Jean Laurens

24 février 2012

Washington University School of Medicine, Saint Louis, Missouri, USA

Neural representation of head motion in the vestibulo-cerebellum of the macaque

Invité par Laurent Goffart

Spatial orientation, locomotion and equilibrium rely on the brain’s ability to estimate head orientation relative to gravity. Studying this function provides an excellent model of how the brain tracks the motion of more complex body parts such as the arms, a process in which the cerebellum plays a key role. The otoliths, which are gravity sensors located in the inner ear, are also sensitive to head translations : they detect the gravito-inertial force, which is the sum of gravity and linear acceleration. As an analogy, one can compare them to a pendulum, swinging relative to the head when it tilts or accelerates. Behavioral studies suggest that the brain resolves this ambiguity by using an internal model of head motion. This model integrates over time head rotation signals provided by the semi-circular canals and allows maintaining an internal estimate of the orientation of the gravity vector relative to the head (g) which is subtracted from the otolith signal to compute an internal estimate of acceleration. In support of this theory, we have identified populations of cells which selectively encode head translations and head tilt in the vestibulo-cerebellum of the macaque monkey. We will review the characteristics of these cells by presenting their responses to a panel of motion paradigms which address various aspects of vestibular information processing.
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