Vitamin-mineral supplement fails to improve IQ of mentally retarded young adults.

Twenty mentally retarded persons participated in a study to determine the effect of large doses of vitamin-mineral supplements on IQ, educability, electrophysiological responsiveness, and pyridoxine metabolism. Using a double-blind matched group experimental design, we administered supplements and placebos for 6 months. Pre- and postmeasurements showed no significant effects on any of the measured variables.

Down syndrome individuals fail to habituate cortical evoked potentials.

Small sample cortical evoked potentials in response to repetitive auditory stimuli were recorded from 10 Down syndrome individuals and from 10 nonretarded persons whose initial evoked potential amplitude was equated with that of the Down syndrome subjects in a matched-pairs experimental design. Regression analysis of sequential evoked potential amplitude revealed that the nonretarded subjects showed rapid habituation of their cortical evoked potentials whereas the Down syndrome subjects failed to show habituation. The findings support the concept of a deficit in inhibitory capacity at the fundamental electrophysiological level as a substrate for the behavioral-cognitive impairment characteristic of Down syndrome individuals.

Knowledge of stimulus timing attenuates human evoked cortical potentials.

To determine whether or not knowledge of stimulus timing influences the amplitude and latency of evoked cortical potentials, we have studied the evoked potentials of 24 adults under two contrasting conditions in which people knew or did not know the timing of tone stimuli by means of numerical perceptual cuing. Results demonstrated markedly smaller amplitude and significantly faster latency for the late components of vertex potentials evoked by stimuli whose timing subjects knew in advance. The cognitive act of knowing when auditory stimuli will occur attenuates the amplitude and facilitates the poststimulus timing of cortical evoked potentials.

The chronic toxicity of 3-chloro-4-methyl benzamine HCl to birds.

3-Chloro-4-methyl benzamine HCl (DRC-1339), an avian toxicant, was fed to five species of birds for periods up to 120 days. The 30-day LC50 of uniformly treated feed for starlings was 4.7 ppm and the 90-day LC50 was 1.0 ppm. The 28-day LC50 for coturnix was 18 ppm. The 30-day LC50 for pigeons was less than 100 ppm. Pheasants fed diets containing 2% DRC-1339 baits diluted to a rate of 286 ppm of DRC-1339 died within 22 days. Bobwhite quail fed similar diets suffered some mortality at levels as low as 2.9 ppm, but most survived 10 times this dosage level for the 120-day test period. Application of the Kenaga "Index of Chronicity", resulted in the conclusion that DRC-1339 was cumulatively toxic to birds. Reproduction in coturnix was adversely affectd by treatments at 10 ppm of DRC-1339 and above. Reproduction in pigeons was adversely affectd by a treatment of 25 ppm. In coturnix, DRC-1339 caused an increased incidence of egg breakage and decreased both egg and live chick production. In pigeons, DRC-1339 caused an increase in the proportion of infertile eggs. Reproductive ability to first generation offspring was not affected when parent coturnix and pigeons were fed DRC-1339. These data emphasize the need for care in the use of DRC-1339. The bait should be used only as registered and care exercised in storage and disposal of unused baits to avoid poisoning of nontarget species.

The chronic toxicity of methiocarb to grackles, doves, and quail and reproductive effect in quail.

Methiocarb (4-methylthio-3, 5-xylyl N-methyl carbamate, Mesurol, Bay (3744), a bird repellent, was fed in concentrations of 100 to 1,000 ppm to common grackles (Quiscalus quiscula), mourning doves (Zenaida macroura), and breeding pairs of coturnix quail (Coturnix coturnix) to investigate the possibility of cumulative intoxication. Although aversion to treated diets was readily apparent in most of the tests, the 28- to 30-day median lethal concentration (LC50) was determined to be greater than 100 ppm for grackles, 630 ppm (95% confidence limits, 480-830 ppm) for doves, and greater than 1,000 ppm for coturnix quail. Methiocarb appeared to be noncumulative when measured by an index of chronicity: birds consumed several LD50 doses during a day's feeding, and when deaths occurred, they appeared to be due to acute intoxication. Egg production and live chick production were not affected in coturnix fed 100 ppm but were reduced at 316 and 1,000 ppm.

Evidence that monoamines influence human evoked potentials.

We have measured latency and flash/pattern differentials of the visual evoked potential (VEP) from phenylketonuric humans, while systematically manipulating rates of amine synthesis in the central nervous system using two techniques. We have observed that stimulation of monoaminergic activity in the visual processing system, either by lowering inhibitory levels of phenylalanine through dietary restriction or by a properly balanced administration of indole and catecholamine precursors, shortened VEP latencies and permitted the development of a discriminative brain response to patterned stimuli. The close temporal relationship between these electrophysiological changes and the neurochemical manipulations following treatment initiation of discontinuation argue that monoamines play a significant role in the mediation of human sensory evoked potentials.

The effects of subacute and chronic exposure to 4-aminopyridine on reproduction in coturnix quail.

When male and female coturnix quail (Coturnix coturnix) were given a single subacute oral dose (5.62 mg/kg) of the avian frightening agent 4-aminopyridine (4AP) and paired with untreated mates, there was no effect on the reproductive performance of males; egg production of females was reduced the third week after treatment but recovered during the fourth week. Chronic exposure to 31.6, 100, and 316 ppm of 4AP in the diet of mated pairs did not affect reproductive performance during or after the 4- or 6-week period the chemical was fed, but no birds fed 1,000 ppm produced live chicks after treatment began and all died within 3 weeks. The 28-day LC50 of 4AP was determined to be 447 ppm for male coturnix and 562 ppm for females. F1 progeny from quail fed 31.6, 100, and 316 ppm 4AP and randomly mated at maturity showed no reproductive effects from their parents' exposure.

Self-stimulation alters human sensory brain responses.

Human electrocortical potentials evoked by self-administered auditory and visual stimuli manifest much smaller amplitude and faster poststimulus timing than do average brain responses evoked by identical machine-delivered stimuli. Auditory evoked potentials show this "self-stimulation effect" to a greater degree than do visual responses. For visual evoked potentials, the effect appears greater at the vertex association area than over the occipital cortex. Individual differences in the magnitude of the "self-stimutlation effect" relate to level of intelligence.