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Brief Communications Neural Correlates of Forward and Inverse Models for Eye
 

Summary: Brief Communications
Neural Correlates of Forward and Inverse Models for Eye
Movements: Evidence from Three-Dimensional Kinematics
Fatema F. Ghasia, Hui Meng, and Dora E. Angelaki
Department of Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110
Inverse and forward dynamic models have been conceptually important in computational motor control. In particular, inverse models
are thought to convert desired action into appropriate motor commands. In parallel, forward models predict the consequences of the
motor command on behavior by constructing an efference copy of the actual movement. Despite theoretical appeal, their neural repre-
sentation has remained elusive. Here, we provide evidence supporting the notion that a group of premotor neurons called burst-tonic
(BT) cells represent the output of the inverse model for eye movements. We show that BT neurons, like extraocular motoneurons but
different from the evoked eye movement, do not carry signals appropriate for the half-angle rule of ocular kinematics during smooth-
pursuit eye movements from eccentric positions. Along with findings of identical response dynamics as motoneurons, these results
strongly suggest that BT cells carry a replica of the motor command. In contrast, eye-head (EH) neurons, a premotor cell type that is the
target of Purkinje cell inhibition from the cerebellar flocculus/ventral paraflocculus, exhibit properties that could be consistent with the
half-anglerule.Therefore,EHcellsmaybefunctionallyrelatedtotheoutputofaforwardinternalmodelthoughttoconstructanefference
copy of the actual eye movement.
Key words: torsion; Listing's law; half-angle rule; burst-tonic cells; internal model; smooth pursuit
Introduction
A contemporary concept in motor control is that desired action is
transformed into an appropriate motor command through an

  

Source: Angelaki, Dora - Department of Anatomy and Neurobiology, Washington University in St. Louis

 

Collections: Biology and Medicine