Jerald L. Varner

Neurophysiological efficiency in male and female alcoholics

Chronic alcoholics often exhibit impairment in behavioral indicators of cognitive efficiency. However, potential neurophysiological correlates of this deficit are understudied. To examine this function, semantic expectancy was measured by recording the N400 component of the event-related potential (ERP), which is elicited by incongruent semantic information. Abstinent alcoholics, 21-45 days sober (n = 26; 12 males, 14 females), as well as age and education equated community controls (n = 26; 12 males, 14 females), were instructed to read silently 218 sentences ending with either congruent, related/incongruent, or unrelated/incongruent terminal words. Difference waveforms to the terminal word were derived, and amplitude and latency measures of the most negative peak between 300 and 600 ms were obtained. Electrode sites included the midline sites, Fz, Cz, and Pz; the temporal sites T3 and T4; and parietal sites P3 and P4. Significant group effects in amplitude were observed for the difference waveform under the unrelated/incongruent condition at T3, T4, and P4 (P < or = .05). Measures at P3, Pz, Fz, and Cz approached significance (P < or = .15). Although the overall pattern did not change when regression techniques were used to control for age, only the T4 site retained significance (P < or = .05). Across all electrode sites, alcoholics produced reduced N400 amplitudes relative to community controls. Latency was unaffected. There were no group effects for amplitude or latency measures in the related/incongruent condition. These data are consistent with the hypothesis that alcoholics suffer from a subtle deficiency in neurophysiologically based cognitive efficiency which renders them less likely to respond appropriately to irrelevant information.

EEG during Masturbation and Ejaculation

The occurrence of a distinctive EEG pattern specifically related to sexual arousal and orgasm would provide a reliable and convenient means of identifying such events in the laboratory and would also provide clues to cerebral structures involved in the processes.EEG-polygraph recordings were obtained under rigorously controlled conditions in four normal male subjects during masturbation and ejaculation. The EEG data were subjected to both impressionistic and quantitative analyses. They showed no remarkable changes during the sequence of relevant physiological responses. The sole effect was a slight depression of alpha activity, a well-known nonspecific effect associated with changes in attention and arousal. Examination of the literature shows little agreement among reported results of studies of EEG changes during orgasm. It is likely that at least some reported changes were artifactual. It is concluded that the case for the existence of EEG changes specifically related to sexual arousal and orgasm remains unproven.

A Procedure For Automatic Classification Of EEG Genetic Variants

A procedure using spectral parameters for automatic classification of inherited EEG variants was investigated. Spectral parameters were calculated by extracting the poles of the transfer function derived from a fifth order AR model of the EEG. The visible form of each genetic EEG variant appeared to be determined by a dominant pole of the transfer function. Using classification rules developed from observing the spectral parameters of clearly defined EEG samples of each variant, twenty two EEG samples were processed. In a strict sense, there was a 59 percent agreement between the classification procedure and the impressionistic cl ass i f i cat i on indicating that the use of these spectral parameters is a viable technique for classifying EEG variants.

Interhemispheric synchrony in the EEGs of full-term newborns

Cross correlations between 4 homologous pairs of ear-reference derivations were calculated for 45-sec digitized samples of typical active and quiet sleep in 19 selected normal newborns at 21--70 h after term birth. Repeat recordings were obtained in 9 subjects 24 h after the original recordings and another set of cross correlations was calculated. For comparison, similar recordings were obtained from 4 asymptomatic young adults and cross correlations were calculated for 45-sec samples of typical stage 4 and stage REM sleep and for stage W both before and after sleep. Mean cross-correlation coefficients at zero time lag were generally higher for the adult sleep data than for the newborn data, but the differences were smaller than had been anticipated. The coefficients for active sleep data in the newborns were higher than for quiet sleep data, while in the adults the coefficients were higher for stage 4 than for stage REM. Coefficients were higher for convexity derivations than for temporal derivations in both newborns and adults. A review of the small available literature suggests that recording and analysis techniques may be significant variables determining the results obtained in such studies. The cross-correlation method of measuring interhemispheric synchrony may prove useful in identifying brain disorders in the postnatal period.

Interhemispheric amplitude symmetry in the EEGs of normal full term, low risk premature, and trisomy-21 infants ☆

RMS measurements of amplitude symmetry were calculated for samples of typical active and quiet sleep periods in 12 normal full term, 5 premature and 7 Trisomy-21 infants from recordings obtained at 1, 4, 12 26 and 52 weeks post term. The frequency distributions of the symmetry data for each group did not deviate significantly from the expected normal distributions. The mean symmetry ratios were not significantly different among the 3 groups. It was concluded that the EEGs of the 3 groups are characterized by amplitude symmetry in the first year of life. The possibility that symmetry data may be used for classification of abnormal EEGs was discussed.

Attention Deficits In Alcoholic Brain Syndrome

An intensive study of alcoholic organic syndrome patients has been carried on using the 0 wave components of the event-related potential as an electrophysiological measure. from auditory passive and discriminate tasks and a visual discriminate task on normal, Korsakoff, and alcoholic dementia patients. The frontal negative 0 wave was observed to be greatly enlarged in alcoholic organic brain syndrome patients. enlargement is believed to be an indication of an attention failure, specifically a failure to regulate the orienting response, and this failure may reflect a frontal lobe dysfunction. Data was measured

Evoked EEG gamma band response at slow rates of stimulation

We have sought to confirm the observations of an auditory gamma band response and study the effects associated with several stimulation parameters including ear of stimulation, stimulus intensity and frequency, and rate of repetition. The data confirm the presence of a burst of activity, within the gamma band, following auditory stimuli and suggest that the response is intimately, and specifically, related to fundamental auditory processes.

A Laboratory Experience in Probability and Random Processes

Laboratory experiments for a junior level course in probability and random processes are described. The laboratory is hardware based and uses the Telecommunications Instructional Modeling Systems (TIMS). All of the laboratory experiments are available for download from http://www.nuengr.unl.edu/issl/. Summaries of student feedback concerning the laboratory are provided

Work in progress: a TIMS based laboratory for undergraduate probability and random processes

Laboratory experiments for a junior level electrical engineering course in probability and random processes are described. The laboratory platform is centered on the telecommunications instructional modeling systems (TIMS). All of the laboratory protocols are available for download from the first authors Website.

A simple technique for eye blink correction

The ability to correct for ocular artifacts in EEG signals recorded during the course of event-related potential experiments is of major importance. The basic principle used when correcting ERPs with recorded EOG signals is to consider the ocular artifacts as a linear combination of the measured EOG signals and to subtract these ocular artifacts from the measured ERP signals. This pcrper describes a simplified method for calculating EOG correction coefficients for eye blinks. Preliminary resu l t s of applying this technique to the EEG data of seven children have shown a significant increase in the number of usable trials available for computing averages.