University of Twente Publications
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.
Type = Article
Mostrando recursos 1 - 20 de 20.185
Cortically evoked potentials in the human subthalamic nucleus - Zwartjes, D.G.M.; Janssen, M.L.F.; Heida, T.; Van Kranen-Mastenbroek, V.; Bour, L.; Temel, Y.; Visser-Vandewalle, V.; Martens, H.C.F.; Veltink, P.H.
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) alleviates motor symptoms in Parkinson’s disease (PD) patients. However, in a substantial number of patients the beneficial effects of STN DBS are overshadowed by psychiatric side effects. We hypothesize that stimulation of the STN motor area will provide the optimal effect on the motor symptoms without inducing these side effects, and expect that motor cortex stimulation (MCS) evokes a spatially specific response within the STN, which identifies the STN motor area. We previously showed that MCS evokes responses in the unit activity specifically within certain areas of the STN. Unit activity...
Sentinel Node Biopsy Using a Magnetic Tracer Versus Standard Technique: The SentiMAG Multicentre Trial - Douek, M.; Klaase, Joost M.; Monypenny, I.; Kothari, A.; Zechmeister, K.; Brown, D.; Wyld, L.; Drew, P.; Garmo, H.; Agbaje, O.; Pankhurst, Q.A.; Anninga, B.; Grootendorst, M.; Haken, B. ten; Hall-Craggs, M.; Purushotham, A.; Pinder, S.
The SentiMAG Multicentre Trial evaluated a new magnetic technique for sentinel lymph node biopsy (SLNB) against the standard (radioisotope and blue dye or radioisotope alone). The magnetic technique does not use radiation and provides both a color change (brown dye) and a handheld probe for node localization. The primary end point of this trial was defined as the proportion of sentinel nodes detected with each technique (identification rate).
A total of 160 women with breast cancer scheduled for SLNB, who were clinically and radiologically node negative, were recruited from seven centers in the United Kingdom and The Netherlands. SLNB was...
Magnetic sentinel lymph node biopsy and localization properties of a magnetic tracer in an in vivo porcine model - Anninga, B.; Ahmed, M.; Hemelrijck, M. Van; Pouw, J.J.; Westbroek, D.; Haken, B. ten; Pankhurst, Q.A.
The standard for the treatment of early non-palpable breast cancers is wide local excision directed by wire-guided localization and sentinel lymph node biopsy (SLNB). This has drawbacks technically and due to reliance upon radioisotopes. We evaluated the use of a magnetic tracer for its localization capabilities and concurrent performance of SLNB using a handheld magnetometer in a porcine model as a novel alternative to the current standard. Ethical approval by the IRCAD Ethics Review Board, Strasbourg (France) was received. A magnetic tracer was injected in varying volumes (0.1-5 mL) subcutaneously into the areolar of the left and right 3rd inguinal...
Students' development in self-regulated learning in postgraduate professional education: a longitudinal study - Endedijk, Maaike D.; Vermunt, Jan D.; Meijer, Paulien C.; Brekelmans, Mieke
One of the tasks of postgraduate education is to develop students' conceptions and skills necessary for lifelong learning in their profession. Therefore, this study aimed at identifying students' development in self-regulated learning throughout a postgraduate teacher education programme. A longitudinal design with three measurement occasions was adopted. Student teachers' learning orientations were measured with a questionnaire and their regulation activities by means of multiple structured question logs. Longitudinal multilevel analyses showed that student teachers became more passive in their regulation throughout the programme. Furthermore, only one third of the student teachers changed in the direction of independent meaning-oriented learning. This...
Hepatic resection for metastatic melanoma in The Netherlands: survival and prognostic factors - Ridder, J. de; Walsum, M. van; Nagtegaal, I.D.; Wilt, J. de; Ruers, T.J.M.
Patients with hepatic metastases of melanoma have a very poor prognosis, with a median overall survival of less than 6 months. There are several small heterogeneous studies that have shown an association with prolonged survival in those patients treated with hepatic resection, but the role of surgery remains unclear. We evaluated the safety and efficacy of hepatic resection in a population-based study in the Netherlands for patients with metastatic melanoma and assessed the factors that could affect disease-free and overall survival. Patients with hepatic melanoma metastases who underwent potentially curative resection were identified between 1994 until 2010 using the PALGA...
