Threshold adaptation for mean value based operant conditioning. - In: 2005 27th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, (2005), S. 3612-3615
Biofeedback and a variety of brain-computer-interface methods imply as very first stages the obtainment of control of selected signals e.g. the related generating psycho- physiological processes. The basic mechanism in the learning phase is the operant conditioning, which represent a complex behavioral method consisting of several components. One of the most important components is the setting and adjustment of thresholds for the triggering of corresponding rewarding options. An adaptive threshold optimization method, for the training based on average values is presented. The procedure is derivated from the sequential test from Wald. The application of the sequential tests in the learning/training process allows a threshold adaptation corresponding to the abilities of the particular person and to the learning success. - Keywords- operant conditioning, brain-computer-interface, learning, sequential methods.
Comparison of time-variant coherence algorithms in single-trial: a dynamic analysis. - In: 2005 27th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, (2005), S. 5647-5650
Synchronization in the electroencephalogram, which can be quantified by time-variant coherence measures, reveals a communication between brain regions reflecting different functions (e.g. learning or memory). Aim of this work is to compare three time-variant coherence algorithms in single-trial. The first algorithm is based on the short-time Fourier transform, the second one on the adaptive discrete Fourier transform, whereas the third algorithm is based on a recursive smoothed pseudo Wigner-distribution. Parameters which describe the dynamic properties of the algorithms were calculated and compared on simulated data. Differences were observed in the estimation performance of the algorithms. Based on the obtained results, the algorithms are discussed for their utilization in future applications. - Keywords- Time-variant coherence, short-time Fourier transform, adaptive discrete Fourier transform, pseudo Wigner-distribution
Evaluation of feature extraction algrorithms for the feature-list cross-correlation in retinal images. - 6 S. = 280,2 KB, TextCD-ROM-Ausg.: EMBEC '05 : 3rd European Medical and Biological Engineering Conference, November 20 - 25, 2005, Prague, Czech Republic / International Federation for Medical and Biological Engineering. - Prague, 2005, IFMBE proceedings ; 11
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First results of VEP measurement with a gaze controlled perimeter. - In: EMBEC '05, (2005), insges. 4 S.
Extension of vessel model for the validation of retinal vessel analysis. - In: EMBEC '05, (2005), insges. 4 S.
Diagnostics of peripheral arterial occlusive disease using different classification strategies in association with impedance plethysmographical features. - In: EMBEC '05, (2005), insges. 5 S.
Methodology and first results of selective cone stimulation of human eye via silent substitution technique. - In: EMBEC '05, (2005), insges. 5 S.
For electrophysiological examination of colour vision defects and of wavelength specific neural pathways, selective excitation of cones is needed [1]. Physical impulses have to give a desired effect at psychophysiological level. By use of appropriate colour models associated with the silent substitution technique these possibilities are given [2], [3]. For generation of suitable stimulations via silent substitution technique all kinds of display - colours, given in the RGB space, must be mapped onto the biological system of L -, M - and S - cones. Thus at certain combinations of colour the activation of the cones is known. By calculating of different colour combinations the activation of different cones types can be modified. With these calculated colour values a flash stimulation sequence for a TFT - display was generated. The first examinations are accomplished at test persons. Two trials (S - cone and L and M - cone response) at both eyes accomplished. The analysis of the VEP data in the EEG shows a significant delay of the S - cone response against the L - and M - cone response. First results show that it is possible to excite the cones selectively via silent substitution technique. Further investigations in this field, at more test persons, are necessary to verify the results and generalise the electrophysiological effects.
Spectral distribution and dynamics of stimulators for selective cone excitation. - In: EMBEC '05, (2005), insges. 5 S.
For early detection of eye dysfunctions which are caused by glaucoma, optic neuropathy and other forms of ophthalmic and neurologic pathology a selective cone excitation on biological level is necessary. By the use of a RGB-stimulator which enables a free choice of stimulation-colour and pattern it is possible to isolate the specific cone type responses. The right choice of a practical stimulator is very important for a high efficiency of the cone excitation. In our investigations we used two selection criteria - the spectral properties inclusive the effects on the biological level and the dynamic behaviour at the screen change for a stimulation sequence. For an easy handling with the stimulator and for a simple realisation of stimulation sequences, the tested RGB-systems are commercially available. After the investigation of the spectral and dynamic properties we could find a suitable cone stimulator.
Comparison of phase coupling parameters for the analysis of neuronal synchronization. - In: EMBEC '05, (2005), insges. 4 S.
Instructions for preparing papers for IFMBE Proceedings Series are presented. They are intended to guide the authors in preparing camera-ready hardcopy and electronic form of their papers. Only papers prepared according to these instructions will be published. (MAX 200 words)The investigation of large-scale neural integration by synchronization is essential for the understanding of the brain organization [10]. Up to the present, transient phase synchronization is one of most suitable concepts for a neural interaction process explanation. This paper deals with the quantification and detection of the bivariate phase coupling. Here the most applied phase synchronization parameters in neuroscience i.e. phase locking value (PLV) [2] as well as Shannon entropy parameters [1] [3] are compared. The features of these approaches can directly be tested on generated circular data without estimating instantaneous phases. For this purpose, instantaneous phase sets with defined probability distributions are generated. The results of the study show that the PLV represents the most suitable analysis method for detecting phase synchronization in noisy signals.
Modelling and simulation of clinical processes by the example of the "acute coronary syndrome". - In: EMBEC '05, (2005), insges. 4 S.
In the health service a comprehensive instruction for each illness, which illness needs which diagnostics and which therapies, exists. The acute coronary syndrome represents such a clinical process. In the available paper this clinical process from medical view is arranged. In order to be able to model afterwards this clinical process, the necessary process structures must be put on such as systems, modules or primitives in using the MLDesigner. Subsequently, a model can be produced from the individual structures. The compiled model is evaluated in the connection according to criteria of modelling. Friendliness, correctness, reusability by model elements or the possibility of structuring are estimated. The developed simulation model can be used after completion for the analysis of the process of the acute coronary syndrome, in order to determine bottlenecks and dependence between individual process steps. Subsequently, it applies to find out by resources increase in the individual bottlenecks, which increase is useful for the minimization of the total waiting period of the patient.