Basal ganglia-thalamocortical loop model of action selection (Humphries and Gurney 2002)

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We embed our basal ganglia model into a wider circuit containing the motor thalamocortical loop and thalamic reticular nucleus (TRN). Simulation of this extended model showed that the additions gave five main results which are desirable in a selection/switching mechanism. First, low salience actions (i.e. those with low urgency) could be selected. Second, the range of salience values over which actions could be switched between was increased. Third, the contrast between the selected and non-selected actions was enhanced via improved differentiation of outputs from the BG. Fourth, transient increases in the salience of a non-selected action were prevented from interrupting the ongoing action, unless the transient was of sufficient magnitude. Finally, the selection of the ongoing action persisted when a new closely matched salience action became active. The first result was facilitated by the thalamocortical loop; the rest were dependent on the presence of the TRN. Thus, we conclude that the results are consistent with these structures having clearly defined functions in action selection.
1 . Humphries MD (2003) High level modeling of dopamine mechanisms in striatal neurons Technical Report ABRG 3
2 . Humphries MD, Gurney KN (2002) The role of intra-thalamic and thalamocortical circuits in action selection. Network 13:131-56 [PubMed]
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Model Information (Click on a link to find other models with that property)
Model Type: Connectionist Network;
Brain Region(s)/Organism:
Cell Type(s):
Gap Junctions:
Transmitter(s): Dopamine;
Simulation Environment: MATLAB; Simulink;
Model Concept(s): Parkinson's; Action Selection/Decision Making;
Implementer(s): Humphries, Mark D [m.d.humphries at];
Search NeuronDB for information about:  Dopamine;
MATLAB version of the extended basal ganglia model


(1) extended_model_ZOH.m is a MATLAB script that replicates the Simulink version

(2) HG_engine.m	is a MATLAB function that encapsulates multiple versions of the model: read its Help comments for full details.
(3) ramp_output.m and DA_ramp_output.m are two different forms of the piece-wise linear output function. The latter is a modified form given in (Humphries, 2003) that captures the effects of dopamine on striatal neuron output. 

Humphries, M. D. & Gurney, K. N. (2002). The role of intra-thalamic and thalamocortical circuits in action selection. Network: Computation in Neural Systems, 13, 131-156.

Humphries, M.D. (2003). High level modeling of dopamine mechanisms in striatal neurons. Technical Report ABRG 3. Dept. Psychology University of Sheffield, UK.