We investigated a group of patients who were blind because of disease affecting the anterior visu... more We investigated a group of patients who were blind because of disease affecting the anterior visual pathways. All subjects showed an inability to maintain steady eye position, with a consequent jerk nystagmus. Blindness from birth was associated with an impaired vestibuloocular reflex and inability to voluntarily initiate saccades, although quick phases of nystagmus were maintained. Acquired blindness was associated with relatively preserved vestibulo-ocular responses and the ability to initiate voluntary saccades and smoothly track self-moved targets. Certain features of the eye movements of the blind are similar to those due to cerebellar dysfunction.
Eye movements serve the needs of our visual sense and can be classified into subtypes according t... more Eye movements serve the needs of our visual sense and can be classified into subtypes according to their specific functions. Main functions and dysfunctions are given, with an emphasis on nystagmus.
Movement disorders : official journal of the Movement Disorder Society, Jan 16, 2015
Cervical dystonia is characterized by abnormal posturing of the head, often combined with tremor-... more Cervical dystonia is characterized by abnormal posturing of the head, often combined with tremor-like oscillatory head movements. The nature and source of these oscillatory head movements is controversial, so they were quantified to delineate their characteristics and develop a hypothetical model for their genesis. A magnetic search coil system was used to measure head movements in 14 subjects with cervical dystonia. Two distinct types of oscillatory head movements were detected for most subjects, even when they were not clinically evident. One type had a relatively large amplitude and jerky irregular pattern, and the other had smaller amplitude with a more regular and sinusoidal pattern. The kinematic properties of these two types of oscillatory head movements were distinct, although both were often combined in the same subject. Both had features suggestive of a defect in a central neural integrator. The combination of different types of oscillatory head movements in cervical dysto...
Journal of vestibular research : equilibrium & orientation, 2012
Here we investigated how well internal estimates of direction of gravity are preserved over time ... more Here we investigated how well internal estimates of direction of gravity are preserved over time and if the subjective visual vertical (SVV) and horizontal (SVH) can be used inter-changeably. Fourteen human subjects repetitively aligned a luminous line to SVV, SVH or subjective visual oblique (± 45°) over 5 min in otherwise complete darkness and also in dim light. Both accuracy (i.e., the degree of veracity as reflected by the median adjustment error) and precision (i.e., the degree of reproducability as reflected by the trial-to-trial variability) of adjustments along the principle axes were significantly higher than along the oblique axes. Orthogonality was only preserved in a minority of subjects. Adjustments were significantly different between SVV vs. SVH (7/14 subjects) and between ±45° vs. -45° (12/14) in darkness and in 6/14 and 14/14 subjects, respectively, in dim light. In darkness, significant drifts over 5min were observed in a majority of trials (33/56). Both accuracy a...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2008
The rotational vestibulo-ocular reflex (rVOR) contributes to gaze stabilitization by compensating... more The rotational vestibulo-ocular reflex (rVOR) contributes to gaze stabilitization by compensating head rotational movements sensed by the semicircular canals (SCC). The CNS improves the performance of the horizontal rVOR through the so called velocity storage mechanism (VSM). However the properties of the VSM in response to pitch rotations are less well known. We recorded eye movements evoked by whole-body constant-velocity pitch rotations about an earth-horizontal, interaural axis in four healthy human subjects. Subjects were tumbled forward, and backward, at 60 deg/s for over one minute using a 3D turntable. In these conditions also the otoliths contribute to the perception of head rotation because they sense the changes in direction of the gravity vector. The vertical slow phase velocity (SPV) responses show the typical exponential decay of the rVOR and a residual, otolith-driven sinusoidal modulation with a bias. Here the estimates of the contributions coming from the otoliths a...
