The Basal Ganglia
The basal ganglia (BG) are known to play a role in motor, cognitive and associative functions (see Sect. 1 of Part I of The Subthalamic Nucleus). However, the role of the BG in motor control appears to be the dominant one, and will be the emphasis of this
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1 Introduction In order to investigate the dynamics of single subthalamic nucleus (STN) neurons and the activity patterns when STN neurons are connected with other types of (basal ganglia) neurons, in vitro brain slices and networks of dissociated neurons of a specific type cultured on a multi-electrode array (MEA) may be used to identify the ion channels that determine membrane dynamics and to investigate network activity in open-loop configurations. In addition, mathematical modelling provides a powerful tool to test neuron and network behaviour under different conditions. Especially the emergence of deep brain stimulation (DBS) as an effective treatment for the symptoms of Parkinson's disease (PD) has recently motivated the development of several computational models to probe (part of) the underlying network activity as well as the mechanisms of stimulus-induced suppression of PD-induced activity patterns. Single-compartment, conductance-based models may be developed on the basis of patch clamp studies in which all types of ion channels within the membrane and their dynamics are retrieved. Networks consisting of a large number of different types of neurons and different types of inter-connections may be created using low-dimensional models based on these empirical models. The network of the basal ganglia and the role of the STN within this network is described in Sect. 2 (this volume). Since a large number of experimental as well as modelling studies focus on PD, changes in network activity under dopaminedepleted conditions are described. An overview of in vitro experiments is given in Sect. 3 and 4 (this volume) in which the different modes of activity of STN cells that were observed are summarized. In Sect. 5, various current STN neuron and network models are summarized in view of the occurrence of bursting activity and synchronization within the network of the basal ganglia, as occurs in PD, and the use of STN-DBS (deep brain stimulation), which is currently the most frequently used and most effective clinical method for the reduction of the symptoms of PD. In Sect. 6 a comparison of Part I and Part II of The Subthalamic Nucleus is given.
2 The Basal Ganglia The basal ganglia (BG) are known to play a role in motor, cognitive and associative functions (see Sect. 1 of Part I of The Subthalamic Nucleus). However, the role of the BG in motor control appears to be the dominant one, and will be the emphasis of this research. It is widely accepted that the BG play a crucial role in the control of voluntary movement. However, what exactly the BG do for voluntary movement is still under debate. Many clues as to the function of this complex group of subcortical structures have been obtained by examining the deficits that occur following disorders of the BG such as PD and Huntington's disease. Animal models of MPTP-induced parkinsonism have played a crucial role in investigations. Singlecell microelectrode recordings of neuronal activity, as well as imaging studies of
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The Basal Ganglia
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