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PubMed1987

Associatively reduced withdrawal from shadows in Hermissenda: a direct behavioral analog of photoreceptor responses to brief light steps.

When the nudibranch Hermissenda crassicornis encounters a shadow in an otherwise uniformly illuminated field, it stops and turns back into the light within seconds. Associative conditioning, with paired light and rotation stimuli, produces learned modifications of phototaxis in illumination gradients. This same training procedure significantly reduced the ability of paired, but not random or naive control animals, to withdraw from shadows. In naive animals, after 13 min of dark adaptation, withdrawal from shadows was less apparent when animals encountered this stimulus the first time than after the second encounter. This difference in responsiveness to the first and second edge stimulus paralleled differences in type B photoreceptor impulse frequencies recorded during and after first and second steps of light. Earlier studies have shown that associative training of Hermissenda increases a long-lasting depolarization (LLD) which follows a light step. Our present findings suggest a functional relationship between the LLD of the type B photoreceptor and the behavioral response to light-dark differences. This supports the view that membrane changes which cause modifications of LLD magnitude store the learned association for later recall.

Animals↗
PubMed1987

Training and testing determinants of short-term associative suppression of phototaxic behavior in Hermissenda.

Hermissenda crassicornis shows both short- and long-term retention of conditioning following light-rotation pairings. Previous research has shown that prolonged training (50 trials per session, three consecutive daily sessions) produces a suppression of phototaxis lasting for days. This long-term retention reflects associative learning processes, with little or no contribution of nonassociative learning. In contrast, both associative learning and nonassociative behavioral modification contribute to short-term retention following a single session of five pairing trials. In this paper, we describe important associative and nonassociative determinants of short-term changes in phototaxis. In Experiment 1, animals received successive hourly tests for phototaxis in either a horizontal or a vertical orientation. Repeated testing resulted in decreased phototaxis which was especially pronounced for animals tested horizontally. Experiments 2-4 demonstrated that both repeated handling of animals and repeated periods of dark adaptation prior to each phototaxic test contributed to the development of phototaxic suppression with repeated testing. These nonassociative influences on phototaxis interacted with the gravitational orientation employed during behavioral testing, being most pronounced for testing in the horizontal orientation. An implication of these findings is that attempts to demonstrate short-term pairing-specific suppression will be most successful when nonassociative contributions are minimized (by testing animals vertically). Experiment 5 tested this prediction. We also tested the influence of training light intensity and the stimulus specificity of conditioned suppression. Animals received either five paired or five random presentations of light and rotation. Training light intensity was either moderate or bright. Following training, animals were tested for either suppression of phototaxis or suppression of negative geotaxis, using either a horizontal or a vertical testing orientation. Consistent with previous results, horizontally tested animals exhibited pronounced nonassociative suppression following training. The use of a bright training light also produced nonassociative suppression. However, when trained with a light of moderate intensity and tested vertically, Hermissenda showed associative suppression of phototaxis (significant paired--random difference) but not geotaxis (no paired--random difference). In a final experiment we observed that the longer the period of dark adaptation (prior to testing) the longer the phototaxic latency.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Discriminative conditioning alters food preferences in the leech, Haemopis marmorata.

The feeding behavior of the carnivorous leech, Haemopis marmorata, was aversively trained in a discriminative classical conditioning task. Two conditioned stimuli were used: One consisted of a food (chicken or liver) paired with an unconditioned stimulus of quinidine (bitter chemical); the other consisted of the alternate food presented in an unpaired relationship with the quinidine. Training consisted of alternating exposures to the two conditioned stimuli. Testing consisted of the simultaneous presentation of a conditioned stimulus food and a neutral food, beef. The percentages of responding to the conditioned stimuli were tabulated. Haemopis could discriminate between the conditioned stimuli. As a result of pairing a food with quinidine, the leeches selectively reduced their preference for that paired food, while they did not alter their preference for the unpaired food.

Animals↗
PubMed1988

Salience and the effects of CS preexposure on aversion conditioning.

Rats (n = 84) received preexposure to distilled water or to one of two differently salient flavors, 5.0% casein or 10.0% sucrose, casein being the more salient. Each preexposure group then received aversion conditioning to a 5.0% casein or a 10.0% sucrose CS. Aversion effects were reliably more enduring to casein than to sucrose. Relative to water-preexposed groups, preexposure to casein attenuated aversion effects to the casein CS reliably less than preexposure to sucrose attenuated aversion effects to the sucrose CS. During preexposure, neophobia was reliably greater to casein than to sucrose, suggesting that the demonstration of salience in taste aversion learning may be based on the inherent aversive properties of novelty.