Saccadic oscillations are unwanted back-to-back saccades occurring one upon the other that produc... more Saccadic oscillations are unwanted back-to-back saccades occurring one upon the other that produce a high-frequency oscillation of the eyes (usually 15-30 Hz). These may occur transiently in normal subjects, for example, around the orthogonal axis of a purely horizontal or vertical saccade, during combined saccade-vergence gaze shifts or during blinks. Some subjects may produce saccadic oscillations at will, usually with convergence. Pathological, involuntary saccadic oscillations such as flutter and opsoclonus are prominent in certain diseases. Our recent mathematical model of the premotor circuit for generating saccades includes brainstem burst neurons in the paramedian pontine reticular formation (PPRF), which show the physiological phenomenon of post-inhibitory rebound (PIR). This model makes saccadic oscillations because of the positive feedback among excitatory and inhibitory burst neurons. Here we review our recent findings and hypotheses and show how they may be reproduced u...
The translational vestibulo-ocular reflex (tVOR) stabilizes an image on the fovea during linear m... more The translational vestibulo-ocular reflex (tVOR) stabilizes an image on the fovea during linear movements of the head. It has been suggested that the tVOR may share pathways with the pursuit system. We asked whether the tVOR and pursuit would be similar in their behavior relative to Listing's Law. We compared torsional eye velocity as a function of vertical orbital position during interaural translation, pursuit, and yaw-axis rotation. We found that the eye-position-dependence of torsion was similar during translation and pursuit, which differed from that during yaw-axis rotation. These findings further support a close relationship between the mechanisms that generate pursuit and the tVOR.
Vergence eye movements undergo adaptive recalibration in response to a training stimulus in which... more Vergence eye movements undergo adaptive recalibration in response to a training stimulus in which the initial disparity is changed just after vergence begins (the double-step paradigm). In the present study the changes in the dynamic properties of convergence, speed and acceleration, were examined by using this double-step paradigm, before and after adaptation. Four normal subjects participated. Three-dimensional visual stimuli were provided by a head-mounted display with two liquid crystal diode (LCD) panels. To induce adaptation, a double step of disparity was used: an initial step from distances of 2 to 1 m was followed by a second step to distances of 0.7 m ("increasing paradigm") or 1.4 m ("decreasing paradigm") after a constant period of 0.2 seconds. The dynamic properties of vergence were compared before and after 30 minutes of training with these paradigms. Peak velocity of convergence became significantly greater (increasing paradigm) or smaller (decreas...
To describe adaptive changes in torsional alignment that follow sustained cyclovergence in health... more To describe adaptive changes in torsional alignment that follow sustained cyclovergence in healthy humans. Eye movements were recorded binocularly from four healthy subjects using dual-coil scleral annuli. Cyclovergence movements were evoked over periods of 30 to 150 seconds using a stereoscopic display, presenting gratings of lines arranged horizontally, vertically, or at 45 degrees, subtending angles of up to 48 degrees. In- and excyclodisparities of 5 degrees were introduced and removed in a single-step fashion. After stimulation, the time course and magnitude of the decay in cyclovergence was compared with the subject either in darkness or viewing a baseline stimulus of zero cyclodisparity. As reported previously, the cyclovergence response to incyclodisparities was greater than to excyclodisparities. After sustained excyclovergence, however, in all subjects and in response to all orientations of the gratings, the decay in darkness was incomplete, implying an adaptive change in ...
One of the signs of the cerebellar ocular motor syndrome is the inability to maintain horizontal ... more One of the signs of the cerebellar ocular motor syndrome is the inability to maintain horizontal and vertical fixation. Typically, in the presence of cerebellar atrophy, the eyes show horizontal gaze-evoked and vertical downbeat nystagmus. We investigated whether or not the cerebellar ocular motor syndrome also includes a torsional drift and, specifically, if it is independent from the drift in the horizontal-vertical plane. The existence of such a torsional drift would suggest that the cerebellum is critically involved in maintaining the eyes in Listing's plane. Eighteen patients with cerebellar atrophy (diagnosis confirmed by magnetic resonance imaging) were tested and compared with a group of normal subjects. Three-dimensional eye movements (horizontal, vertical, and torsional) during attempted fixations of targets at different horizontal and vertical eccentricities were recorded by dual search coils in a three-field magnetic frame. The overall ocular drift was composed of an...
