Three-, Rather Than Two-Dimensional Burst Generation for Spontaneous Saccadic Eye Movements
Michael Fetter, Thomas Haslwanter, Hubert Misslisch, Douglas Tweed in Three-Dimensional Kinematics of Eye, Head and Limb Movements, 2020
Throughout this paper, saccadic eye movements are described by the displacement vector, . For eye position vectors out of Listing’s plane, is a 3D vector. As was shown by Hepp et al. (1993), the displacement vector in Listing’s plane, , corresponds to the retinal error vector, in good approximation, for eccentricities up to about 25 deg. An alternative description of a saccade is given by the single-axis rotation, , that carries the eye from to . Up to third order in the saccade amplitude: .
Cognition, Language and Intelligence
Rolland S. Parker in Concussive Brain Trauma, 2016
Effective selective attention, in the presence of distractors, implies allocation of attentional resources to target detection. The effects of selective attention are observed at all levels of central nervous system (CNS) processing, becoming stronger as one moves more rostrally. Readiness to respond interacts with selective attention. This is the result of a choice (set) or an environmental demand, in which attention is concentrated on particular stimuli from among others. The sensory modalities do not function independently; there are limited attentional resources for processing information across sensory systems (Hsaio & Vega-Bermudez, 2002). Sensory processing may have a limited capacity to carry out more than one cognitive or perceptual task at a time. Attention mediates this selection. Saccade planning and visual attention activate centers of the frontal eye fields of the PFC, lateral area, and the superior colliculus. Exogenous (stimulus-driven) attention focuses upon salient, potentially important events. Endogenous attention focuses upon internally defined goals and against external distractions.
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
Conjugate ocular movements which serve to maintain stability of GAZE. PURSUIT EYE MOVEMENTS and SACCADES are the most extensively studied by psychologists. Pursuit eye movements are driven by slow- to medium-velocity visual targets and can be controlled by the (motion-sensitive) EXTRASTRIATE CORTEX. LESIONS to these regions may temporarily or permanently disrupt smooth pursuit while leaving saccades unaffected. Saccadic eye movements are extremely rapid and are associated with perceptual suppression during the high velocity portion of the movement. Posterior PARIETAL CORTEX and the FRONTAL EYE FIELDS are part of two parallel, semi- independent channels which play a role in voluntary saccades.
Neuro-ophthalmology of movement disorders
Published in Expert Review of Ophthalmology, 2018
Some ocular signs are associated with only certain SCAs and can assist in differential diagnosis [54,56]. Although nearly all cerebellar ataxias have abnormalities in saccadic eye movements, the following SCAs have been associated with nystagmus: 1,2,5,6,8,10,11,12,18, and 28. Rebound nystagmus, supranuclear ophthalmoparesis, decreased blink rate, lid retraction, and impaired vestibulo-ocular reflex gain are typically present in SCA3. Impaired smooth pursuit, downbeat nystagmus are frequent findings in SCA6. Pigmentary macular degeneration is a characteristic ophthalmologic feature of SCA7 but it was also reported in some patients with SCA2, SCA6, and adult onset Refsum disease (autosomal recessive peroxisomal disease manifesting as cerebellar ataxia, peripheral neuropathy and visual disturbance) [57–59]. Ocular signs of Friedreich ataxia, the most common autosomal recessive ataxia, include saccadic intrusions (square-wave jerks or ocular flutter), decreased vestibular-ocular reflex gain, gaze evoked and rebound nystagmus, decreased visual acuity, thinning of retinal nerve fiber layer [54].
Evaluation of saccadic velocity in patients with orbital floor fracture before and after surgery
Published in Seminars in Ophthalmology, 2022
Ken Kakeue, Masanobu Kanazawa, Tatsuya Yunoki, Miharu Mihara, Atsushi Hayashi
Saccadic eye movement was recorded using the ViewPoint EyeTracker® system (Arrington Research, Scottsdale, AZ, USA) at a sampling rate of 350 Hz. This system consists of two infrared cameras mounted on the head positioner, which sends images of the eye to a computer via a USB cable. The eye tracker records the eye positions using the dark-pupil technique. The patient sat on a chair in front of a table with his or her head stabilized in a head positioner. A computer monitor (Diamondcrysta®, RDT222WM-S, Mitsubishi, Tokyo) displaying the target was located 40 cm from the patient’s eyes. Prior to the measurement of saccadic eye movement, a 9-point grid (3 × 3 matrix) calibration and a subsequent validation procedure were performed for each patient using software supplied by the eye-tracker manufacturer (ViewPoint EyeTracker Software User Guide).
Spatial neglect treatment: The brain’s spatial-motor Aiming systems
Published in Neuropsychological Rehabilitation, 2022
A. M. Barrett, Kelly M. Goedert, Alexandre R. Carter, Amit Chaudhari
Damage to subcortical structures has also been associated with spatial Aiming bias. In the same study of the neural correlates of directional hypokinesia that implicated frontal lobe regions, Sapir et al. (2007) also reported a strong association of this bias with damage of the ventral lateral putamen and claustrum, and speculated that this might result in a disruption of subcortical dopaminergic neurotransmission which can play an important role in spatial cognition as discussed above (Sapir et al., 2007). Another subcortical structure, the mammalian superior colliculus (SC) is a major hub of sensorimotor integration and neurons in deep layers of the SC are crucial to the generation of contraversive saccadic eye movements (Robinson, 1972). In addition, the SC has other motoric functions (Gandhi & Katnani, 2011), including multiple classes of neurons that are active prior to and during arm movements, and which may contribute to the control of visually-guided movements (Lunenburger et al., 2001).
Related Knowledge Centers
- Blinking
- Eye Movement
- Fixation
- Fovea Centralis
- Frontal Eye Fields
- Rapid Eye Movement Sleep
- Retina
- Smooth Pursuit
- Superior Colliculus
- Optokinetic Response