[Cooperation and substitution of the saccadic system and the reflexes of vestibular origin: should the "reflex" concept be revised?].
Neuronal mechanisms of production of ocular saccadic movements are discussed, together with stabilizing movements of vestibular origin, and descriptions given of several neuronal elements constituting the tecto-reticulo-spinal system, the generator of horizontal saccadic movements in the brain stem, the vestibulo-ocular pathway, etc... Analysis of these pathways and of the signals travelling through them suggests that the overall apparatus is not constituted of isolated reflex modules but acts as a true functional unit for cooperation between orientation and stabilization mechanisms. In addition, coordination of synergies between eye and head movements appear to be based on the activity of clearly identifiable neurons. This neuronal implementation of the concept of synergy is completed further by a remarkable functional flexibility. The latter allows substitution by the brain, for example, fo saccades instead of vestibular reflex movements when the latter are deficient because of lesions or disturbances in the coherence of sensory information. The principal conclusion reached is that cognitive factors, which imply representations of body movements in space activated as a function of the subject's goals, must be considered when ocular movement, and gaze control is described.
Berthoz
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Laboratoire de Physiologie Neurosensorielle du C.N.R.S., Paris, France
D000818:Animals; D002415:Cats; D005133:Eye Movements / Q000502:physiology*; D009949:Orientation; D004856:Postural Balance / Q000502:physiology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D014795:Visual Pathways
Coopération et substitution entre le système saccadique et les "réflexes" d'origine vestibulaire: faut-il réviser la notion de "réflexe"?