Drift of the eyes after saccades produces motion of images on the retina (retinal slip) that degr... more Drift of the eyes after saccades produces motion of images on the retina (retinal slip) that degrades visual acuity. In this study, we examined the contributions of proprioceptive and retinal afference to the suppression of postsaccadic drift induced by a unilateral ocular muscle paresis. Eye movements were recorded in three rhesus monkeys with a unilateral weakness of one vertical extraocular muscle before and after proprioceptive deafferentation of the paretic eye. Postsaccadic drift was examined in four visual states: monocular viewing with the normal eye (4-wk period); binocular viewing (2-wk period); binocular viewing with a disparity-reducing prism (2-wk period); and monocular viewing with the paretic eye (2-wk period). The muscle paresis produced vertical postsaccadic drift in the paretic eye, and this drift was suppressed in the binocular viewing condition even when the animals could not fuse. When the animals viewed binocularly with a disparity-reducing prism, the drift in ...
Journal of vestibular research : equilibrium & orientation, 1994
Postural stability in patients with bilateral vestibular deficits from aminoglycoside toxicity wa... more Postural stability in patients with bilateral vestibular deficits from aminoglycoside toxicity was characterized by examining their ability to use different sensory cues to maintain balance and by recording their automatic postural responses to sudden translational and rotational (pitch) perturbations of the support surface. We found our patients had increased sway on sensory tests in which either visual or somatosensory cues were altered and were unable to maintain their balance when both visual and somatosensory cues were altered compared to age-matched normal subjects. The amount of vestibular loss, as inferred from the VOR Tc, accounted for a significant amount of A-P sway on test 4 in which somatosensory cues were altered. The frequency response of anterior-posterior sway in the BVL group suggests that they use more hip movements than do normal subjects to maintain postural stability. The responses of BVL patients to sudden translations of the support surface did not differ fro...
PURPOSE. Research has shown that the orientation of the exiting wire from a scleral search coil (... more PURPOSE. Research has shown that the orientation of the exiting wire from a scleral search coil (nasal in the original coil, inferior in the modified coil) influences the pattern of torsion associated with blinks, presumably due to the upper eyelid touching the wire. The present study was conducted to inves- tigate whether coil wire orientation also influences the pattern of
1. This series of three papers aims to describe the three-dimensional, kinematic input-output rel... more 1. This series of three papers aims to describe the three-dimensional, kinematic input-output relations of the rotational vestibuloocular reflex (VOR) in humans, and to identify the functional advantages of these relations. In this first paper the response to sinusoidal rotation in darkness at 0.3 Hz, maximum speed 37.5%/s, was quantified by the use of the three-dimensional analogue of VOR gain: a 3 x 3 matrix where each element describes the dependence of one component (torsional, vertical, or horizontal) of eye velocity on one component of head velocity. 2. The three matrix elements indicating collinear gains (i.e., dependence of torsional eye velocity on torsional head velocity, vertical on vertical, and horizontal on horizontal) were smaller than the -1's required for optimal retinal image stabilization. Of these three the torsional gain was weakest: -0.37 for rotation about an earth-vertical axis, versus -0.73 and -0.64 for vertical and horizontal gains. Matrix elements ind...
We investigated a group of patients who were blind because of disease affecting the anterior visu... more We investigated a group of patients who were blind because of disease affecting the anterior visual pathways. All subjects showed an inability to maintain steady eye position, with a consequent jerk nystagmus. Blindness from birth was associated with an impaired vestibuloocular reflex and inability to voluntarily initiate saccades, although quick phases of nystagmus were maintained. Acquired blindness was associated with relatively preserved vestibulo-ocular responses and the ability to initiate voluntary saccades and smoothly track self-moved targets. Certain features of the eye movements of the blind are similar to those due to cerebellar dysfunction.
