PubMed Health⌕ Search

Biomedical subjects

D Guitton

Publications and source records attributed to D Guitton.

50 records · Page 3Linked to original sources
PubMed1984

Eye-head coordination in cats.

Gaze is the position of the visual axis in space and is the sum of the eye movement relative to the head plus head movement relative to space. In monkeys, a gaze shift is programmed with a single saccade that will, by itself, take the eye to a target, irrespective of whether the head moves. If the head turns simultaneously, the saccade is correctly reduced in size (to prevent gaze overshoot) by the vestibuloocular reflex (VOR). Cats have an oculomotor range (OMR) of only about +/- 25 degrees, but their field of view extends to about +/- 70 degrees. The use of the monkey's motor strategy to acquire targets lying beyond +/- 25 degrees requires the programming of saccades that cannot be physically made. We have studied, in cats, rapid horizontal gaze shifts to visual targets within and beyond the OMR. Heads were either totally unrestrained or attached to an apparatus that permitted short unexpected perturbations of the head trajectory. Qualitatively, similar rapid gaze shifts of all sizes up to at least 70 degrees could be accomplished with the classic single-eye saccade and a saccade-like head movement. For gaze shifts greater than 30 degrees, this classic pattern frequently was not observed, and gaze shifts were accomplished with a series of rapid eye movements whose time separation decreased, frequently until they blended into each other, as head velocity increased. Between discrete rapid eye movements, gaze continued in constant velocity ramps, controlled by signals added to the VOR-induced compensatory phase that followed a saccade. When the head was braked just prior to its onset in a 10 degrees gaze shift, the eye attained the target. This motor strategy is the same as that reported for monkeys. However, for larger target eccentricities (e.g., 50 degrees), the gaze shift was interrupted by the brake and the average saccade amplitude was 12-15 degrees, well short of the target and the OMR. Gaze shifts were completed by vestibularly driven eye movements when the head was released. Braking the head during either quick phases driven by passive head displacements or visually triggered saccades resulted in an acceleration of the eye, thereby implying interaction between the VOR and these rapid-eye-movement signals. Head movements possessed a characteristic but task-dependent relationship between maximum velocity and amplitude. Head movements terminated with the head on target. The eye saccade usually lagged the head displacement.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1981

Task dependent variations of ocular lateropulsion in Wallenberg's syndrome.

The eye movements of a patient with a left lateral medullary infarct (Wallenberg's syndrome) were recorded using the scleral search coil in magnetic field technique. When asked to look at spontaneously appearing targets, saccades to the left were generally accurate but those to the right reached the target by multiple step refixation saccades. Large amplitude rightward saccades were possible between two continuously visible targets or when making voluntary saccades in the dark. Vertical saccades, up or down, between spontaneously appearing targets were always associated with a leftward eye movement (lateropulsion). Voluntary vertical saccades between continuously visible targets showed that upward movements had left lateropulsion but downward movements were normal. Vertical voluntary saccades in the dark were oblique, upward saccades showing left lateropulsion and downward saccades rightward deviation. The aberrant horizontal components of normal oblique saccades. Possibly impaired assessment of verticality with incorrect eye position information produced by the infarct accounts for the lateropulsion in saccades in Wallenberg's syndrome.

Aged↗
PubMed1981

[A comparison between orienting rapid eye movements accompanying active or passive head movement in the cat].

Gaze is shifted by means of eye saccades which, in most instances, are synchronized with head rotations. During eye-head movements performed by cats in the dark, most of the rapid eye movements start after the head has begun to move (mean time lag was 45 msec). This pattern resembles that observed when the cat, as a whole, is suddenly rotated passively and consists of a short lasting vestibularly induced slow phase component followed by a rapid eye movement that takes the eye in the same direction as the head. We have compared the passively and actively induced eye-head movements. The rapid eye movements are similar in both cases in that they terminate at a fixed position ("goal") in the orbit irrespective of the eye's starting position. They differ primarily in the fact that the eccentricity of the "goal" during active head rotations increases much more rapidly with velocity than it does during the passive condition. The results suggest that the rapid eye movement that accompanies an active head movement in the dark is not simply a vestibularly induced quick phase.

