Context contingent signal processing in the cerebellar flocculus and ventral paraflocculus during gaze saccades. 2004

T Belton, and R A McCrea
Dept. Neurobiology, Pharmacology and Physiology, University of Chicago, 5830 S. Ellis Ave., MC 0926, Chicago, IL 60637, USA. tbelton2@uchicago.edu

The vestibuloocular reflex (VOR) functions to stabilize gaze when the head moves. The flocculus region (FLR) of the cerebellar cortex, which includes the flocculus and ventral paraflocculus, plays an essential role in modifying signal processing in VOR pathways so that images of interest remain stable on the retina. In squirrel monkeys, the firing rate of most FLR Pk cells is modulated during VOR eye movements evoked by passive movement of the head. In this study, the responses of 48 FLR Purkinje cells, the firing rates of which were strongly modulated during VOR evoked by passive whole body rotation or passive head-on-trunk rotation, were compared to the responses generated during compensatory VOR eye movements evoked by the active head movements of eye-head saccades. Most (42/48) of the Purkinje cells were insensitive to eye-head saccade-related VOR eye movements. A few (6/48) generated bursts of spikes during saccade-related VOR but only during on-direction eye movements. Considered as a population FLR Pk cells were <5% as responsive to the saccade-related VOR as they were to the VOR evoked by passive head movements. The observations suggest that the FLR has little influence on signal processing in VOR pathways during eye-head saccade-related VOR eye movements. We conclude that the image-stabilizing signals generated by the FLR are highly dependent on the behavioral context and are called on primarily when external forces unrelated to self-generated eye and head movements are the cause of image instability.

UI MeSH Term Description Entries
D009038 Motion Physical motion, i.e., a change in position of a body or subject as a result of an external force. It is distinguished from MOVEMENT, a process resulting from biological activity. Motions
D011689 Purkinje Cells The output neurons of the cerebellar cortex. Purkinje Cell,Purkinje Neuron,Purkyne Cell,Cell, Purkinje,Cell, Purkyne,Cells, Purkinje,Cells, Purkyne,Neuron, Purkinje,Neurons, Purkinje,Purkinje Neurons,Purkyne Cells
D012027 Reflex, Vestibulo-Ocular A reflex wherein impulses are conveyed from the cupulas of the SEMICIRCULAR CANALS and from the OTOLITHIC MEMBRANE of the SACCULE AND UTRICLE via the VESTIBULAR NUCLEI of the BRAIN STEM and the median longitudinal fasciculus to the OCULOMOTOR NERVE nuclei. It functions to maintain a stable retinal image during head rotation by generating appropriate compensatory EYE MOVEMENTS. Vestibulo-Ocular Reflex,Reflex, Vestibuloocular,Reflexes, Vestibo-Ocular,Reflexes, Vestibuloocular,Reflex, Vestibulo Ocular,Reflexes, Vestibo Ocular,Vestibo-Ocular Reflexes,Vestibulo Ocular Reflex,Vestibuloocular Reflex,Vestibuloocular Reflexes
D002525 Cerebellar Cortex The superficial GRAY MATTER of the CEREBELLUM. It consists of two main layers, the stratum moleculare and the stratum granulosum. Cortex Cerebelli,Cerebelli, Cortex,Cerebellus, Cortex,Cortex Cerebellus,Cortex, Cerebellar
D005403 Fixation, Ocular Positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye. Focusing, Ocular,Ocular Fixation,Eye Gaze,Eye Gazes,Gaze, Eye,Gazes, Eye,Ocular Focusing
D006257 Head The upper part of the human body, or the front or upper part of the body of an animal, typically separated from the rest of the body by a neck, and containing the brain, mouth, and sense organs. Heads
D000200 Action Potentials Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli. Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012399 Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Clinorotation,Clinorotations,Rotations
D012438 Saccades An abrupt voluntary shift in ocular fixation from one point to another, as occurs in reading. Pursuit, Saccadic,Saccadic Eye Movements,Eye Movement, Saccadic,Eye Movements, Saccadic,Movement, Saccadic Eye,Movements, Saccadic Eye,Pursuits, Saccadic,Saccade,Saccadic Eye Movement,Saccadic Pursuit,Saccadic Pursuits

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