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Biomedical subjects

M Jeannerod

Publications and source records attributed to M Jeannerod.

At least 109 records · Page 6Linked to original sources
PubMed1979

Plasticity of the vestibulo-ocular reflex.

The plasticity of the vestibulo-ocular reflex (VOR) was investigated by examining three different processes, namely vestibular habituation to repeated head angular velocity steps, vestibular compensation after hemilabyrinthectomy, and vestibular compensation in patients suffering from unilateral Ménière's disease. The first two processes were examined in the cat, while the third process was studied in man. A quantification of these processes was obtained by computing some parameters characterizing the diagrams of the slow cumulative eye position (SCEP) and the slow phase eye velocity (SPEV) or by using the nystagmic responses to identify the main parameters of VOR. Finally, an attempt was made to interpretate the plasticity of VOR in terms of a multilevel hierarchical organization of the system controlling vestibularly induced eye movements.

Animals↗
PubMed1977

Compensation of postural effects of hemilabyrinthectomy in the cat. A sensory substitution process?

A photographic technique was used to study the evolution of lateral head-tilt following hemilabyrinthectomy in adult cats. Animals were maintained post-operatively in normally lit conditions (LM cats), in total darkness (DM cats), or in stroboscopic light. In LM casts, the head tilt peaked at 45 degrees (with the lesionned side down) on the second post-operative day, and decreased to about 0 degree within about 10 days. This evolution was followed by rebounds of head-tilt to large angles before a stable compensated head postion could be maintained (approximately at the end of the third post-operative month). In DM cats the head remained tilted by a large angle throughout the duration of the dark period. Re-exposure to light was followed by a rapid decrease of head-tilt. In stroboscopic light, the evolution of head-tilt was found to be closely similar to that in the normally lit condition. Finally, when put back in the dark at a late post-operative stage, already compensated animals were found to loose their symmetrical head position, and to re-acquire a strong head tilt. This effect resumed on re-exposure to light. It is inferred that static visual input is a necessary condition for compensation of the postural deficits of hemi-labyrinthctomy in the cat. Maintenance of a stable head posture also depends upon continuous availability of visual input.

Animals↗
PubMed1977

Developmental constraints of motion detection mechanisms in the kitten.

The influence of deprivation procedures on the development of motion detection mechanisms has been studied in twenty-two kittens. Superior colliculus neurons did not acquire direction selectivity and normal ocular dominance in animals reared in the dark or in stroboscopic light; Neuron immaturity persisted in spite of a five week additional recovery period in normal conditions. Exposure to unidirectional visual motion for 10 h during the fifth week ofpostnatal age produced an asymmetric development of the two superior colliculi. Finally, unilateral neonatal ablation of visual cortex permanently impaired development of the ipsilateral superior colliculus. In the same or in different animals, development of optokinetic nystagmus, a typical visuomotor response, was similarly influenced by the global or selective deprivation procedures. These results suggest that motion detection mechanisms (both afferent and efferent) strongly depend upon constraints imposed by the visual world during the first weeks of life.

Age Factors↗
PubMed1977

Spatial localization with paralyzed eye muscles.

Four subjects suffering from a unilateral peripheral paralysis of the 3rd or the 6th nerves have been studied in spatial localization tasks, with their normal eye occluded. When peripheral targets were presented in the hemifield corresponding to the paralysis, the saccadic eye movements (recorded from the normal occluded eye) were of an exaggerated amplitude. 'Staircase' oculomotor patterns, closely similar to those occurring in 'open-loop' visual stimulation, could also be observed. Our patients also presented the classical hypermetric misreaching when attempting to point by hand at visual targets in an otherwise dark room. This effect (past-pointing) was likely to be due to a monitoring of the exaggerated oculomotor signal: in one subject past-pointing disappeared when reaching at the targets on the basis of the sole retinal cues. Finally, the classically described illusory visual effects of ocular paralysis were limited to a feeling of instability during self-motion.

Abducens Nerve↗
PubMed1975

Development of vestibulo-ocular responses in visually deprived kittens.

The vestibular system contributes to the stabilisation of visual images on the retina by means of vestibulo-ocular compensatory reactions. The development of vestibular control of eye movements has been studied in twelve week old kittens, reared in total darkness, which have been compared with a control group of kittens reared in normal conditions. Postrotatory nystagmus, nystagmus during sinusoidal oscillations, visual suppression of vestibular nystagmus by fixation and pathological mystagmus following hemilabyrinthectomy, have been used as indicators of the functional state of the vestibulo-ocular control system. The results shown that most of the essential features of this control are present in dark-reared kittens. However, differences have been noted which possibly concern precise regulation of compensatory movements and head-eye coordination. The frequency of vestibular nystagmus is much smaller and the initial deviation of post-rotatory nystagmus in the direction of the change of movement is weak or absent in dark-reared kittens. Habituation also seems to operate differently in the two groups of kittens. Visual suppression of vestibular nystagmus is present, however, showing that an important part of the neuronal basis for visual-vestibular interaction has developed.

Animals↗
PubMed1975

[Is visual experience necessary for the maturation of vestibular control of eye movement].

The vestibular system contributes to the stabilisation of visual images on the retina by means of vestibulo-ocular compensatory reactions. The development of vestibular control of eye movements has been studied in twelve week old kittens, reared in total darkness, which have been compared with a control group of kittens reared in normal conditions. Post-rotatory nystagmus, nystagmus during sinusoidal oscillations, visual suppression of vestibular nystagmus by fixation, have been used as indicators of the functional state of the vestibulo-ocular control system. The results show that most of the essential features of this control are present in dark-reared kittens. However differences have been noted which possibly concern precise regulation of compensatory movements and head-eye coordination. The frequency of vestibular nystagmus is much smaller in dark-reared animals and the initial deviation of post rotatory nystagmus in the direction of the change of movement is absent in dark-reared kittens. Habituation also seems to operate differently in the two groups of kittens. Visual suppression of vestibular nystagmus is present.

Acceleration↗
PubMed1975

Eye movement related activity in the visual cortex of dark-reared kittens.

Kittens reared in total darkness from birth were found to be behaviorally blind, when tested at the age of 15-20 weeks. Visual cortex EEGs were recorded with transcortical electrodes. During waking, potentials related to saccadic eye movements (EMP's) were present in the dark, though they were depressed in amplitude in the light. During paradoxical sleep, rapid eye movements, isolated or in bursts, were present at a normal rate, as were occipital waves related to ponto-geniculo-occipital activity. It is concluded that EMPs during waking and phasic bursts during paradoxical sleep represent central "built in" events uninfluenced by visual experience.

Animals↗