Michael Yost

Fourier analyses: A mathematical and geometric explanation

Fourier analyses are used in electrophysiological research to reduce EEG data to an interpretable, analyzable form. This article outlines the mathematical similarities and differences between Fourier transforms and fast Fourier transforms. A geometric explanation of the application of fast Fourier transforms and a Fourier series to theta-band EEG data is also included in this article.

Computer-managed inferential statistical analysis of EEG data

Much of the neuroelectrical/psychophysiologic research of the past has involved the use of “group-type” statistics. Often, this has resulted in large variances that make it difficult, if not impossible, to find significant differences. Using the INNOVATE technique of single-subject design, we are able to consistently demonstrate significant differences in EEG spectra related to experimental and clinical effects previously masked.

The Use of Computer Networks in Data Gathering and Data Analysis.

In our research, the data are gathered in the laboratory on a DEC PDP-11/24 minicomputer. Once the data are gathered, they are analog-to-digital (A/D) converted and sent by the PDP to an IBM 370-3031. The data are submitted to a Fast Fourier Transform (FFT) on the IBM computer. Once the FFT is completed, the data are accessed by an IBM PC-XT that is equipped with an IRMA system. The PC is used in its emulation mode to access the data in the mainframe. In the mainframe, SPSS or SAS is used to do the initial statistical analyses. When necessary, subsets of the data are transferred to the PC, where other computer programs are used to analyze the data. In many instances, they are returned to the mainframe from the PC, where they are submitted to multivariate statistical analysis. Finally, all of the data are stored on floppy disks, which are prepared on the PC.

Assessing the simulation of chaotic systems

Three commercially available software packages—BrainMaker, MicroSaint, and Extend—that simulate the function and operation of neural networks were compared on 11 dimensions. Also, a task-oriented analysis was done on the ability of the programs to use a neural network to output a chaotic array generated by the logistic equation. There were differences in the amount of operator overhead among the programs, but the differences in the simulation performance were not considered to be appreciable.

Using three-dimensional graphics in neuropsychological hypothesis testing

This paper presents the application of an overlapping sampling technique used with a fast Fourier transform on electroencephalographic data. The use of this sampling and analysis technique is demonstrated on data in which steady state, rate of change, and critical event hypotheses are tested. The benefit of applying computer-generated three-dimensional graphics to the results of using this innovative sampling and analysis technique is emphasized.

A longitudinal study of cardiac component analysis

The purpose of this study was to examine the reliability of a physiological event over several weeks. The physiology analyzed was the electrical event of the heart. Two operationally defined components of the typical heart response were examined. The technique gave very reliable data within a given day. Moreover, when the data for 20 weeks were added, the overall standard deviation was very small, but there were unpredictable physiological variations from day to day. The data suggest that comparisons between psychological tasks using physiological events as the dependent measure are best done in close temporal contiguity.

Microcomputer, minicomputer, mainframe interfacing

The problems associated with the transfer of data from one computer to another in conducting neuropsychological research are described. The reasons for using different computers to perform different tasks are outlined, and a rationale for using task-specific computers is presented. A detailed description of the use and function of the Kermit File Transfer Protocol in neuropsychological research is given.

Multivariate statistics and three-dimensional graphics

This paper describes the process by which a system of three-dimensional computer-generated graphics was developed for use by students and researchers in analyzing multivariate psychological data. Examples of the application and use of the system in analyzing factor analytic and discriminant analysis data are presented. Details on the operation of the system are also included.

The effect of smoothing functions on data obtained from a FFT

This research investigated the effect on power spectra when data-smoothing functions were used on EEG data prior to submitting them to a FFT. We used two smoothing function options: not using any smoothing function and using the Parzen smoothing function. We developed a program to evaluate each of these functions with real and standard data. When a set of data is submitted to smoothing prior to being submitted to a FFT, there are statistically significant differences in the power spectra obtained from the FFT. This finding holds true for standard waveforms as well as for real EEG data.

Statistical analysis of fuzzy-set data from neuronal networks

In this study, we describe the process of transforming neuron polarization values that meet the assumptions of ratio data into ordinal data. This is a crisp-to-fuzzy set transformation. A computerized simulation of the application of this process is discussed and nonparametric methods of analyzing fuzzy-set data are presented.