We investigated a group of patients who were blind because of disease affecting the anterior visu... more We investigated a group of patients who were blind because of disease affecting the anterior visual pathways. All subjects showed an inability to maintain steady eye position, with a consequent jerk nystagmus. Blindness from birth was associated with an impaired vestibuloocular reflex and inability to voluntarily initiate saccades, although quick phases of nystagmus were maintained. Acquired blindness was associated with relatively preserved vestibulo-ocular responses and the ability to initiate voluntary saccades and smoothly track self-moved targets. Certain features of the eye movements of the blind are similar to those due to cerebellar dysfunction.
Eye movements serve the needs of our visual sense and can be classified into subtypes according t... more Eye movements serve the needs of our visual sense and can be classified into subtypes according to their specific functions. Main functions and dysfunctions are given, with an emphasis on nystagmus.
Movement disorders : official journal of the Movement Disorder Society, Jan 16, 2015
Cervical dystonia is characterized by abnormal posturing of the head, often combined with tremor-... more Cervical dystonia is characterized by abnormal posturing of the head, often combined with tremor-like oscillatory head movements. The nature and source of these oscillatory head movements is controversial, so they were quantified to delineate their characteristics and develop a hypothetical model for their genesis. A magnetic search coil system was used to measure head movements in 14 subjects with cervical dystonia. Two distinct types of oscillatory head movements were detected for most subjects, even when they were not clinically evident. One type had a relatively large amplitude and jerky irregular pattern, and the other had smaller amplitude with a more regular and sinusoidal pattern. The kinematic properties of these two types of oscillatory head movements were distinct, although both were often combined in the same subject. Both had features suggestive of a defect in a central neural integrator. The combination of different types of oscillatory head movements in cervical dysto...
Journal of vestibular research : equilibrium & orientation, 2012
Here we investigated how well internal estimates of direction of gravity are preserved over time ... more Here we investigated how well internal estimates of direction of gravity are preserved over time and if the subjective visual vertical (SVV) and horizontal (SVH) can be used inter-changeably. Fourteen human subjects repetitively aligned a luminous line to SVV, SVH or subjective visual oblique (± 45°) over 5 min in otherwise complete darkness and also in dim light. Both accuracy (i.e., the degree of veracity as reflected by the median adjustment error) and precision (i.e., the degree of reproducability as reflected by the trial-to-trial variability) of adjustments along the principle axes were significantly higher than along the oblique axes. Orthogonality was only preserved in a minority of subjects. Adjustments were significantly different between SVV vs. SVH (7/14 subjects) and between ±45° vs. -45° (12/14) in darkness and in 6/14 and 14/14 subjects, respectively, in dim light. In darkness, significant drifts over 5min were observed in a majority of trials (33/56). Both accuracy a...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2008
The rotational vestibulo-ocular reflex (rVOR) contributes to gaze stabilitization by compensating... more The rotational vestibulo-ocular reflex (rVOR) contributes to gaze stabilitization by compensating head rotational movements sensed by the semicircular canals (SCC). The CNS improves the performance of the horizontal rVOR through the so called velocity storage mechanism (VSM). However the properties of the VSM in response to pitch rotations are less well known. We recorded eye movements evoked by whole-body constant-velocity pitch rotations about an earth-horizontal, interaural axis in four healthy human subjects. Subjects were tumbled forward, and backward, at 60 deg/s for over one minute using a 3D turntable. In these conditions also the otoliths contribute to the perception of head rotation because they sense the changes in direction of the gravity vector. The vertical slow phase velocity (SPV) responses show the typical exponential decay of the rVOR and a residual, otolith-driven sinusoidal modulation with a bias. Here the estimates of the contributions coming from the otoliths a...
