Abstract-Ambulatory monitoring of motor symptoms in Parkinson's disease (PD) can improve our therapeutic strategies, especially in patients with motor fluctuations. Previously published monitors usually assess only one or a few basic aspects of the cardinal motor symptoms in a laboratory setting. We developed a novel ambulatory monitoring system that provides a complete motor assessment by simultaneously analyzing current motor activity of the patient (e.g., sitting, walking, etc.) and the severity of many aspects related to tremor, bradykinesia, and hypokinesia. The monitor consists of a set of four inertial sensors. Validity of our monitor was established in seven healthy controls and six PD patients treated with deep brain stimulation (DBS) of the subthalamic nucleus. The patients were tested at three different levels of DBS treatment. Subjects were monitored while performing different tasks, including motor tests of the Unified PD Rating Scale (UPDRS). Output of the monitor was compared to simultaneously recorded videos. The monitor proved very accurate in discriminating between several motor activities. Monitor output correlated well with blinded UPDRS ratings during different DBS levels. The combined analysis of motor activity and symptom severity by our PD monitor brings true ambulatory monitoring of a wide variety of motor symptoms one step closer.

Chronic motor cortex stimulation (MCS) is currently being investigated as a treatment method for Parkinson's disease (PD). Unfortunately, the underlying mechanisms of this treatment are unclear and there are many uncertainties regarding the most effective stimulation parameters and electrode configuration. In this paper, we present a MCS model with a 3D representation of several axonal populations. The model predicts that the activation of either the basket cell or pyramidal tract (PT) type axons is involved in the clinical effect of MCS. We propose stimulation protocols selectively targeting one of these two axon types. To selectively target the basket cell axons, our simulations suggest using either cathodal or bipolar stimulation with the electrode strip placed perpendicular rather than parallel to the gyrus. Furthermore, selectivity can be increased by using multiple cathodes. PT type axons can be selectively targeted with anodal stimulation using electrodes with large contact sizes. Placing the electrode epidurally is advisable over subdural placement. These selective protocols, when practically implemented, can be used to further test which axon type should be activated for clinically effective MCS and can subsequently be applied to optimize treatment. In conclusion, this paper increases insight into the neuronal population involved in the clinical effect of MCS on PD and proposes strategies to improve this therapy.

The subthalamic nucleus (STN) receives monosynaptic glutamatergic afferents from different areas of the cortex, known as the "hyperdirect" pathway. The STN has been divided into three distinct subdivisions, motor, limbic, and associative parts in line with the concept of parallel information processing. The extent to which the parallel information processing coming from distinct cortical areas overlaps in the different territories of the STN is still a matter of debate and the proposed role of dopaminergic neurons in maintaining the coherence of responses to cortical inputs in each territory is not documented. Using extracellular electrophysiological approaches, we investigated to what degree the motor and non-motor regions in the STN are segregated in control and dopamine (DA) depleted rats. We performed electrical stimulation of different cortical areas and recorded STN neuronal responses. We showed that motor and non-motor cortico-subthalamic pathways are not fully segregated, but partially integrated in the rat. This integration was mostly present through the indirect pathway. The spatial distribution and response latencies were the same in sham and 6-hydroxydopamine lesioned animals. The inhibitory phase was, however, less apparent in the lesioned animals. In conclusion, this study provides the first evidence that motor and non-motor cortico-subthalamic pathways in the rat are not fully segregated, but partially integrated. This integration was mostly present through the indirect pathway. We also show that the inhibitory phase induced by GABAergic inputs from the external segment of the globus pallidus is reduced in the DA-depleted animals.

To prevent seizures the current density should be lowered, so that motor cortex stimulation-evoked responses can be safely used during deep brain stimulation surgery.

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