Abstract
the motor system may use intemal predictive models of the motor apparatus
to achieve better control than would be possible by negative feedback.
Several theories have proposed that the cerebellum may form these
predictive representations, In this article, we review these theories
and try to unify them by reference to an engineering control model
known as a Smith Pre dictor. We suggest that the cerebellum forms
two types of internal model. One model is a forward predictive model
of the motor apparatus (e.g. , limb and muscle), providing a rapid
prediction of the sensory consequences of each movement. The second
model is of the time delays in the control loop (due to receptor
and effector delays, axona conductances, and cognitive processing
delays). This model delays a copy of the rapid prediction so that
it can be compared in temporal register with actual sensory feedback
from the movement. The result of this comparison is used both to
correct for errors in perf.ormance and as a training signal to learn
the first model We discuss evidence that the cerebellum could form
both of these models and suggest that the cerebellum may hold at
least two separate Smith Predictors. One, in the lateral cerebellum,
would predict the movement outcome in visual, egocentric, or peripersonaJ
coordinates. Another, in the intermediate cerebellum, would predict
the consequences in motor coordinates. Generalization of the Smith
Predictor theory is discussed in ight of cerebellar involvement
in nonmotor control systems, including autonomic functions and cognition
Users
Please
log in to take part in the discussion (add own reviews or comments).