[From MK (2014.12.23.1000 CET)]
Advances in Neuroscience
Volume 2014 (2014), Article ID 768313
http://dx.doi.org/10.1155/2014/768313
How Basal Ganglia Outputs Generate Behavior
Henry H. Yin
"The basal ganglia (BG) are a collection of subcortical nuclei
critical for voluntary behavior. According to the standard model, the
output projections from the BG tonically inhibit downstream motor
centers and prevent behavior. A pause in the BG output opens the gate
for behavior, allowing the initiation of actions. Hypokinetic
neurological symptoms, such as inability to initiate actions in
Parkinson’s disease, are explained by excessively high firing rates of
the BG output neurons. This model, widely taught in textbooks, is
contradicted by recent electrophysiological results, which are
reviewed here. In addition, I also introduce a new model, based on the
insight that behavior is a product of closed loop negative feedback
control using internal reference signals rather than sensorimotor
transformations. The nervous system is shown to be a functional
hierarchy comprising independent controllers occupying different
levels, each level controlling specific variables derived from its
perceptual inputs. The BG represent the level of transition control in
this hierarchy, sending reference signals specifying the succession of
body orientations and configurations. This new model not only explains
the major symptoms in movement disorders but also generates a number
of testable predictions."
[...]
"I shall first discuss current models of the BG and recent results
that begin to challenge these models. I shall then explain how control
theory, correctly applied, can help us understand behavior, and how
different control systems can be arranged in a hierarchy using the
principle of cascade control. Finally, I shall discuss the neural
implementation of cascade control and the distinct contributions of
the BG in this functional hierarchy."
Full-text, HTML: http://www.hindawi.com/journals/aneu/2014/768313/
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