Visually evoked potentials of 215 subjects, aged 1 month to 81 years, were studied. Amplitudes of waves in the first 250 milliseconds of the response changed markedly with age. In responses recorded from the occiput, there was a rapid increase in amplitude reaching a maximum in the 5- to 6-year-old group, with means of amplitudes at this age being about twice as large as means of some older age groups. With children 7 years and older there was a rapid decline in amplitude until ages 13 to 14, when an abrupt increase in amplitude appeared. Amplitude appeared to stabilize at about age 16. In older subjects, mean age 60 and beyond, significant changes were noted in the earlier components of the response.

Adolescent↗

PubMed1966

Hypnotic suggestions and visually evoked potentials.

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Adolescent↗

PubMed1965

The visually evoked potential in twins.

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Adolescent↗

PubMedDate not supplied

Sustained ingestion of delta 9-tetrahydrocannabinol and the operant behavior of stump-tailed macaques.

Three stump-tailed macaques were trained to press a lever for liquid reinforcement on a tandem schedule which required the animal to delay responding for at least 30 sec after each reinforcer. If the animal responded during that interval, a clock was reset thus re-establishing the delay requirement. If he delayed responding appropriately, the monkey was shifted to a fixed-interval schedule of 135 sec duration. The FI component was terminated with a drop of flavored liquid at which point the delay requirement began anew. Following a stable baseline performance, two monkeys received 2 mg/kg of THC orally every third day for 90 days with the placebo administered on intervening days. The third animal received the placebo throughout testing. Each monkey's performance was described in terms of response rate and response patterning between reinforcers. Despite the sustained ingestion of THC neither animal showed appreciable change in test behavior attributable to tolerance to the drug. Although the drug continued to have a powerful effect throughout testing on the days it was administered, there was no evidence of any consistent or cumulative drug effect on placebo-day performance.

Animals↗

PubMedDate not supplied

Age and fitness effects on EEG, ERPs, visual sensitivity, and cognition.

Measures of EEG, event-related potentials (ERPs), visual sensitivity, and cognition were obtained from 30 young (20-31 years) and 30 older (50-62 years) healthy men. Age groups were evenly divided between subjects with low and high fitness levels documented by VO2max during a maximal exercise test. Age comparisons revealed that, compared to young adults, the older men had reduced visual sensitivity, delayed ERP latencies, greater homogeneity of EEG activity across recording sites, more positive visual-evoked potential (VEP) amplitude-intensity (A/I) slope, and poorer performance on a battery of neurocognitive tests. The EEG and VEP A/I slope findings are believed to reflect weakened central inhibition for the older men. In general, the measures that differentiated groups on the basis of age were also sensitive to differences in aerobic fitness. Compared to low fit men, the physically active men had shorter ERP latencies, stronger central inhibition, better neurocognitive performance, and better visual sensitivity. We speculate the performance superiority of the physically active men was, at least in part, the result of more oxygen being available for cerebral metabolism.

Adult↗

PubMedDate not supplied

EEG, visually evoked and event related potentials in young abstinent alcoholics.

EEG, visually evoked potentials (VEP), and event related potentials (P300) were recorded from 60 males aged 25-40 (20 abstinent alcoholics, 20 social drinkers, and 20 lifetime nondrinkers). Alcoholics were at least 1 month abstinent, medication free, and neuropsychologically normal. Residual effects of alcohol abuse were not detected in EEG power and cortical coupling analyses, or VEP amplitude, latency, and amplitude/intensity slope measures. Only P300 measures, recorded while subjects were actively engaged in a visual oddball task (20% targets), differentiated alcoholics from nonalcoholics. Alcoholics had reduced N2-P3 amplitude and delayed N2 latencies compared to social drinkers and nondrinkers. Because P300 abnormalities have been reported for individuals with positive family history for alcoholism, it is not clear whether these results reflect familial influence or residual effects of alcohol abuse. Issues relating to age, health and medication status of abstinent alcoholics, and use of social drinkers as comparison groups in studies of brain dysfunction in "recovering" alcoholics are also discussed.

Adult↗