Role of ingestion in odor-toxicosis learning in the rat.

Conducted 2 experiments with 32 and 34 male Charles River albino rats, in which Ss evidenced aversions to an odor paired with toxicosis in both drinking and exploratory behavior tests. Ingestion during odor-toxicosis conditioning in Exp I resulted in stronger aversions only in tests involving drinking the same solution as had been ingested during training, despite the absence of enhanced aversions to the flavor of the solution used. This result is interpreted as evidence that Ss drinking during conditioning acquired aversions not only to the CS odor but also to additional cues arising from an interaction of the CS odor and the flavor of the ingested solution. Exp II showed that these interaction cues were not the result of a flavor imparted to the ingested substance by dissolved molecules of the odorizing agent. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compound conditioning in honeybees.

In Exp I, 42 free-flying honeybees were extinguished in choice tests after reinforcement for response to distinctively colored and scented targets. In Exp II (8 Ss), an overshadowing experiment of conventional 2?×?2 design, color was overshadowed by odor, but odor was potentiated by color. Results are interpreted in terms of compound uniqueness and within-compound association, both of which were demonstrated in subsequent experiments with 28 Ss. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flavor-illness aversions: Gustatory neocortex ablations disrupt taste but not taste-potentiated odor cues.

Two studies evaluated the contribution of the gustatory neocortex (GN) to the potentiation of odor by taste during illness-induced aversions in 130 male Sprague-Dawley rats. In Exp I, Ss lacking GN and controls were given an odor, a taste, or an odor–taste compound cue followed by intragastric gavage of LiCl. Prior to conditioning, neophobia for flavored solutions was absent in Ss with GN lesions. After pairing with LiCl, GN Ss developed normal conditioned odor aversions, whereas conditioned taste aversions were attenuated or totally blocked. Potentiation of odor by taste after compound conditioning was evident in both control and GN Ss. In Exp II, normal Ss were given compound conditioning to induce potentiated odor aversions and then given GN lesions prior to tests with the odor and taste components. Taste aversion retention was totally disrupted by GN ablation; potentiated odor aversions were retained by both groups, although the GN group extinguished faster. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory stimulation induces filial preferences for huddling in rat pups.

Rat pups of all ages huddle with conspecifics, but the sensory control of contact behavior changes ontogenetically. Thermal cues control huddling until about Day 15, at which time species' odors become the dominant stimulus. The present 2 experiments with 150 Sprague-Dawley rat pups indicate that the filial response to conspecifics is dependent on olfactory experience. A synthetic chemical scent was added to the smells of the dam from Day 1 to Day 20 postpartum. Standardized videographic tests were used to assess the development of huddling preference. Preferences for nest-typical smells emerged by Day 15 in Ss from both scented and nonscented litters. Ss from scented nests preferred to huddle with a scented stimulus rat, whereas control Ss preferred a nonadulterated rat stimulus. Additional testing indicated that the affirmative preferences were specific to rearing odor and were not based on decreased aversion to test scents or on disrupted olfactory discrimination. The ontogeny of species-typical contact behavior is discussed in terms of the induction of a perceptual preference that is based on early odor stimulation. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Respondent conditioning of self-injurious behavior in early socially deprived rhesus monkeys (Macaca mulatta).

Examined whether certain environmental events could elicit self-injurious behavior (SIB) and whether the resulting SIB could be conditioned to an antecedently presented external stimulus. Exp I showed that SIB could be elicited in 4 socially isolated rhesus monkeys by the application of brief, mild, electric footshock. In Exp II, 3 socially isolated Ss were exposed to a procedure that paired a 10-sec tone with a 1-sec electric footshock. Three control Ss received presentations of the tone alone. Results show that Ss in the experimental group began to show SIB during the tone periods, thereby providing evidence of respondent conditioning. Data expand the scope of the learning model of SIB from primarily operant interpretations to respondent conditioning as well. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste potentiation of poisoned odor by temporal contiguity.

Investigated the synergistic interaction between odor and taste in flavor-toxicosis conditioning in 2 experiments with 85 male Sprague-Dawley rats, in which the temporal interval between a 2-min odor and a 2-min taste was varied for thirsty Ss licking at a water spout. In Exp I (34 Ss), taste was presented at 0 min, and odor was presented at –20, –2, 0, 1, and 10 min to independent groups in a simple compartment. In Exp II (51 Ss), taste was presented at 0 min, and odor was presented at –5, –2, and 0 min in a wind-tunnel apparatus. Results indicate that odor alone was an ineffective CS for a toxic UCS under the conditions of the present experiments. Simultaneous (0-min) presentation of odor with taste potentiated the odor component so that it became more effective than the taste component. A 2-min interval between odor and taste attenuated potentiation, and a 5-min interval disrupted the effect. The interaction was asymmetrical; odor had no systematic effect on the conditioning of taste. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual conditioning and the control of copulatory behavior by species-specific sign stimuli in male Japanese quail.

