Oddity performance in preschool children at risk for mental retardation: transfer and maintenance.

The oddity performance of five preschool children at risk for mental retardation was facilitated by increasing the number of nonodd elements in a visual array. A combination intrasubject reversal and multiple baseline across subjects design indicated the internal validity of interventions designed to enhance the perceptual salience and consequent stimulus control of the odd stimulus. Results demonstrate that transfer and maintenance of oddity learning can be obtained even with individuals for whom correct oddity responding is uncommon. The typically poor performance of young and developmentally delayed children as compared to nondelayed children on tasks such as the oddity task may be attributable to a lower sensitivity to relational information.

Amphetamine-haloperidol discrimination: effects of chronic drug treatment.

Rats responding for food reinforcement were trained in a 2-lever drug discrimination task. Groups of rats were trained to discriminate one of four doses of amphetamine (0.0, 0.1, 0.3, or 0.5 mg/kg) from haloperidol (0.02 mg/kg). Both the rate of acquisition and level of discrimination at asymptote were a function of amphetamine training dose. Following acquisition of this discrimination, choice behavior was assessed in the absence of drug during two test sessions. Twenty-four hours following the second drug-free test session, chronic drug treatment commenced. Half of the animals received 10 mg/kg amphetamine for 10 consecutive days while the other half received 1 mg/kg haloperidol during the same period. Choice behavior was assessed during three 2.5-minute unreinforced drug-free test sessions 24, 48, and 72 hours following the chronic drug regimen. Following chronic haloperidol, animals responded as though a small dose of amphetamine had been administered, while following chronic amphetamine, they responded as though a small dose of haloperidol had been administered. Collectively, these results suggest that animals trained to discriminate amphetamine from haloperidol respond on the basis of a continuum of dopaminergic function. Further, this continuum can be used to elucidate the net effect of pharmacologically-induced alterations in dopaminergic function, as well as the effect of nonpharmacological manipulations that may result in dopaminergic changes.

Discrimination of serotonergic drugs is unaltered in rats prenatally exposed to ethanol.

Pregnant rats were administered intragastrically 4.0 g/kg of ethanol (31.6% v/v) two times per diem on days 10-14 of gestation. A second group of pregnant rats were pair-fed to the ethanol treated group and placebo intubated, while a third group was not intubated. Prenatal ethanol exposure resulted in both reduced birth weight, weaning weight, and percent of pups surviving from birth to weaning. The treatment did not, however, affect the number of pups delivered. Two male pups approximately 60 days old were randomly selected from each litter for testing in a 2-lever drug discrimination task. One pup was trained to discriminate quipazine (3.0 mg/kg) from saline, while the second was trained to discriminate 5-HTP (30.0 mg/kg) + Ro4-4602, a peripheral decarboxylase inhibitor, from saline. Following acquisition, discrimination behavior was shown to be both dose and time dependent. None of these behavioral measures were altered by prenatal ethanol exposure.

Effects of prenatal alcohol on homing behavior, maternal responding and open-field activity in rats.

A radial-maze was used to study homing in offspring and maternal retrieval behaviors after prenatal exposure to alcohol. Pair-fed and untreated (ad lib control diet) groups were included and all offspring were either fostered or cross-fostered at birth. Offspring given ethanol prenatally exhibited a deficit in homing development and were retrieved significantly longer by ad lib control dams over the ten days of testing. The observed retrieval response may represent a compensation for the delayed development of the ethanol-exposed offspring. Consistent with our previous work, ethanol treatment had long-lasting effects on maternal body weight, offspring growth, and juvenile and adult activity as measured in the open-field. The findings suggest that these effects can be attributed to ethanol per se and not undernutrition or postnatal maternal influences. Further work aimed at identifying the stimulus properties underlying the complex maternal-infant interaction is needed in order to explain the observed differences in maternal retrieval response.