Susan M. Nash

Extinguishing conditioned inhibition in flavour-aversion learning: effects of repeated testing and extinction of the excitatory element.

Three conditioned inhibition experiments using an A+/AX- design are reported in which lithium-mediated excitatory conditioning occurred to distinctive environmental stimuli and inhibitory conditioning to a vinegar flavour. Increased vinegar preferences were observed (i.e., conditioned inhibition) in each experiment, and these preferences extinguished with repeated testing as well as following extinction of the excitatory element. Vinegar preferences could be reinstated through reconditioning of the extinguished excitatory stimulus. These experiments speak to the status of inhibitory responding as a “slave” process to conditioned excitation.

Taste Preference of the Adult Rat as a Function of Prenatal Exposure to Ethanol

Two groups of pregnant rats (n = 10) received exposure to either 10% ethanol or water. All male offspring (n = 43) received a six-day preference test (ethanol vs water) at 90 days of age. Fluid consumption scores indicated a significant preference for water by all Ss. However, those animals receiving prenatal ethanol exposure consumed significantly more ethanol during preference testing than did the animals receiving prenatal water exposure.

Defensive Burying: The Effects of Multiple Stimulus Presentation and Extinction

Two groups of rats served in an evaluation of the effects of multiple aversive-stimulus presentations and extinction upon defensive burying responding. The results indicate that multiple shock presentations resulted in significantly more burying than did a single shock. A significant reduction in responding was shown by both groups by the second extinction session.

Learned helplessness in goldfish under conditions of low shock intensity.

Summary Goldfish which received inescapable shock presentations during a first experimental phase made significantly fewer responses and had significantly longer response latencies during a subsequent avoidance-learning phase than did Ss which had not received the inescapable shocks.

The Effects of Flavor-Aversion Learning on Instrumental Performance

Two experiments investigated the role of lithium-mediated environmental conditioning on instrumental performance. Experiment 1 demonstrated that a novel taste consumed in one arm of a T maze prior to lithium-induced toxicosis reduced performance in this environment whereas similar aversions conditioned in the home cage failed to alter maze performance. Experiment 2 showed that maze performance in a straight alleyway was decremented during extinction only in a group that actually traversed the alley prior to drinking saccharin and receiving lithium injections. This demonstrated that the instrumental decrement observed in Experiment 1 was due not only to the presence of an unpalatable flavor in the goalbox during the test.

Open-Field Foraging: The Influence of Prior Taste-Aversion Conditioning

Two experiments evaluating open-field foraging behavior of rats that had received prior taste aversion conditioning to liquid saccharin are reported. In both studies each rat had free access to six foraging patches containing powdered laboratory chow (three plain, three saccharin-adulterated). As consumption at the saccharin-adulterated patches was significantly less for taste-aversion treated animals than at the plain patches, generalization of a taste aversion to a different type of ingestive stimulus in a different environment was demonstrated. The possible relationship of these data to environmental potentiation effects is discussed.

Odor-Based Runway Performance of Rats as A Function of Type of Reinforcer and Multiple Deprivation Conditions

Two experiments examining the development of odor-based double-alternation patterning under concurrent food and water deprivation, but food versus water reinforcement, are reported. In both experiments patterning was established only by animals receiving food reinforcement. Shifting type of reinforcer (i.e., food to water, and vice versa) resulted in an immediate and pronounced change in performance (Experiment 1). Increasing the duration of water deprivation (Experiment 2) produced an increase in general performance level, but did not result in the development of patterning by water-reinforced animals. These results would appear to be supportive of an ethologically based interpretation, such as optimal foraging theory.

Prenatal exposure to aluminum or stress: I. Birth-related and developmental effects

Sperm-positive female rats in one of two experimental conditions either ingested aluminum hydroxide (via a Maalox-water mixture) or were stessed (via mild electric shock) during gestation. Birth-related effects, such as stillborn pups, aborted litters, and cannibalism, were found for the animals in the two experimental conditions, but not for the control animals. Significantly lower weights (through 70 days of age) were associated with aluminum-exposed offspring that had been maintained with a nursing mother that had recieved the Maalox-water mixture until weaning.

Prenatal exposure to aluminum or stress: II. Behavioral and performance effects

In this second report dealing with the effects of prenatal exposure to aluminum or stress, the results of shock-elicited aggression and learned helplessness testing are presented. When compared to controls, aluminum- and stress-exposed offspring displayed significantly more aggressive responses. However, aluminum-exposed offspring spent significantly less time per aggressive response in contact with the target rod. Moreover, aluminum-exposed animals had significantly longer latencies than did stress-exposed animals during the escape-training phase of the learned helplessness study. These results indicated that the prenatal treatments employed may eventuate in behavioral effects with one of these effects being the disruption of a response inhibition/direction mechanism in the aluminum-exposed animals.

Reward and nonreward odor cues: The role of the harderian gland

Through the comparison of the performance of a group of glandectomized rats with that of a group of sham-operated rats on a double-alternation schedule of reward-nonreward (R-N), the role of the harderian gland in the production and/or release of R and N odor cues was evaluated. The establishment of appropriate patterned responding by both harderianectomized and shamoperated animals argues against this gland’s being involved in the odor control of maze learning. Additional potential odor sources are considered.