Three experiments were conducted to identify species-specific sign stimuli sufficient to elicit copulatory behavior in male Japanese quail and to determine how learning is involved in the control of behavior by these sign stimuli. In Exp 1, sexually experienced Ss were tested for copulatory behavior with a live female quail and with a model consisting of a female quail's head and neck mounted in front of a foam pad. Comparable levels of copulatory behavior were observed in the two tests, indicating that static visual cues provided by a female quail's head and neck are sufficient to elicit copulatory behavior in this species. Exp 2 showed that male birds that previously received numerous opportunities to copulate with a live female quail in the test situation were significantly more likely to copulate with the head?+?neck model than were sexually inexperienced Ss. Exp 3 showed that prior sexual experience with live quail facilitated responding to the head?+?neck model only if the sexual experience was provided in the same place where Ss were later tested with the model. This finding suggests that sexual experience facilitates control of copulatory behavior by species-specific sign stimuli through contextual conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Representation-mediated overshadowing and potentiation of conditioned aversions.

Examined the ability of CS-evoked representations of flavored substances to modulate the conditioning of LiCl-based aversions to simultaneously presented flavors or odors. In Exps I–III, 156 thirsty Sprague-Dawley rats first received pairings of an auditory CS with a flavored-water UCS; they then received pairings of a compound stimulus with a toxin. Exp IV examined the potentiation of aversion conditioning to a novel odor using 32 Ss. In Exp I, conditioning of a flavor was partially overshadowed when it was presented in compound with a tone that had been previously paired with another flavor. Exp II replicated that result and also found that conditioning to a flavor was not overshadowed when the flavor was presented in compound with a tone that had been paired with that same flavored substance. In Exps III and IV, conditioning to an odor stimulus was potentiated when it was presented in compound with either a tone or another odor that had been previously paired with a flavor stimulus. Results suggest that evoked representations of stimuli may substitute for those events themselves in a variety of associative functions. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age of first appearance of simultaneous and successive negative contrast in infant rats.

Simultaneous (SimNC) and successive (SNC) negative contrast, 2 paradoxical effects that are related to shifts in reward magnitude, were studied in 148 rat pups. In Exps I and II, 11-, 14-, and 17-day-old Ss were able to discriminate between the large (milk suckling) and small (dry suckling) reward odor cues as measured by attachment latencies, but only the 14- and 17-day-olds showed SimNC. At none of the 3 ages was a discrimination formed to the differential odor cues in the alley in terms of runway speeds. In Exp III, Ss were placed directly on the dam's ventrum to facilitate attachment. As in the earlier experiment, the 11-day-olds discriminated between the odors signaling the 2 reward conditions but did not show the SimNC effect. In Exp IV, SNC was shown at 17 days but not at 14 days in the attachment latency measure and at neither age in the run measure. These 4 experiments extend earlier findings that the paradoxical effects that emerge out of intermittent schedules of reward magnitude occur earlier than those associated with single abrupt shifts in reward magnitude. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intermale fighting affected by home-cage odors of male and female mice.

Conducted 3 experiments to test the hypothesis that male mice can produce an aggression-inhibitory or facilitory odor under varying conditions of social stimulation. In Exp I, 25 male fighter mice fought 25 castrated opponents more vigorously in soiled home cages of either single or stable groups of male mice than they did in clean cages. Fighting was also stimulated in cages briefly occupied by other pairs of fighting mice. It is concluded that the release of aggression-promoting home-cage odors by male mice is not necessarily a consequence of social instability and that they are of urinary, rather than preputial, origin. In Exp II (with 21 fresh Ss) and Exp. III (with 30 Ss from Exp I), odors deposited by either single or groups of female mice greatly reduced fighting, indicating that their urinary aggression-inhibiting pheromone is effective after deposition upon the home environment. Testosterone propionate implants abolished the females' inhibitory pheromone and did so independently of their enlarged preputial glands. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Daily biorhythmicity influences homing behavior, psychopharmacological responsiveness, learning, and retention of suckling rats.

385 Sprague-Dawley suckling rats were used to investigate the effects of 24-hr biorhythmicity on performance. Nest-seeking (homing) in 7-day-old Ss and its facilitation by dextro-amphetamine varied across time of day. Analysis of initial choice revealed that Ss' ability to detect and position themselves in the direction of the nest did not vary across time of day. Homing behavior was not an artifact of random activity level but was related to Ss' motor performance, which varied with a daily rhythm. Circadian rhythmic influences on acquisition and retention of an amphetamine-induced odor aversion were demonstrated by manipulating time of day of conditioning and subsequent retention testing. The time of day effect on conditioning was attributed, in part, to daily rhythmic changes in the effectiveness of the UCS. Retention was optimal in Ss tested at the time of day corresponding to that of their original training. Thus, time of day may serve as an important contextual stimulus for retention in immature as well as adult Ss. (101 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical motor neuron activity in the cat during classical conditioning with central stimulation as the CS and the US.

