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Biomedical subjects

A Berthoz

Publications and source records attributed to A Berthoz.

At least 181 records · Page 10Linked to original sources
PubMed1977

[Excitatory effect of the superior colliculus on the motor neurons of extra-ocular muscles of cats].

The synaptic actions which might underline the caccadic eye movements induced by stimulation of the superior colliculus have been studied in the unanesthetized cat "encéphale isolé". Intracellular recordings of extraocular muscle medial rectus motoneurons have revealed a minimally disynaptic excitatory projection from the superior colliculus to the ipsilateral medial rectus motoneurons (latency 1.3 to 2.6 msec).

Action Potentials↗
PubMed1977

Dynamic relations between natural vestibular inputs and activity of forelimb extensor muscles in the decerebrate cat. III. Motor output during rotations in the vertical plane.

Decerebrate cats with the spinal cord sectioned at low thoracic levels were subjected to sinusoidal rotations in the vertical plane, while recording the EMG activity of both triceps brachii muscles. The applied stimulus activated utricular and saccular receptors as well as the vertical semicircular canals. Using results presented in preceding papers 2,3, namely the dynamic response characteristics of the motor output to macular inputs and the fact that the responses to otolith and canal stimulation summate linearly 3, it is deduced that the dynamic characteristics of the motor output in response to stimulation of the vertical canals are the same as those to horizontal canal stimulation. The implication of these findings vis-à-vis the problem of central processing of vestibular inputs and the problem of postural stability is discussed.

Acceleration↗
PubMed1977

Linear acceleration modifies the perceived velocity of a moving visual scene.

In the present work, we have shown the effect of a vestibular stimulation on the velocity perception of a moving scene. The intensity of this effect is related to the amplitude of the cart acceleration, image velocity, spatial frequency of the visual stimulus, and the angle between the directions of cart and image movement. A simple model has been developed to determine whether the perception of visual movement is due to the geometric projection of the vestibular evaluation on the visual vector, or the inverse.

Humans↗
PubMed1975

Perception of linear horizontal self-motion induced by peripheral vision (linearvection) basic characteristics and visual-vestibular interactions.

The basic characteristics of the sensation of linear horizontal motion have been studied. Objective linear motion was induced by means of a moving cart. Visually induced linear motion perception (linearvection) was obtained by projection of moving images at the periphery of the visual field. Image velocity and luminance thresholds for the appearance of linearvection have been measured and are in the range of those for image motion detection (without sensation of self motion) by the visual system. Latencies of onset are around 1 sec and short term adaptation has been shown. The dynamic range of the visual analyser as judged by frequency analysis is lower than for the vestibular analyser. Conflicting situations in which visual cues contradict vestibular and other proprioceptive cues show, in the case of linearvection a dominance of vision which supports the idea of an essential although not independent role of vision in self motion perception.

Adaptation, Psychological↗
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↗