Reciprocity between the cerebellum and the cerebral cortex: Nonlinear dynamics in microscopic modules for generating voluntary motor commands

Abstract

The cerebellum and basal ganglia are reciprocally connected with the cerebral cortex, forming many loops that function as distributed processing modules. Here we present a detailed model of one microscopic loop between the motor cortex and the cerebellum, and we show how small arrays of these microscopic loops (CB modules) can be used to generate biologically plausible motor commands for controlling movement. A fundamental feature of CB modules is the presence of positive feedback loops between the cerebellar nucleus and the motor cortex. We use nonlinear dynamics to model one microscopic loop and to investigate its bistable properties. Simulations demonstrate an ability to program a motor command well in advance of command generation and an ability to vary command duration. However, control of command intensity is minimal, which could interfere with the control of movement velocity. To assess these hypotheses, we use a minimal nonlinear model of the neuromuscular (NM) system that translates motor commands into actual movements. Simulations of the combined CB-NM modular model indicate that movement duration is readily controlled, whereas velocity is poorly controlled. We then explore how an array of eight CB-NM modules can be used to control the direction and endpoint of a planar movement. In actuality, thousands of such microscopic loops function together as an array of adjustable pattern generators for programming and regulating the composite motor commands that control limb movements. We discuss the biological plausibility and limitations of the model. We also discuss ways in which an agent-based representation can take advantage of the modularity in order to model this complex system.

Consensus Paper: Towards a Systems-Level View of Cerebellar Function: the Interplay Between Cerebellum, Basal Ganglia, and Cortex

“…5. Positive feedback through cerebellar nucleus causes the loop to behave in a bistable manner [105]. Bistability is regulated by prominent inhibitory input from the cerebellar cortex (red circles), designating the refinement stage in Fig.…”

The Complexities of Agent-Based Modeling Output Analysis

“…Agent-based models (ABMs) have been gaining popularity across disciplines and have become increasingly sophisticated. The last two decades have seen excellent examples of ABM applications in a broad spectrum of disciplines including ecology (Grimm & Railsback 2005;Thiele & Grimm 2010), economics (Kirman 1992;Tesfatsion & Judd 2006), health care (Effken et al 2012), sociology (Macy & Willer 2002;Squazzoni 2012), geography (Brown & Robinson 2006), anthropology (Axelrod & Hammond 2003), archaeology (Axtell et al 2002), bio-terrorism (Carley et al 2006), business (North & Macal 2007), education (Abrahamson et al 2007), medical research (An & Wilensky 2009), military tactics (Ilachinski 2000), neuroscience (Wang et al 2008), political science (Epstein 2002), urban development and land use (Brown et al 2005), and zoology (Bryson et al 2007). This methodology now also penetrates organizational studies (Carley & Lee 1998;Lee & Carley 2004;Chang & Harrington 2006), governance (Ghorbani et al 2013), and is becoming actively employed in psychology and other behavioural studies, exploiting data from laboratory experiments and surveys (Duffy 2006;Contini et al 2007;Klingert & Meyer 2012).…”

Distributed cerebellar plasticity implements adaptable gain control in a manipulation task: a closed-loop robotic simulation

“…This adaptable gain control requires closed-loop interactions between command centers and effectors and is thought to involve the cerebellum embedded in the so-called forward controller loop (Schweighofer et al, 1998a; Wolpert et al, 1998; Wolpert and Ghahramani, 2000). In fact, the abstraction of models (kinematics and dynamics) of objects under manipulation (Shadmehr and Mussa-Ivaldi, 2012) is efficiently achieved thanks to close interaction between the cerebral and the cerebellar cortex (Middleton and Strick, 2000; Wang et al, 2008). However, two main issues remained unresolved.…”