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Dopamine depletion in cortical-basal ganglia circuits in Parkinson's disease (PD) grossly disturbs movement and cognition. Classic models relate Parkinsonian dysfunction to changes in firing rates of basal ganglia neurons. However, disturbances in other dynamics of neural activity are also common. Taking both inappropriate firing rates and other dynamics into account and determining how changes in the properties of these neural circuits that occur during PD impact on information coding are thus imperative. Here, we examined in vivo network dynamics in the external globus pallidus (GPe) of rats before and after chronic dopamine depletion. Dopamine depletion led to decreases in the firing rates of GPe neurons and increases in synchronized network oscillations in the beta frequency (13-30 Hz) band. Using logistic regression models, we determined the combined and separate impacts of these factors on network entropy, a measure of the upper bound of information coding capacity. Importantly, changes in these features in dopamine-depleted rats led to a significant decrease in GPe network entropy. Changes in firing rates had the largest impact on entropy, with changes in synchrony also decreasing entropy at the network level. Changes in autocorrelations tended to offset these effects because autocorrelations decreased entropy more in the control animals. Thus it is possible that reduced information coding capacity within basal ganglia networks may contribute to the behavioral deficits accompanying PD.

Original publication

DOI

10.1152/jn.00344.2009

Type

Journal article

Journal

J Neurophysiol

Publication Date

08/2009

Volume

102

Pages

1092 - 1102

Keywords

Action Potentials, Adrenergic Agents, Analysis of Variance, Animals, Dopamine, Globus Pallidus, Logistic Models, Male, Microelectrodes, Models, Neurological, Neurons, Oxidopamine, Parkinsonian Disorders, Periodicity, Rats, Rats, Sprague-Dawley, Substantia Nigra, Time Factors