Individual differences in student teachers' self-regulated learning: An examination of regulation configurations in relation to conceptions of learning to teach - Endedijk, Maaike D.; Brekelmans, Mieke; Verloop, Nico; Sleegers, Peter J.C.; Vermunt, Jan D.
This study aimed at describing the individual differences in student teachers' self-regulated learning to teach in postgraduate professional teacher education programmes. Cross-sectional data were collected from 28 student teachers about their regulation activities and conceptions of learning to teach through open question logs from multiple learning experiences and interviews. The findings showed that the self-regulation activities of student teachers could be represented by five different configurations. In addition, it appeared that student teachers' regulation relate differently to their conceptions of learning then expected from the literature. The implications of these findings are discussed for a better understanding of the role...
Critically reflective dialogues in learning communities of professionals - Groot, Esther de; Endedijk, Maaike D.; Jaarsma, A. Debbie C.; Simons, P. Robert-Jan; Beukelen, Peter van
Communities in which professionals share and create knowledge potentially support their continued learning. To realise this potential more fully, members are required to reflect critically. For learning at work such behaviour has been described as critically reflective work behaviour, consisting of six aspects: challenging groupthink, critical opinion sharing, an openness about mistakes, asking for and giving feedback, experimentation and research utilisation. We studied whether and how these aspects can be distinguished in dialogues of seven different communities of veterinary professionals (critically reflective dialogues). Our exploration of the nature of critically reflective dialogues resulted in an analytical framework. Within each aspect...
Quantitative analysis of superparamagnetic contrast agent in sentinel lymph nodes using ex vivo vibrating sample magnetometry - Visscher, M.; Pouw, J.J.; Baarlen, J. van; Klaase, J.M.; Haken, B. ten
As the first step in developing a new clinical technique for the magnetic detection of colorectal sentinel lymph nodes (SLNs), a method is developed to measure the magnetic content in intact, formalin fixated lymph nodes using a vibrating sample magnetometer (VSM). A suspension of superparamagnetic nanoparticles is injected ex vivo around the tumor in the resected colon segments. A selection of three lymph nodes is excised from the region around the tumor and is separately measured in the VSM. The iron content in the lymph nodes is quantified from the magnetic moment curve using the Langevin model for superparamagnetism and...
Diffusing substances during spreading depolarization: Analytical expressions for propagation speed, triggering, and concentration time courses - Zandt, B.; Haken, B. ten; Putten, M.J.A.M. van
Spreading depolarization (SD) is an important phenomenon in stroke and migraine. However, the processes underlying the propagation of SD are still poorly understood, and an elementary model that is both physiological and quantitative is lacking. We show that, during the onset and propagation of SD, the concentration time courses of excitatory substances such as potassium and glutamate can be described with a reaction- diffusion equation. This equation contains four physiological parameters: (1) a concentration threshold for excitation; (2) a release rate; (3) a removal rate; and (4) an effective diffusion constant. Solving this equation yields expressions for the propagation velocity,...
Single neuron dynamics during experimentally induced anoxic depolarization - Zandt, B.; Stigen, T.; Haken, B. ten; Netoff, T.; Putten, M.J.A.M. van
We studied single neuron dynamics during anoxic depolarizations, which are often observed in cases of neuronal energy depletion. Anoxic and similar depolarizations play an important role in several pathologies, notably stroke, migraine, and epilepsy. One of the effects of energy depletion was experimentally simulated in slices of rat cortex by blocking the sodium-potassium pumps with ouabain. The membrane voltage of pyramidal cells was measured. Five different kinds of dynamical behavior of the membrane voltage were observed during the resulting depolarizations. Using bifurcation analysis of a single cell model, we show that these voltage dynamics all are responses of the same...
Generalized periodic discharges after acute cerebral ischemia: Reflection of selective synaptic failure? - Tjepkema-Cloostermans, Marleen Catharina; Hindriks, R.; Hofmeijer, J.; Putten, M.J.A.M. van
Objectives: Generalized periodic discharges (GPDs) can be observed in the electroencephalogram (EEG) of patients after acute cerebral ischemia and reflect pathological neuronal synchronization. Whether GPDs represent ictal activity, which can be treated with anti-epileptic drugs, or severe ischemic damage, in which treatment is futile, is unknown. We hypothesize that GPDs result from selective ischemic damage of glutamatergic synapses, which are known to be relatively vulnerable to effects of ischemia. Methods: We employed a macroscopic model of cortical dynamics in which we increasingly eliminated glutamatergic synapses. We compared the output of the model with clinical EEG recordings in patients showing GPDs...