Saccadic oscillations are unwanted back-to-back saccades occurring one upon the other that produc... more Saccadic oscillations are unwanted back-to-back saccades occurring one upon the other that produce a high-frequency oscillation of the eyes (usually 15-30 Hz). These may occur transiently in normal subjects, for example, around the orthogonal axis of a purely horizontal or vertical saccade, during combined saccade-vergence gaze shifts or during blinks. Some subjects may produce saccadic oscillations at will, usually with convergence. Pathological, involuntary saccadic oscillations such as flutter and opsoclonus are prominent in certain diseases. Our recent mathematical model of the premotor circuit for generating saccades includes brainstem burst neurons in the paramedian pontine reticular formation (PPRF), which show the physiological phenomenon of post-inhibitory rebound (PIR). This model makes saccadic oscillations because of the positive feedback among excitatory and inhibitory burst neurons. Here we review our recent findings and hypotheses and show how they may be reproduced u...
The translational vestibulo-ocular reflex (tVOR) stabilizes an image on the fovea during linear m... more The translational vestibulo-ocular reflex (tVOR) stabilizes an image on the fovea during linear movements of the head. It has been suggested that the tVOR may share pathways with the pursuit system. We asked whether the tVOR and pursuit would be similar in their behavior relative to Listing's Law. We compared torsional eye velocity as a function of vertical orbital position during interaural translation, pursuit, and yaw-axis rotation. We found that the eye-position-dependence of torsion was similar during translation and pursuit, which differed from that during yaw-axis rotation. These findings further support a close relationship between the mechanisms that generate pursuit and the tVOR.
Vergence eye movements undergo adaptive recalibration in response to a training stimulus in which... more Vergence eye movements undergo adaptive recalibration in response to a training stimulus in which the initial disparity is changed just after vergence begins (the double-step paradigm). In the present study the changes in the dynamic properties of convergence, speed and acceleration, were examined by using this double-step paradigm, before and after adaptation. Four normal subjects participated. Three-dimensional visual stimuli were provided by a head-mounted display with two liquid crystal diode (LCD) panels. To induce adaptation, a double step of disparity was used: an initial step from distances of 2 to 1 m was followed by a second step to distances of 0.7 m ("increasing paradigm") or 1.4 m ("decreasing paradigm") after a constant period of 0.2 seconds. The dynamic properties of vergence were compared before and after 30 minutes of training with these paradigms. Peak velocity of convergence became significantly greater (increasing paradigm) or smaller (decreas...
To describe adaptive changes in torsional alignment that follow sustained cyclovergence in health... more To describe adaptive changes in torsional alignment that follow sustained cyclovergence in healthy humans. Eye movements were recorded binocularly from four healthy subjects using dual-coil scleral annuli. Cyclovergence movements were evoked over periods of 30 to 150 seconds using a stereoscopic display, presenting gratings of lines arranged horizontally, vertically, or at 45 degrees, subtending angles of up to 48 degrees. In- and excyclodisparities of 5 degrees were introduced and removed in a single-step fashion. After stimulation, the time course and magnitude of the decay in cyclovergence was compared with the subject either in darkness or viewing a baseline stimulus of zero cyclodisparity. As reported previously, the cyclovergence response to incyclodisparities was greater than to excyclodisparities. After sustained excyclovergence, however, in all subjects and in response to all orientations of the gratings, the decay in darkness was incomplete, implying an adaptive change in ...
One of the signs of the cerebellar ocular motor syndrome is the inability to maintain horizontal ... more One of the signs of the cerebellar ocular motor syndrome is the inability to maintain horizontal and vertical fixation. Typically, in the presence of cerebellar atrophy, the eyes show horizontal gaze-evoked and vertical downbeat nystagmus. We investigated whether or not the cerebellar ocular motor syndrome also includes a torsional drift and, specifically, if it is independent from the drift in the horizontal-vertical plane. The existence of such a torsional drift would suggest that the cerebellum is critically involved in maintaining the eyes in Listing's plane. Eighteen patients with cerebellar atrophy (diagnosis confirmed by magnetic resonance imaging) were tested and compared with a group of normal subjects. Three-dimensional eye movements (horizontal, vertical, and torsional) during attempted fixations of targets at different horizontal and vertical eccentricities were recorded by dual search coils in a three-field magnetic frame. The overall ocular drift was composed of an...