Animals↗
PubMed1980

Stimulation of the superior colliculus in the alert cat. I. Eye movements and neck EMG activity evoked when the head is restrained.

Electrical stimulation of the cat superior colliculus (SC), in conjunction with the accurate measurement of elicited eye movements and histologically verified electrode positions, has revealed a striking antero-posterior variation in collicular organization. Three zones could be defined in the SC on the basis of eye movement patterns and associated neck muscle EMG activity evoked from the deeper layers. The Anterior zone was coextensive with the central 25 degrees of the visual retinotopically coded map contained in the superficial layers. Saccades evoked from this zone were also retinotopically coded, and the latency of EMG activity depended on the position of the eye in the orbit. A similar observation applies to the entire monkey SC. The Intermediate zone was coextensive with the 25 degrees--70 degrees of visual projections. Saccades evoked from this region were "goal-directed" and were associated with invariant, short latency EMG responses. The Posterior zone was found in the extreme caudo-lateral portion of the SC. Eye movements evoked from this zone were centering saccades associated with constant latency EMG activity. The present results in conjunction with previously demonstrated antero-posterior variations in projections to the SC, suggest that the motor strategies controlling gaze shifts toward visual targets vary depending on the location of the target in the visual field.

Animals↗
PubMed1980

Stimulation of the superior colliculus in the alert cat. II. Eye and head movements evoked when the head is unrestrained.

Electrical stimulation of the superior colliculus (SC) in alert cats free to move their head, evoked coordinate eye and head movements. The characteristics of these movements as well as their mode of coordination differed according to the collicular region being explored. Three zones were distinguished. In the anterior zone, evoked eye saccades were retinotopic and the accompanying head movements were slow and small in amplitude. The vestibular slow phase velocity signal was continuously added to the eye saccadic command so that the evoked gaze shift was identical, with the head fixed or free. In the intermediate zone, evoked eye saccades were goal-directed and the synchronous head movements fast and of large amplitude. The vestibular slow phase signal was cancelled during the eye saccade so that the evoked gaze shift was the result of the eye plus head angular displacement. In the posterior zone, the evoked head movements were goal-directed. The pattern of eye movements was similar to a vestibular nystagmus. This zone probably directly commands body orienting movements. A model of SC function in gaze orienting behavior is proposed, calling upon at least two different modes of eye-head coordination.

Animals↗
PubMed1980

Giant axonal neuropathy: visual and oculomotor deficits.

Giant axonal neuropathy, a generalised disorder or neurofilaments, presents as a chronic, progressive peripheral neuropathy in childhood. Evidence for central nervous system involvement is demonstrated in this study of four male patients with giant axonal neuropathy who had defective visual function and abnormal ocular motility. The visual system was studied by electroretinography, which showed normal retinal function, and by visual evoked potentials, which showed disease of both optic nerves and retrochiasmal visual pathways. The ocular motility disorder, studied by electrooculography, comprised defective pursuit, inability to maintain eccentric gaze with gaze paretic and rebound nystagmus, abnormal optokinetic responses and failure of suppression of the vestibulo-ocular reflex by fixation. These findings suggested involvement by giant axonal neuropathy of the cerebellar and brain stem pathways important in the control of ocular motility.

Axons↗
PubMed1980

Sialidosis: the cherry-red spot--myoclonus syndrome.

The sialidoses are a group of storage disorders of autosomal recessive inheritance in which there is a deficiency of lysosomal neuraminidase (sialidase) activity and associated sialyloligosacchariduria. Patients with one type of sialidosis may present initially to the ophthalmologist because of a cherry-red spot at the macula. In most of these patients progressive neurologic deficits ultimately develop; myoclonus is a prominent feature. A patient with the so-called cherry-red spot--myoclonus syndrome is described who had a marked deficit of the ocular smooth pursuit system, with consequent nystagmus. His visual system was normal clinically and electrophysiologically despite the obvious storage in the retinal ganglion cells.