EEG in silent small vessel disease: sLORETA mapping reveals cortical sources of vascular cognitive impairment no dementia in the default mode network - Sheorajpanday, R.V.A.; Marien, P.; Weeren, A.J.T.M.; Nagels, G.; Saerens, J.; Putten, M.J.A.M. van; Deyn, P.P. de
INTRODUCTION: Vascular cognitive impairment, no dementia (vCIND) is a prevalent and potentially preventable disorder. Clinical presof the small vessel subcortical subtype may be insidious and difficult to diagnose in the initial stage. We investigated electroencephalographic sources of subcortical vCIND in comparison to amnesic multidomain mild cognitive impairment (amdMCI) to determine the additional diagnostic value of quantitative electroencephalograhy (EEG) in this setting. METHODS: Fifty-seven community residing patients with an uneventful central neurological history and first presentation of cognitive decline without dementia were included, 35 patients were diagnosed with vCIND and 22 with amdMCI. A cognitive control group, deliberately recruited from a...
Inter-ictal spike detection using a database of smart templates - Lodder, S.S.; Askamp, J.; Putten, M.J.A.M. van
Objective: Visual analysis of EEG is time consuming and suffers from inter-observer variability. Assisted automated analysis helps by summarizing key aspects for the reviewer and providing consistent feedback. Our objective is to design an accurate and robust system for the detection of inter-ictal epileptiform discharges (IEDs) in scalp EEG. Methods: IED Templates are extracted from the raw data of an EEG training set. By construction, the templates are given the ability to learn by searching for other IEDs within the training set using a time-shifted correlation. True and false detections are remembered and classifiers are trained for improving future predictions....
Why Are Sensory Axons More Vulnerable for Ischemia than Motor Axons? - Hofmeijer, J.; Franssen, H.; Schelven, L.J. van; Putten, M.J.A.M. van
Objective:In common peripheral neuropathies, sensory symptoms usually prevail over motor symptoms. This predominance of sensory symptoms may result from higher sensitivity of sensory axons to ischemia.Methods:We measured median nerve compound sensory action potentials (CSAPs), compound muscle action potentials (CMAPs), and excitability indices in five healthy subjects during forearm ischemia lasting up to disappearance of both CSAPs and CMAPs.Results:Ischemia induced: (1) earlier disappearance of CSAPs than CMAPs (mean ± standard deviation 30±5 vs. 46±6 minutes), (2) initial changes compatible with axonal depolarization on excitability testing (decrease in threshold, increase in strength duration time constant (SDTC) and refractory period, and decrease in...
Thalamo-cortical mechanisms underlying changes in amplitude and frequency of human alpha oscillations - Hindriks, R.; Putten, M.J.A.M. van
Although a large number of studies have been devoted to establishing correlations between changes in amplitude and frequency of EEG alpha oscillations and cognitive processes, it is currently unclear through which physiological mechanisms such changes are brought about. In this study we use a biophysical model of EEG generation to gain a fundamental understanding of the functional changes within the thalamo-cortical system that might underly such alpha responses. The main result of this study is that, although the physiology of the thalamo-cortical system is characterized by a large number of parameters, alpha responses effectively depend on only three variables. Physiologically,...
Diagnostic decision-making after a first and recurrent seizure in adults - Askamp, J.; Putten, M.J.A.M. van
Purpose The role of EEG after a first seizure has been debated. Epileptiform EEG activity is a good predictor of seizure recurrence, but is reported in only 8-50% of first-seizure adult patients. Even if the EEG is abnormal, the opinions about treatment after a first seizure differ. The role of EEG in treatment decisions after remission or recurrence is also unclear. This study aims to identify neurologists' diagnostic strategies compared to guidelines about the use of EEG (i) after a first unprovoked generalized seizure in adults, (ii) after a recurrent seizure and (iii) in treatment decisions after recurrence or remission....