T. Radil-Weiss

Some comments on the derivation of the Wiener filter for average evoked potentials.

The Wiener filtration of average evoked potentials supplies the estimate of evoked response with the least square error. However, this error is dependent on the choice of interstimulating intervals. This dependence was not considered in hitherto applications of the Wiener filter. In this paper the Wiener filter with respect to the concrete choice of interstimulating intervals is derived.

Wiener filtration versus averaging of evoked responses

The extraction of the evoked potential by the Wiener filtration technique is performed to compare it with classical averaging. It is well known that the Wiener filter supplies the least square error estimate. On the other hand, it is apparent that this error substantially depends on the choice of the lengths of interstimulation intervals. Artificially simulated examples are processed by both techniques, averaging and Wiener filtration, to show that the proper choice of the interstimulating intervals is much more relevant for decreasing the estimate error than in helping us make the decision which of these methods should be used.

EEG alpha and non-alpha intervals alternation.

In human subjects with closed eyes and limited external influences the spontaneous alternation of alpha and non-alpha intervals was recorded. It was found that duration of alpha periods fits the shifted exponential distribution. A mathematical model based upon the theory of queuing has been designed explaining the empirical data.

Scanning open and closed polygons

The process of selection of target points during voluntary eye movements when contoured polygonal shapes with open and closed angles are observed was analysed in humans by means of an eye recording technique. It has been found for both types of stimuli that the majority of fixation points where located at angles and that the mean value of distribution was found to be more distant from the vertex for acute angles than for obtuse ones. In this respect a difference was found between open and closed contours. In the former case the mean values of fixation point distribution were more distant from the vertex and the dispersion of eye fixation was greater.

Target point selection during scanning eye movements

The process of selection of target points during voluntary eye movements when polygonal random shapes are observed was analysed in humans by means of an eye movement recording technique. A computer model was constructed with the aim to explain the empirical results. It has been found that the majority of fixation points were located at the angles. The marginal distribution over the x-axis of the individual angles depends on the angles size: the maximal value of distribution was found for acute angles more distant from the vertex than in obtuse ones. The distribution of output activity of the “ganglion cells” in a computer model, reproducing some basic features of the retina, is in good agreement with the empirical results.

A generalization of the Yule-Simon model, with special reference to word association tests and neural cell assembly formation

Abstract A generalization of the Yule-Simon model is suggested and such related questions as inversion problems and nonequilibrium behavior are solved. The generalization follows the work of Haight and Jones ( Journal of Mathematical Psychology , 1974, 11, 237–244) and thus special reference is made to word association tests. Some new possible applications of the presented model are offered, namely, in the field of neural cell assemblies.

OCULOMOTOR AND COGNITIVE ASPECTS OF VISUAL PERCEPTION

Publisher Summary This chapter discusses the oculomotor and cognitive aspects of visual perception. It analyzes objectively the internal processes during human visual perception and cognition, which are of subjective nature. The experimental design in perception and cognition research is usually based upon the assumption that the perceiving system can be analyzed by comparing the responses recorded with the stimuli varied by the experimenter according to certain rules. Analyzing statistically serial dependences concerning the length of time intervals corresponding to both types of subjective interpretation of the Necker cube patterns, it has been found empirically that neighboring intervals tend to be of similar duration. This is valid for both types of interpretation separately, and for the neighboring intervals of different type. As both types of processes take place within the same system, their mutual influence and interrelations do not require the existence of any mediating interface. As conscious phenomena are attributes of the complex neuronal matter, they cannot be dissociated from it.

Average evoked brain potential comparison on the basis of spectral and coherency functions.

A technique of quantitative comparison of pairs of average electroencephalographic evoked potentials on the basis of their spectral and coherency functions computed by means of a laboratory computer is described. Both theoretical consideration and results of testing the method with computer generated arteficial signals and real average evoked potentials are given.

Estimation of Evoked Potential by Wiener Filtration

Summary The Viener filtration of a stationary signal from a mixture composed of the signal plus a stationary noise has an application when extracting real evoked potential from poststimulation EBG records. The Wiener extraction became a competitive method with the simple averaging. Both methods, i. e. Wiener filtration and averaging, are compared with respeot to elucidade relations between results obtained by them.