Child↗
PubMed1979

Oculomotor abnormalities in Friedreich's ataxia.

A clinical neuro-ophthalmological and electro-oculographic study was made on fourteen patients with Friedreich's ataxia. None had evidence of optic nerve dysfunction. No patient complained of oscillopsia although all had ocular motor deficits of varying degrees, which appeared to be related to the severity of the general manifestations of the disease. The defects comprised square wave jerks, jerky pursuit with inability to maintain eccentric gaze resulting in gaze paretic nystagmus and rebound nystagmus. There was failure to suppress by fixation the vestibulo-ocular reflex. The slow phase velocity of caloric nystagmus was always of reduced velocity. There was inability to augment the slow phase velocity of optokinetic nystagmus with increasing stimulus velocity. Abnormalities of the saccadic system were manifest particularly as hypermetria. These signs in combination are suggestive of disease involving the cerebellar flocculus and vermis or their brain stem connections. No abnormalities were found in 17 parents or siblings.

Adolescent↗
PubMed1978

Frontal 'oculomotor" area in alert cat. I. Eye movements and neck activity evoked by stimulation.

(1) Stimulation within cat frontal lobe elicited saccadic eye movements whose maximum velocity was significantly greater than that of normal spontaneous saccades. (2) The majority (90%) of stimulated cortical points yielded eye movements whose directions and amplitudes were independent of the position of the eye in the orbit. The direction of these eye movements depended on the site being stimulated, with a discrete and orderly representation of directions existing within the cortex. (3) A lesser number of cortical points (10%) yielded centering movements whose directions and amplitudes depended on the position of the eye in the orbit, rather than on the site being stimulated. (4) Evoked neck muscle activation frequently preceded evoked eye movements by some 15--30 msec. This timing was compatible with a coordinated head-eye orientating response. (5) On the basis of the directions, and the latencies, of evoked eye movements, the cat frontal oculomotor area could be divided into two subregions, a 'medial' and a 'lateral', (6) The 'medial' area included the mesial wall of the hemisphere with a portion of the lower lip of the cruciate sulcus, and the medial wall of the presylvian sulcus. This area yielded contraversive eye movements with shorter latencies (average 45 msec). (7) The 'lateral' area included primarily the lateral wall of the presylvian sulcus. It yielded predominantly centering eye movements, and ipsiversive movements with longer latencies (65 msec). (8) The functional characteristics of the 'medial' area, as revealed by focal stimulation, resembled those of the monkey frontal eye field.

Animals↗
PubMed1978

Frontal 'oculomotor' area in alert cat. II. Unit discharges associated with eye movements and neck muscle activity.

(1) Unit activity in front 'oculomotor' cortex was recorded extracellularly from sites where subsequent electrical stimulation, using threshold current (50 microamperes), could elicit both eye movements and simultaneous neck EMG acitivity. (2) Of 103 cells, 19% were related to either eye movements or neck EMG activity. Cells could be grouped into three categories: (a) Directional (D) cells (31%) discharged before and during saccadic eye movements, whenever the eyes followed a target in one specific direction. Spontaneous saccades, or vestibularly driven nystagmus, in either the light or dark, elicited no responses. (b) Conditionally directional (CD) cells (43%) discharged following (i) tracking saccades; (ii) spontaneous saccades and (iii) the quick phase of nystagmus, in all directions. There usually was a slight discharge preference for one given direction, and this preference was enhanced whenever visual tracking was restricted to the preferred direction. One-third of CD cells responded to stimulation of the contralateralal biventer cervicis neck muscle (min lat. 20 msec). (c) Neck EMG (N) cells (26%) discharged in association with, and preceding, changes in neck muscle activity. These cells also responded to stimulation of the contralateral biventer cervicis muscle (min lat. 10 msec). (3) For points in the lateral 'oculomotor' region (as defined by stimulation: see ref. 17), the directions of evoked saccades, and the directions of spontaneous saccades associated with unit discharges, were sililar. In the medial region 17, the directions of evoked saccades were roughly opposite to the directions of spontaneous eye movements favoured by unit discharges.

Action Potentials↗