Effects of STN DBS and auditory cueing on the performance of sequential movements and the occurrence of action tremor in Parkinson's disease.

Background: Parkinson's disease (PD) patients show a higher ability to perform repetitive movements when they are cued by external stimuli, suggesting that rhythmic synchronization with an auditory timekeeper can be achieved in the absence of intact basal ganglia function. Deep brain stimulation (DBS) is another therapeutic method that improves movement performance in PD and may suppress or enhance action tremor. However, the combined effect of these therapies on action tremor has not been studied yet.

Synchrony in Parkinson's disease: importance of intrinsic properties of the external globus pallidus.

The mechanisms for the emergence and transmission of synchronized oscillations in Parkinson's disease, which are potentially causal to motor deficits, remain debated. Aside from the motor cortex and the subthalamic nucleus, the external globus pallidus (GPe) has been shown to be essential for the maintenance of these oscillations and plays a major role in sculpting neural network activity in the basal ganglia (BG). While neural activity of the healthy GPe shows almost no correlations between pairs of neurons, prominent synchronization in the β frequency band arises after dopamine depletion.

Power spectral density analysis of physiological, rest and action tremor in Parkinson's disease patients treated with deep brain stimulation.

Background: Observation of the signals recorded from the extremities of Parkinson's disease patients showing rest and/or action tremor reveal a distinct high power resonance peak in the frequency band corresponding to tremor. The aim of the study was to investigate, using quantitative measures, how clinically effective and less effective deep brain stimulation protocols redistribute movement power over the frequency bands associated with movement, pathological and physiological tremor, and whether normal physiological tremor may reappear during those periods that tremor is absent.

Methods: The power spectral density patterns of rest and action tremor were studied in 7 Parkinson's disease patients treated with (bilateral) deep brain stimulation of the subthalamic nucleus.

Modeling the vagus nerve system with the Unified Modeling Language.

Traditionally, the means of describing anatomical and physiological structures of the autonomic nervous system is natural language, drawings and images as represented in the scientific literature. In behavioral studies of this system, mathematical and electrical models and computer simulation tools are in use. In this article, we propose the use of the Unified Modeling Language to describe and specify the anatomical and physiological structures and indicate how these can be enriched to capture the behavioral view as well.

Phase-dependent effects of stimuli locked to oscillatory activity in cultured cortical networks.

The archetypal activity pattern in cultures of dissociated neurons is spontaneous network-wide bursting. Bursts may interfere with controlled activation of synaptic plasticity, but can be suppressed by the application of stimuli at a sufficient rate. We sinusoidally modulated (4 Hz) the pulse rate of random background stimulation (RBS) and found that cultures were more active, burst less frequently, and expressed oscillatory activity.

The effect of learning on bursting.

We have studied the effect that learning a new stimulus-response (SR) relationship had within a neuronal network cultured on a multielectrode array. For training, we applied repetitive focal electrical stimulation delivered at a low rate (<1/s). Stimulation was withdrawn when a desired SR success ratio was achieved.

Single pulse and pulse train modulation of cutaneous electrical stimulation: a comparison of methods.

: Changing the amplitude of single rectangular pulse stimuli (SP) has the disadvantage of recruiting tactile and nociceptive fibers in a changing, unknown proportion. Keeping the amplitude constant, but applying a varying number of pulses in a train is another way of stimulus variation, keeping the proportion constant. So, pulse trains (PT) with a variable number of pulses but fixed amplitude might be more suitable to study nonperipheral aspects of processing of stimuli.

The subthalamic nucleus part II: modelling and simulation of activity.

Part I of The Subthalamic Nucleus (volume 198) (STN) accentuates the gap between experimental animal and human information concerning subthalamic development, cytology, topography and connections.The light and electron microscopical cytology focuses on the open nucleus concept and the neuronal types present in the STN. The cytochemistry encompasses enzymes, NO, glial fibrillary acidic protein (GFAP), calcium binding proteins, and receptors (dopamine, cannabinoid, opioid, glutamate, gamma-aminobutyric acid (GABA), serotonin, cholinergic, and calcium channels).

The subthalamic nucleus. Part I: development, cytology, topography and connections.

This monograph (Part I of two volumes) on the subthalamic nucleus (STN) accentuates the gap between experimental animal and human information concerning subthalamic development, cytology, topography and connections. The light and electron microscopical cytology focuses on the open nucleus concept and the neuronal types present in the STN. The cytochemistry encompasses enzymes, NO, glial fibrillary acidic protein (GFAP), calcium binding proteins, and receptors (dopamine, cannabinoid, opioid, glutamate, gamma-aminobutyric acid (GABA), serotonin, cholinergic, and calcium channels).

Analysis of cultured neuronal networks using intraburst firing characteristics.

It is an open question whether neuronal networks, cultured on multielectrode arrays, retain any capability to usefully process information (learning and memory). A necessary prerequisite for learning is that stimulation can induce lasting changes in the network. To observe these changes, one needs a method to describe the network in sufficient detail, while stable in normal circumstances.

Spatial clustering analysis in neuroanatomy: applications of different approaches to motor nerve fiber distribution.

