title: Deep cerebellar neurons mirror the spinal cord's gain to implement an inverse controller.
abstract: Smooth and coordinated motion requires precisely timed muscle activation patterns, which due to biophysical limitations, must be predictive and executed in a feed-forward manner. In a previous study, we tested Kawato's original proposition, that the cerebellum implements an inverse controller, by mapping a multizonal microcomplex's (MZMC) biophysics to a joint's inverse transfer function and showing that inferior olivary neuron may use their intrinsic oscillations to mirror a joint's oscillatory dynamics. Here, to continue to validate our mapping, we propose that climbing fiber input into the deep cerebellar nucleus (DCN) triggers rebounds, primed by Purkinje cell inhibition, implementing gain on IO's signal to mirror the spinal cord reflex's gain thereby achieving inverse control. We used biophysical modeling to show that Purkinje cell inhibition and climbing fiber excitation interact in a multiplicative fashion to set DCN's rebound strength; where the former primes the cell for rebound by deinactivating its T-type Ca2(+) channels and the latter triggers the channels by rapidly depolarizing the cell. We combined this result with our control theory mapping to predict how experimentally injecting current into DCN will affect overall motor output performance, and found that injecting current will proportionally scale the output and unmask the joint's natural response as observed by motor output ringing at the joint's natural frequency. Experimental verification of this prediction will lend support to a MZMC as a joint's inverse controller and the role we assigned underlying biophysical principles that enable it.
authors.affiliation: Department of Bioengineering, Stanford University, USA. rodrigoa@stanford.edu
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Alvarez-Icaza
authors.forename: Kwabena
authors.initials: K
authors.lastname: Boahen
mesh_terms: D000200:Action Potentials / Q000502:physiology; D002529:Cerebellar Nuclei / Q000166:cytology* / Q000502:physiology; D002531:Cerebellum / Q000033:anatomy & histology / Q000502:physiology; D008954:Models, Biological; D009068:Movement / Q000502:physiology; D011689:Purkinje Cells / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*