A biophysical model of neuronal dendrites' integrative properties: relations to morphological data

We used a biophysical model to probe the basic integrative properties of primate pallidal neurons in order to obtain a better understanding of Basal Ganglia physiology. The first results we present here deal mainly with the way dendritic morphology influences these properties. Neuronal morphology has been quantitatatively analyzed in 3D. Single fast excitatory synaptic inputs resulting in AMPA receptors activations have been simulated, without regenerative voltage dependent conductances. Dendrites of both pallidal segments (GPi and GPe) showed a strong dependence of the synaptic efficacy upon distance from soma, but even the most distal dendritic synaptic sites were able to substantially depolarize the cell body. The mean synaptic efficacy was the same in both populations, but the attenuation of propagated post-synaptic potentials was higher in GPi neurons. All these features were very dependent on the dendritic diameters which appear to constitute a key parameter in these neuronal populations both with respect to the integration of afferent information and to the differences between cells in performing this task.