the DPN of two monkeys trained to perform smooth pursuit eye movements as well as visually and memory-guided saccades. Out of 281 neurons isolated from the DPN, 138 were responsive in oculomotor tasks. Forty-five were exclusively activated in saccade paradigms, 68 exclusively by smooth pursuit and 25 neurons showed responses in both. Pursuit-related responses reflected sensitivity to eye position, velocity or combinations of velocity and position with minor contributions of acceleration in many cases. When tested in the memory-guided saccades paradigm, 65 out of 70 neurons activated in saccade paradigms showed significant saccade-related bursts and 20 significant activity in the memory period. Our finding of saccade-related activity in the DPN in conjunction with the existence of strong anatomical input from saccade-related cerebrocortical areas suggests that the DPN serves as a precerebellar relay for both pursuit and saccade-related information originating from cerebral cortex, in addition to the classical tecto-tegmental circuitry for saccades. [source]

    Decreased cortical inhibition and yet cerebellar pathology in ,familial cortical myoclonic tremor with epilepsy'

    MOVEMENT DISORDERS, Issue 16 2007
    Anne-Fleur van Rootselaar MD
    Abstract Cortical hyperexcitability is a feature of "familial cortical myoclonic tremor with epilepsy" (FCMTE). However, neuropathological investigations in a single FCMTE patient showed isolated cerebellar pathology. Pathological investigations in a second FCMTE patient, reported here, confirmed cerebellar Purkinje cell degeneration and a normal sensorimotor cortex. Subsequently, we sought to explore the nature of cerebellar and motor system pathophysiology in FCMTE. Eye movement recordings and transcranial magnetic stimulation performed in six related FCMTE patients showed impaired saccades and smooth pursuit and downbeat nystagmus upon hyperventilation, as in patients with spinocerebellar ataxia type 6. In FCMTE patients short-interval intracortical inhibition (SICI) was significantly reduced. Resting motor threshold, recruitment curve, silent period, and intracortical facilitation were normal. The neuropathological and ocular motor abnormalities indicate cerebellar involvement in FCMTE patients. Decreased SICI is compatible with intracortical GABAA -ergic dysfunction. Cerebellar and intracortical functional changes could result from a common mechanism such as a channelopathy. Alternatively, decreased cortical inhibition may be caused by dysfunction of the cerebello-thalamo-cortical loop as a result of primary cerebellar pathology. © 2007 Movement Disorder Society [source]

    Heritability of different measures of smooth pursuit eye tracking dysfunction: A study of normal twins

    PSYCHOPHYSIOLOGY, Issue 6 2000
    Joanna Katsanis
    Research studies have found that smooth pursuit eye movement dysfunction may serve as an index of genetic liability to develop schizophrenia. The heritability of various measures of smooth pursuit eye tracking proficiency and the saccades that occur during smooth pursuit was examined in 64 monozygotic (MZ) and 48 dizygotic (DZ) twin pairs. Two age cohorts were assessed (11,12 and 17,18 years of age). Intraclass correlations indicated significant similarity in the MZ twins for almost all measures in both age cohorts, whereas few of the DZ twin correlations attained significance. Biometrical modeling indicated that genetic mechanisms influence performance on both global and specific eye tracking measures, accounting for about 40% to 60% of the variance. These findings suggest that the underlying brain systems responsible for smooth pursuit and saccade generation during pursuit are under partial genetic control. [source]

    Ocular motor development in normal and premature children

    ACTA OPHTHALMOLOGICA, Issue 2009
    J YGGE
    The ocular motor system is immature at birth and the different types of eye movements develop at different stages of child development. This presentation aims to discuss the normal ocular motor development and the often delayed development of the ocular motor functions seen in premature children. For example, the visual fixation is often more instable in the premature child. Also the saccadic as well as the smooth pursuit and vergence systems exhibit delays in development in the premature child. The delayed development has implications for the clinical investigation and must be taken into consideration when examining the visual functions of the premature child. [source]