Short term plasticity within the basal ganglia - a systems level computational investigation
© Lindahl and Kotaleski; licensee BioMed Central Ltd. 2011
Published: 18 July 2011
Striatal direct pathway medium spiny neurons (MSNs) converge, with inhibitory synapses onto output nuclei substantia nigra reticulata (SNr), which keep neurons in the thalamus, superior colliculus and pendunculopontine nuclei under tonic inhibition . Recent experimental findings  have found short term facilitation in MSN synapses onto SNr neurons. We investigate the functional consequences of these findings using a basal ganglia system level model, with spiking MSNs modeled according to Izhikevich’s simple model  and with facilitating synapses  fitted to data in . The model is implemented in the NEST  simulator. We quantify how striatal populations of MSNs can control activity in SNr neurons, and to what extent this depends on having weak static, strong static and facilitating synapses between MSNs and SNr neurons.
Our simulation experiments predict that facilitating synapses allow baseline firing of presynaptic MSNs without suppressing target SNr neurons, while burst activation of only a few of these presynaptic striatal neurons can suppress the activity of one SNr neuron. This is in accordance with extracellular recordings in awake animals , where task dependent activity is transferred from a broad striatal population to a smaller subpopulation, responding increasingly stronger during learning of a task dependent behavior.
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