Drift of the eyes after saccades produces motion of images on the retina (retinal slip) that degr... more Drift of the eyes after saccades produces motion of images on the retina (retinal slip) that degrades visual acuity. In this study, we examined the contributions of proprioceptive and retinal afference to the suppression of postsaccadic drift induced by a unilateral ocular muscle paresis. Eye movements were recorded in three rhesus monkeys with a unilateral weakness of one vertical extraocular muscle before and after proprioceptive deafferentation of the paretic eye. Postsaccadic drift was examined in four visual states: monocular viewing with the normal eye (4-wk period); binocular viewing (2-wk period); binocular viewing with a disparity-reducing prism (2-wk period); and monocular viewing with the paretic eye (2-wk period). The muscle paresis produced vertical postsaccadic drift in the paretic eye, and this drift was suppressed in the binocular viewing condition even when the animals could not fuse. When the animals viewed binocularly with a disparity-reducing prism, the drift in ...
Journal of vestibular research : equilibrium & orientation, 1994
Postural stability in patients with bilateral vestibular deficits from aminoglycoside toxicity wa... more Postural stability in patients with bilateral vestibular deficits from aminoglycoside toxicity was characterized by examining their ability to use different sensory cues to maintain balance and by recording their automatic postural responses to sudden translational and rotational (pitch) perturbations of the support surface. We found our patients had increased sway on sensory tests in which either visual or somatosensory cues were altered and were unable to maintain their balance when both visual and somatosensory cues were altered compared to age-matched normal subjects. The amount of vestibular loss, as inferred from the VOR Tc, accounted for a significant amount of A-P sway on test 4 in which somatosensory cues were altered. The frequency response of anterior-posterior sway in the BVL group suggests that they use more hip movements than do normal subjects to maintain postural stability. The responses of BVL patients to sudden translations of the support surface did not differ fro...
PURPOSE. Research has shown that the orientation of the exiting wire from a scleral search coil (... more PURPOSE. Research has shown that the orientation of the exiting wire from a scleral search coil (nasal in the original coil, inferior in the modified coil) influences the pattern of torsion associated with blinks, presumably due to the upper eyelid touching the wire. The present study was conducted to inves- tigate whether coil wire orientation also influences the pattern of
1. This series of three papers aims to describe the three-dimensional, kinematic input-output rel... more 1. This series of three papers aims to describe the three-dimensional, kinematic input-output relations of the rotational vestibuloocular reflex (VOR) in humans, and to identify the functional advantages of these relations. In this first paper the response to sinusoidal rotation in darkness at 0.3 Hz, maximum speed 37.5%/s, was quantified by the use of the three-dimensional analogue of VOR gain: a 3 x 3 matrix where each element describes the dependence of one component (torsional, vertical, or horizontal) of eye velocity on one component of head velocity. 2. The three matrix elements indicating collinear gains (i.e., dependence of torsional eye velocity on torsional head velocity, vertical on vertical, and horizontal on horizontal) were smaller than the -1's required for optimal retinal image stabilization. Of these three the torsional gain was weakest: -0.37 for rotation about an earth-vertical axis, versus -0.73 and -0.64 for vertical and horizontal gains. Matrix elements ind...
We investigated a group of patients who were blind because of disease affecting the anterior visu... more We investigated a group of patients who were blind because of disease affecting the anterior visual pathways. All subjects showed an inability to maintain steady eye position, with a consequent jerk nystagmus. Blindness from birth was associated with an impaired vestibuloocular reflex and inability to voluntarily initiate saccades, although quick phases of nystagmus were maintained. Acquired blindness was associated with relatively preserved vestibulo-ocular responses and the ability to initiate voluntary saccades and smoothly track self-moved targets. Certain features of the eye movements of the blind are similar to those due to cerebellar dysfunction.
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Papers by David Zee