Spatial organization of the nerve fibers in the peripheral nerves may be important for the studies of axonal regeneration, the degenerative nerve diseases and the construction of interfaces with peripheral nerves, such as nerve prostheses. Functional topography of motor axons related to the gastrocnemius muscle was revealed in the ventral spinal roots by retrograde tracing. Gastrocnemius muscles of adult rats were injected with the tracer Fluoro-Gold.

Automatic morphometry of synaptic boutons of cultured cells using granulometric analysis of digital images.

Numbers, linear density, and surface area of synaptic boutons can be important parameters in studies on synaptic plasticity in cultured neurons. We present a method for automatic identification and morphometry of boutons based on filtering of digital images using granulometric analysis. Cultures of cortical neurons (DIV8 and DIV21) were fixed and marked with fluorescently labeled antibodies for synapsin I (a marker for synaptic boutons) and MAP-2 (a marker for dendrites).

Three-dimensional topography of the motor endplates of the rat gastrocnemius muscle.

Spatial distribution of motor endplates affects the shape of the electrical activity recorded from muscle. In order to provide information for realistic models of action potential propagation within muscles, we assembled three-dimensional maps of the motor endplates of the rat medial gastrocnemius (MGM) and lateral gastrocnemius (MGL) muscles. The maps were assembled from histological cross sections stained for acetylcholinesterase activity.

Adhesion and proliferation of human Schwann cells on adhesive coatings.

Attachment to and proliferation on the substrate are deemed important considerations when Schwann cells (SCs) are to be seeded in synthetic nerve grafts. Attachment is a prerequisite for the SCs to survive and fast proliferation will yield large numbers of SCs in a short time, which appears promising for stimulation of peripheral nerve regeneration. The aim of the present study was to compare the adhesion and proliferation of human Schwann cells (HSCs) on different substrates.

Adhesion and growth of human Schwann cells on trimethylene carbonate (co)polymers.

Seeding of artificial nerve grafts with Schwann cells is a promising strategy for bridging large nerve defects. The aim of the present study was to evaluate the adhesion and growth of human Schwann cells (HSCs) on 1,3-trimethylene carbonate (TMC) and epsilon-caprolactone copolymers, with the final goal of using these materials in the development of an artificial nerve graft. The adhesion, proliferation, and morphology of HSCs on copolymers containing 10 and 82 mol % of TMC and on the parent homopolymers were investigated.

Geometry-based finite-element modeling of the electrical contact between a cultured neuron and a microelectrode.

The electrical contact between a substrate embedded microelectrode and a cultured neuron depends on the geometry of the neuron-electrode interface. Interpretation and improvement of these contacts requires proper modeling of all coupling mechanisms. In literature, it is common practice to model the neuron-electrode contact using lumped circuits in which large simplifications are made in the representation of the interface geometry.

Repair of ventral root avulsion using autologous nerve grafts in cats.

This study focuses on the capacity of motor axons to elongate from the spinal cord through an autologous nerve graft into a spinal nerve. Applying a ventral surgical approach, C7 ventral roots were avulsed from the cord in 12 cats. Autologous saphenous nerve grafts were implanted into the cord at the ventral root outlet site and coaptated to the spinal nerve.

Anatomy of the arcus tendineus fasciae pelvis in females.

Because of its proximity to the urethra, the anterior part of the arcus tendineus fasciae pelvis (ATFP) may be used in urethrosuspension procedures for urinary stress incontinence. In this study, 10 embalmed female cadaver hemipelves were dissected and their gross anatomy described. In females, the ATFP is a condensation of the endopelvic fascia.

Extracellular stimulation window explained by a geometry-based model of the neuron-electrode contact.

Extracellular stimulation of single cultured neurons which are completely sealing a microelectrode is usually performed using anodic or biphasic currents of at least 200 nA. However, recently obtained experimental data demonstrate the possibility to stimulate a neuron using cathodic current pulses with less amplitude. Also, a stimulation window is observed.

Modeled channel distributions explain extracellular recordings from cultured neurons sealed to microelectrodes.

Amplitudes and shapes of extracellular recordings from single neurons cultured on a substrate embedded microelectrode depend not only on the volume conducting properties of the neuron-electrode interface, but might also depend on the distribution of voltage-sensitive channels over the neuronal membrane. In this paper, finite-element modeling is used to quantify the effect of these channel distributions on the neuron-electrode contact. Slight accumulation or depletion of voltage-sensitive channels in the sealing membrane of the neuron results in various shapes and amplitudes of simulated extracellular recordings.

Repair of ventral root avulsions of the brachial plexus: a review.

Traumatic root avulsions of the brachial plexus constitute a devastating lesion resulting in loss of function of the upper limb and carry a large emotional and socioeconomic impact. In this literature survey, the different factors involved in root avulsion are discussed in combination with various surgical techniques for repair of experimental ventral root avulsion. Until now repair of root avulsions did not generate unequivocal proof of recovery of limb function, particularly of the hand.

Investigating membrane breakdown of neuronal cells exposed to nonuniform electric fields by finite-element modeling and experiments.

High electric field strengths may induce high cell membrane potentials. At a certain breakdown level the membrane potential becomes constant due to the transition from an insulating state into a high conductivity and high permeability state. Pores are thought to be created through which molecules may be transported into and out of the cell interior.