• Robots

'Direct Pathway' Connections to Globus Pallidus in a Computational Model of the Basal Ganglia

R.Wood, K.Gurney and P.Redgrave

This poster was presented at the BNA2001 Conference in Harrogate, April 8th-11th 2001.

REFERENCE: Wood, R., Gurney, K., and Redgrave, P. (2001) 'Direct pathway' connections to globus pallidus in a computational model of the basal ganglia. British Neuroscience Association Abstracts, 16, p90.

Introduction

Action selection and the basal ganglia

Recently Redgrave Prescott and Gurney (1999) have suggested that the basal ganglia (BG) plays a crucial role in solving the action selection problem in vertebrates. Based on this premise Gurney, Prescott and Redgrave (2001a,b) have proposed a quantitative model of intrinsic BG processing. Presently little is know of the functional architecture of the basal ganglia. The current prevailing model (Albin et al 1989), based on a direct and an indirect pathway, has been shown to have several short comings. First it fails to account for several anatomically important pathways within the BG. Second, it has yet to be developed as a full computational model so that its claims remain to be substantiated. Third it fails to accommodate recent clinical and anatomical data. Given this situation many people believe that the functional architecture of the BG is ready for review (Albin et al, 1995). The new model proposed by Gurney et al (2001a,b) reinterprets BG anatomy as a set of neural mechanisms for selection. It explains quantitatively the selection operations of the BG and describes the role of dopamine (DA) within the context of action selection.

Imposing the computational hypothesis of action selection on the BG anatomy results in a new, dual-pathway functional architecture. A selection pathway proper, which operates through disinhibition of the output nuclei (GPi/SNr), and a control pathway which modulates the selection process in the first pathway via innervation from GPe. In addition, dopaminergic innervation has been incorporated into the model and been shown to affect the 'promiscuity' of selection.

New anatomical data

Gerfen (1992) and more recently Wu et al (2000), have shown that a subgroup of striatal medium spiny neurons project to the entopeduncular nucleus (EP), the globus pallidus (GP) and the substantia nigra pars reticulata (SNr) [3]. As such this suggests a relatively weak pathway between the striatal medium spiny neuron, with predominantly D1 dopamine receptors, and the GPe. The current study aims to incorporate this anatomical data into the selection-control BG model.

This new data represents a challenge for our model and so we sought to discover its implications for the new functional architecture.

Aims

  1. To show that the selection-control pathway model of the functional architecture of the BG can accommodate the new anatomical data described above. That is:
  2. The 'selection' and 'control' pathways retain their functional integrity.
  3. The major features of the selection behaviour of the model remain intact.
  4. To uncover the functional role of the striato-pallidal pathway in the context of action selection.

The Prevailing Direct-Indirect Pathway Model [1]

The New Selection-Control Pathway Model [2]

Type I, II, and III striatal medium spiny neurons

Modelling the New Anatomical Data [3]

Results a: Basic Selection Properties [4]

Results b: The effects of dopamine on selection [5] [6]

Two features of the augmented model which are apparent from the bubble plots:

Conclusion

References


Gerfen (1992); The Neostriatal mosaic: multiple levels of compartmental organisation in the Basal Ganglia, Annual Rev Neuroscience, 15, 123-124.
Gurney, Prescott and Redgrave (2001a); A computational model of action selection in the basal ganglia. I. A new functional anatomy, Biological Cybernetics, (in press).
Gurney, Prescott and Redgrave (2001b); A computational model of action selection in the basal ganglia. II. Analysis and simulation of behaviour, Biological Cybernetics, (in press).
Redgrave, Prescott, and Gurney (1999); The basal ganglia: a vertebrate solution to the selection problem?, Neuroscience, 89, 1009-1023.
Albin, Young and Penney (1989), The functional anatomy of basal ganglia disorders, Trends in Neuroscience, 12, 366-375.
Albin, Young and Penney (1995) The functional anatomy of disorders of the basal ganglia, Trends in Neuroscience, 18, 63-64.
Wu, Richard and Parent, (2000); Neuroscience Research, 83, 46-62.