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J L Varner

Publications and source records attributed to J L Varner.

23 records · Page 2Linked to original sources
PubMed1981

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.

Down Syndrome↗
PubMed1978

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.

Age Factors↗
PubMedDate not supplied

Dose-related effects of ethanol on visual sustained attention and event-related potentials.

The effects of acute ethanol intoxication on visual sustained attention were investigated in male social drinkers. Four doses ranging from 0 (placebo) to 1.05 g/kg lean body weight, with periodic maintenance dosing of 0.12 g/kg, were given in separate sessions. The task required subjects to monitor a series of blurred digits presented singly at a rate of one per sec and to respond to occasional (p = 0.25) target digits with a speeded button press. Detection performance deteriorated as a function of both dose and time on task. In addition, the factors of dose and time on task interacted to produce a more rapid performance decrement under the higher doses. Early event-related potential (ERP) components (N1 and P2) were not greatly affected, suggesting that the performance decrement reflects central rather than peripheral factors. Later components related to cognitive appraisal processes (N2, P3), in contrast, varied in both amplitude and latency. Ethanol yielded dose-related delays in N2 and P3 latencies, which paralleled reaction time increases. The amplitude of N2 also decreased over time on task, and P3 amplitude decreased both as a function of dose and time on task. ERP and performance data were interpreted as demonstrating an adverse effect of ethanol on central processing capacity.

Adult↗