Irregular vs. Synchronized activity in Basal Ganglia Circuits

Abstract

Event Abstract Back to Event Irregular vs. Synchronized activity in Basal Ganglia Circuits The basal ganglia (BG) are a group of interconnected subcortical nuclei which are, among other things, involved in neural control of movement. They become impaired in Parkinson’s disease (PD), characterized by akinetic behavior. Recent studies indicate that patterns of oscillatory synchronous activity in BG are strongly relevant to BG physiology and BG disorders. In particular, neuronal activity in the beta-band significantly contributes to akinetic symptoms. The dynamics of these oscillations, their mechanisms and potential functional significance are the subjects of this study. Experimental data: we record neuronal activity during microelectrode-guided target localization in the PD patients undergoing surgery for implantation of DBS electrodes. Extracellular spiking activity and LFPs are recorded simultaneously. Modeling: we also use conductance-based models of subthalamic and pallidal cells to model rhythmic activity in subthalamo-pallidal circuits of BG. Model LFPs are constructed from model neuron’s activity. Data analysis: after appropriate filtering, Hilbert phase is constructed for both signals. Short running window analysis (with surrogates to determine statistical significance) is used to characterize temporal patterns of synchrony in experiment and model. First return maps for the phases are also used to characterize synchronization and compare model with experiment. The results of the analysis indicate that the dynamics of beta-band oscillations in BG is marked by intermittency of synchronized episodes. Oscillations tend to be desynchronized for relatively short time, although the desynchronizing events are quite frequent. The model has large areas in the parameter space, where it generates either irregular and uncorrelated firing patterns or rhythmic correlated activities. There is also an area of intermittent synchrony and, importantly, the first return maps for the phases from model and experiment are very similar in that area. Thus the model’s phase space is organized similarly to those of experimental system during rest in PD. The domain of the existence of intermittent dynamics is in between incoherent regime and synchronized regime, in the area which is characterized by the presence of different types of dynamics. Simulation of noisy version of our model confirmed the robustness of the observed dynamics (and thus its relevance to experiment). These observations suggest that in a pathological state, BG networks operate in a regime, which is quite close (in a parameter space) to an irregular activity. Although we do not have microelectrode recordings form normal humans, vast body of other experiments with animal models and humans suggest that healthy state is characterized by the absence of beta-band oscillations at rest. BG still needs them for movement preparation. The organization of the parameter space of the model and similarity of the model and experimental phase space indicate that in a disease (Parkinsonism), BG circuits are relatively close to the presumably healthy uncorrelated state and suggest that this healthy state is very close to the birth of oscillations. This closeness of the irregular healthy state to the pathological regular synchronized state may be justified by the efficiency of producing synchronized oscillations for movement generation. Dopaminergic degeneration in PD shifts the system into a pathological synchronized activity. Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: (2009). Irregular vs. Synchronized activity in Basal Ganglia Circuits. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.228 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 03 Feb 2009; Published Online: 03 Feb 2009. 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