Nathan W. Perry

Detection of Guilty Knowledge with Event-Related Potentials

The N400 component of the event-related potential (ERP) is elicited by words that complete sentence falsely. The utility of the N400 in discriminating subjects who have knowledge of a crime from those who do not was examined in this study. Post hoc analyses indicated that 78% of subjects could be correctly classified as guilty or innocent. With further development, ERPs may become useful auxiliaries to current lie-detection techniques.

Classification of Cortical Responses Using Features from Single EEG Records

Our research goal is to develop a new methodology for studying brain function using single, unaveraged EEG records. This investigation has led to a new algorithm for feature extraction for the case of small design (learning) sets. The algorithm has been applied to extract features from unaveraged (single) EEG records, which consist of single evoked responses elicited from human subjects who read textual material presented in the form of propositions. The subjects were instructed to make a binary decision concerning each proposition. This gave two possible data classes. We selected features from the evoked event-related potentials (ERPs), and designed a classifier to assign the ERPs for each proposition to one of the two possible classes.

Spatio-temporal measures of cortical functioning in normal and abnormal vision

Abstract Computer-generated displays of scalp-monitored spatiotemporal potential field patterns evoked by visual stimulation are used to demonstrate that dysfunctions in the visual system can be detected. Such dysfunctions may go unnoticed unless adequate spatial sampling is performed. Various display techniques are presented and discussed. These displays and similar techniques have application in the investigation of numerous and diverse electrophysiological phenomena.

Relations of Scores on WPPSI and WISC-R at a One-Year Interval.

This study was designed to provide information regarding the relationship between the WPPSI and the WISC-R, over a 1-yr. interval, for a sample of middle-class children of above average intelligence. There were 47 males and 43 females who were an average of 5.6 yr. at the time of first testing and 6.5 yr. at the time of second testing. The data, analyzed by a linear regression analysis, showed that the WISC-R Verbal, Performance, and Full Scale IQs could be predicted with a reasonable degree of accuracy, i.e., standard errors of estimate: Verbal IQ = 8.86, Performance IQ = 8.15, Full Scale IQ = 7.14. The results were discussed in terms of the degree of similarity between cognitive skills measured by the two tests and the clinical utility of such information.

Chromatic Specificity of the Visual Evoked Response

The temporal alternation of red and green stripes in a structured field produces successive contrast, which can elicit cortical potentials recorded from the scalp. Amplitudes of the major frequency components of the potentials correspond to the relative intensities of red and green producing the contrast. The amplitude variations are color-specific, since total luminance and structure are held constant.

Ensemble Characteristics of the Human Visual Evoked Response: Periodic and Random Stimulation

Most investigations of visual evoked potentials monitored at the human scalp have utilized the average of a series of responses recorded from a single subject in a specific population to define components of the visual evoked response (VER). While this technique provides a fairly consistent estimate of an individuals average VER, it is not uncommon to obtain quite dissimilar averages from different subjects under identical experimental conditions. This contrast in the VER estimates across a population has hindered the interpretation of the effects of stimulus parameters on the VER and frustrated the attempt to use this average for clinical diagnosis.

Human cortical correlates of color with monocular, binocular and dichoptic vision

Abstract Five subjects (three normals, one amblyope and one deuteranope) were presented red (630 nm), yellow (577 nm), green (520 nm), and achromatic stimuli twice in all possible monocular and binocular combinations. Four averaged visual evoked responses were simultaneously recorded over four scalp areas to each stimulus condition, giving 224 VERs for each subject. Color coding was found in all normal subjects over a large scalp area above the occipital cortex and was questionable with the deuteranope. Most marked color coding (changes in waveshape of the VER produced by the different wavelengths) occurred late in the VER (> 215 msec). It was possible to examine the contribution of each eye to the cortical response during binocular stimulation.

DIFFERENTIAL CORTICAL HABITUATION WITH STIMULATION OF CENTRAL AND PERIPHERAL RETINA

A digital computer extracted and quantified cortical evoked potentials recorded from the scalp of man in response to repetitive light stimulation. The habituation of potentials from stimulation of the central retina was compared with habituation of potentials from stimulation of two peripheral retinal areas. Habituation was more rapid to peripheral stimulation and also significantly greater.

Multichannel, Single Tral Event Related Potential Classification

We report on the effect of electrode placement and number of electrodes on the classification of single trial event related potentials (ERPs). The subjects read propositions relating fictitious people and their occupations while ERPs were recorded. The subjects decided if the proposition was correct or incorrect and responded as per instructions. The single trial, multichannel ERP data were classified using various methods, e. g., hold-out, leave-one-out, resubstitution. Several other factors were examined to determine their effect on ERP classification, including taking a majority vote among channels, using the single best channel, and averaging the data across channels for a single ERP. The results from other experiments are compared to those presented here.

A Yudin-type short form of the WISC-R: two aspects of validation.

Provided validity data for a Yudin-type short form of the WISC-R for N equal to 70 middle-class children (34 males and 36 females, X age equal to 7.6 years, SD equal to 2.58 months) of above-average intelligence (means: VIQ equal to 115.55, PIQ equal to 122.27, FIQ equal to 121.02). Short- to long-form validity coefficients were all above .90 for Verbal, Performance, and Full Scale IQ scores. Highly similar predictive validity coefficients were found for the short and long forms of the WISC-R when compared with the Metropolitan Achievement and Otis Lennon Mental Ability tests. In contrast, little support was found for the validity of the short-form profile data as assessed by Cattells rp coefficient of profile similarity.