Animals↗
PubMed1989

Early (preweanling) recognition of alcohol's orosensory cues resulting from acute ethanol intoxication.

Three experiments were conducted in order to analyze the possibility that during acute alcohol intoxication, preweanling rats process ethanol's orosensory cues. Intragastric administration of an ethanol dose equivalent to 3.0 g/kg resulted in peak blood alcohol levels greater than 250 mg% (Experiment 1). Twenty-four hours after receiving this dose, 11-day-old pups expressed an ethanol odor aversion in a locational test. This aversion response was not observed when pups were previously administered an ethanol dose resulting in blood alcohol levels lower than 150 mg% (Experiment 2). Nevertheless when subjects received such a lower dose and 30 to 60 min after administration suffered nociceptive stimulation, alcohol aversions were also detected in terms of alcohol ingestion patterns and ethanol odor aversions (Experiment 3). These results appear to indicate that orosensory ethanol processing takes place during acute ethanol intoxication probably due to ethanol elimination via respiration, salivation, and/or hematogenic olfaction processes.

Alcoholic Intoxication↗
PubMed1989

Acute alcohol intoxication paired with appetitive reinforcement: effects upon ethanol intake in infant rats.

A recent study suggested that infant rats process alcohol odor and/or taste during acute ethanol intoxication probably due to ethanol elimination via respiration and salivation. The present set of experiments was meant to analyze the possibility that this orosensory processing may act as a conditioned stimulus when an appetitive reinforcer is paired with the state of intoxication. In the first experiment it was observed that intragastric administration of a mildly intoxicating ethanol dose (1.5 g/kg), paired during postabsorptive time intervals with oral infusion of sucrose, was sufficient to promote a significant preference to ethanol. In Experiment 2 different doses of ethanol were either paired or explicitly unpaired with sucrose administration. The result reported in Experiment 1 was replicated and it was observed that a higher dose (3.0 g/kg) unpaired with the reinforcer resulted in alcohol aversions in terms of alcohol consumption patterns. However, when the reinforcer was paired with this dose, the aversion was inhibited. Finally, in the third experiment results indicated that preexposure to alcohol odor eliminates sucrose-conditioned alcohol preferences. These results indicate that, in physiologically immature rats, alcohol preference can be regulated by prior associative experiences involving the state of intoxication and consequences internal and/or inherent to this state.

Alcohol Drinking↗
PubMed1999

Norepinephrine and associative conditioning in the neonatal rat somatosensory system.

Neonatal rats, aged postnatal days 3-4, were trained in a somatosensory associative conditioning task involving temporal correlation of facial vibrissa stimulation and aversive shock. This training resulted in a subsequent conditioned behavioral activation/arousal response to vibrissa stimulation alone, compared to non-learning control pups trained with random vibrissa-shock presentations. The acquisition of the conditioned response was blocked by systemic injections of the NE beta-receptor antagonist propranolol in a dose-dependent manner. In a second study, vibrissa stimulation was paired with systemic injections of the NE beta-receptor agonist isoproterenol. Association of vibrissa stimulation with beta-receptor activation resulted in subsequent conditioned responses to vibrissa stimulation alone, in a dose-dependent manner. Together, these results suggest that early associative somatosensory conditioning requires and involves NE in a manner similar to that previously demonstrated for early olfactory learning.

Adrenergic beta-Agonists↗
PubMed2000

Spatial ability of XY sex-reversed female mice.

Perinatal gonadal hormones significantly affect subsequent sex differences in reproductive and non-reproductive behaviors in rodents. However, the influence of the sex chromosomes on these behaviors has been largely ignored. To assess the influence of the non-pseudoautosomal region of the Y chromosome, C57BL/JEi male and female mice and mice from the C57BL/6JEi-Y(POS) consomic strain were given behavioral tests known to distinguish males from females. The C57BL/6JEi-Y(POS) strain contains sex-reversed XY-females which, when compared to their XX-female siblings, allow assessment of the influence of the Y chromosome in a female phenotype. XX-females and XY-females did not differ on open-field activity, the Lashley maze, or active avoidance learning, but XY-females were significantly better than XX-females on the Morris hidden platform spatial maze. These findings suggest that males may have both a genetic and a hormonal mechanism to ensure visuospatial superiority.

Animals↗