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In psychophysics, the response to a stimulus is usually limited to a single value during some time interval. Moreover, the response is usually quantified, e.g., binary (yes or no). Such data is very limited information for parameter estimation. A particular example is the response to a sensory stimulus where we vary one stimulus profile around a threshold. Instead of the psychophysical threshold we aim to estimate parameters of a neurophysiological model, given the input-output data using different experimental profile settings.

In the intensive care unit (ICU), patients are often sedated and ventilated, which makes clinical evaluation of the status of the brain very limited. In these situations, the EEG is a potentially very useful tool to be informed about the status of the brain. EEG rhythms are very sensitive for derangements in brain function, as may occur in hypoxia, and can reliably detect epileptiform discharges. In addition, it can be a valuable tool for follow-up of patients, and can significantly contribute to prognostication of brain-damaged patients. The actual use of continuous EEG monitoring in the ICU is limited, however. An important contributing factor is related to the difficulties in interpreting the raw EEG signal, that does not permit a straightforward understanding by nontrained personnel. We recently proposed a visual transform of the EEG (van Putten, J Clin Neurophysiology 2008; 25:63–68) to facilitate the interpretation. Here, we present a modification of this analysis, including examples of this method in monitoring patients in the ICU.

When modeling complex systems such as the cardiovascular circulation one often needs to separate the problem into smaller subproblems because of the heterogeneous nature of the system and/or the modeling techniques. The application at hand is to link blood flow in an artery to that in the circulation. The artery of interest is modeled by a 3D CFD model that includes a model for the elastic wall to simulate fluid-structure interaction. This 3D arterial model is coupled to a 0D model (electric network) for the cardiovascular circulation. We show that the weak coupling method is numerically unstable for this application. Using a simple model problem, a theoretical stability analysis is performed which explains the instability of the simulation results. Additionally, we consider fluid-structure interaction in an elastic artery. Again stability analysis results in a theoretical (in) stability condition that is in good agreement with simulation results. As a solution for these stability problems the quasi-simultaneous method is presented. The big advantage over strongly coupled methods is its low computational cost.

Introduction: Despite state of the art tracheo-esophageal (TE) voice-rehabilitation after laryngectomy, some patients are unable to produce voice of sufficient quality, because of hypotonicity or atonicity of their pharyngo-esophageal (PE) segment. Furthermore, the TE voice is low pitched, which presents a problem especially for female laryngectomized patients. A voice-producing element (VPE) is developed, based on the double-membrane concept, to supply the laryngectomized patients with a better substitute voice. Materials and methods: The VPE is comprised of two elastic membranes inside a circular housing that can be inserted in a shunt valve. Four identical prototypes were manufactured and tested in-vitro under physiological conditions. Prototypes were also tested in 17 female laryngectomised patients. An aerodynamic and acoustical analysis was performed, the maximum phonation time, speech rate and intonation capability determined. Finally the voice was perceptual evaluated. Results: Basic sound, containing multiple harmonics, was successfully produced under physiologic air pressure and airflow conditions. The fundamental frequency and sound pressure level could be controlled by changing the driving pressure, thus enabling sufficient intonation. The obtained frequency range (190 - 350 Hz) is appropriate for producing a female voice. The VPE produced a sound with a low noise-to-harmonics ratio (mean 0.15), the efficiency of sound production (5.5.10(-5)) is comparable to normal vocal folds. The clinical study clearly showed that the pitch and sound intensity were increased without an unacceptable increase in driving lung pressure. The flow rates were lower than normal, leading to significantly longer phonation times. Accumulation of mucus did not interfere with speech production. Conclusion: Functional restoration of the voice after laryngectomy with a VPE, based on the double-membrane concept, appears a feasible concept for female laryngectomized patients or patients with a hypo-or atonic PE segment.

Tremor and bradykinesia are two prominent features of Parkinson's disease (PD). This paper presents the PD monitor, a measurement system using accelerometry to quantify tremor and bradykinesia. A correlation analysis of the physician's scores and the PD monitor demonstrated that the system accurately measured the severity of tremor and bradykinesia whilts assessing a broad spectrum of aspects related to both symptoms. In conclusion the PD monitor can be used for a detailed evaluation of the PD monitor symptoms in order to optimize treatment.

Deep Brain Stimulation (DBS) in subthalamic nucleus (STN) has substantially improved the suppression of symptoms in Parkinson's disease (PD). However, a quantitative understanding of the high-frequency stimulation opn the neuronal elements surrounding the electrode and the resulting effects for the different symptoms for upper and lower extremities is missing. The aim of the study is to investigate if there is a somatotopic organisation of the STN.

In order to improve observability of the processing of nociceptive and tactile stimuli, a new electrocutaneous stimulation electrode was developed. The electrode aims at combining the exact timing of electric stimulation with preferential activation of nociceptive or tactile afferents. In order to determine the effect of stimuli applied through the bimodal electrode on subjects, a characterization study was perfomed. The needle electrode sensation thresholds were lower than the flat electrode thresholds. The subject averaged quality VAS score was significantly influenced by mode, the intensity score by NoP. The EP's were significantly influenced by both mode and NoP and suggest a difference in processing between the modes.

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