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Behavioral/Systems/Cognitive A Reevaluation of the Inverse Dynamic Model for
 

Summary: Behavioral/Systems/Cognitive
A Reevaluation of the Inverse Dynamic Model for
Eye Movements
Andrea M. Green,1 Hui Meng,2 and Dora E. Angelaki2
1DeŽpartement de Physiologie, UniversiteŽ de MontreŽal, MontreŽal, QueŽbec, Canada H3T 1J4, and 2Department of Anatomy and Neurobiology, Washington
University School of Medicine, St. Louis, Missouri 63110
To construct an appropriate motor command from signals that provide a representation of desired action, the nervous system must take
into account the dynamic characteristics of the motor plant to be controlled. In the oculomotor system, signals specifying desired eye
velocity are thought to be transformed into motor commands by an inverse dynamic model of the eye plant that is shared for all types of
eye movements and implemented by a weighted combination of eye velocity and position signals. Neurons in the prepositus hypoglossi
andadjacentmedialvestibularnuclei(PH-BTneurons)weretraditionallythoughttoencodethe"eyeposition"componentofthisinverse
model. However, not only are PH-BT responses inconsistent with this theoretical role, but compensatory eye movement responses to
translation do not show evidence for processing by a common inverse dynamic model. Prompted by these discrepancies between
theoretical notions and experimental observations, we reevaluated these concepts using multiple-frequency rotational and translational
headmovements.Compatiblewiththenotionofacommoninversemodel,weshowthatPH-BTresponsesareuniqueamongallpremotor
cell types in bearing a consistent relationship to the motor output during eye movements driven by different sensory stimuli. However,
because their responses are dynamically identical to those of motoneurons, PH-BT neurons do not simply represent an internal compo-
nent of the inverse model, but rather its output. They encode and distribute an estimate of the motor command, a signal critical for
accurate motor execution and learning.
Key words: internal model; eye movement; vestibular; efference copy; sensorimotor; motor control

  

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

 

Collections: Biology and Medicine