Studied the neuronal basis of associative conditioning in the cat by pairing stimulation of thalamocortical pathways as the CS with antidromic activation of pericruciate pyramidal tract (PT) cells as the UCS in a differential classical conditioning paradigm. For the 18 Ss in Exp I, the target thalamic nuclei for stimulation were nucleus ventralis posterolateralis (VPL) and nucleus ventralis lateralis. For the 10 Ss in Exp II, the target thalamic nuclei were VPL and nucleus cetromedian. Results show that thalamic stimulation was not an effective CS. The response of PT cells to thalamic stimulation did not change as a function of reinforcement with PT stimulation. These results do not support the hypothesis that the simple pairing of any 2 neural events is the essential mechanism underlying associative conditioning changes. Instead, they suggest that the combined activation of specific and nonspecific thalamic nuclei may be important in producing increases in responsiveness of PT neurons. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive significance of the copulatory behavior pattern of male meadow voles (Microtus pennsylvanicus) in relation to induction of ovulation and implantation in females.

Investigated the adaptive significance of 2 attributes of the male vole copulatory behavior pattern, its elaborateness, and distinct temporal patterning in relation to the induction of ovulation and implantation in females. In Exp I (58 Ss) elaborateness of the male behavior pattern, as evidenced by extensive preejaculatory behavior and multiple ejaculatory series, was necessary for maximal ovulation and implantation in meadow vole females, especially older females. In Exp II, 16 male meadow voles were able to elicit ovulation and luteal activation in 51 females of 2 other Microtus species, even though the temporal patterning of male meadow vole behavior was completely different from the patterning of the females' conspecific males (20 Ss). Implantation did not occur apparently because of incomplete ova development. It is suggested that in Microtus a coadaptation exists between male behavior pattern and female stimulation requirements with respect to amount of stimulation but not to the specific temporal patterning of the stimulation. It is unlikely, therefore, that the different patterns of male copulatory behavior in Microtus would be effective in maintaining reproductive isolation among sympatric species. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual approach conditioning: Tests of unconditioned stimulus devaluation using hormone manipulations.

Contents of learning that result from CS–unconditioned stimulus/stimuli (UCS) pairings in sexual approach conditioning were explored with male Japanese quail (Coturnix coturnix japonica). Sexual motivation of Ss conditioned to approach an arbitrary stimulus in a Pavlovian sexual conditioning paradigm was reduced by exposing them to a short photoperiod. Decreased sexual motivation resulted in a decline in sexually conditioned approach behavior (Exps 1 and 2). Responding was restored when Ss were returned to a long photoperiod (Exp 1) and when exogenous testosterone was administered (Exp 2). Decreased sexual motivation did not affect food-conditioned approach behavior (Exp 3). These results suggest that sexually conditioned approach behavior is mediated by a representation of the UCS, which is activated by the CS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unconditioned stress-induced analgesia following exposure to brief footshock.

Four experiments, with 136 male Sprague-Dawley rats, examined the properties of unconditioned analgesia elicited by electric footshock stimuli using UCS parameters typical of aversive conditioning paradigms. In all experiments, analgesia was inferred from the latency to paw lick in response to painful thermal stimulation in the hot-plate assay. In Exp I, Ss exposed to a 1-sec, 2-mA shock UCS showed significantly longer latencies to respond to painful thermal stimulation than nonshocked controls, whereas nonsignificant increases in response latencies were observed with 1-sec shock UCS of either 0.5 or 1.25 mA. In Exp II, Ss exposed to a 2-mA electric shock UCS showed systematic increases in latencies to respond to painful thermal stimulation as the duration of the shock was varied between 0.5 and 2 sec. Exp III showed that this form of shock-induced analgesia was of short temporal duration. Specifically, significant increases in latencies to respond to painful thermal stimulation occurred 30 but not 90 or 300 sec following exposure to shock. Exp IV demonstrated that this form of analgesia was unaffected by pretreatment with the opiate receptor antagonist naloxone HCl in ip dosages of 1, 5, 10, or 20 mg/kg. Finally, there was no evidence showing that environmental stimuli paired with shock presentations acquired the capacity to evoke analgesia as a conditioned response. Implications of shock-induced analgesia for the study of aversive conditioning and behavior are discussed. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dehydration inhibits suckling behavior in weanling rats.

Determined the relation between dehydration and suckling behavior in 567 Sprague-Dawley weanling rats 15, 20, and 23 days of age. After 15 days of age, intra- and extracellular dehydration sharply reduced both the number of Ss that suckled and the amount of milk consumed. Rehydration returned both behaviors to control levels. Thus, during the weaning period, the internal determinants of suckling are not homologous with those of drinking, but are more homologous with those governing feeding. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behaviorally functional opioid systems in infant rats: I. Evidence for olfactory and gustatory classical conditioning.

Conducted 2 series of experiments to characterize the behavioral function of opioid systems in neonatal rats. In the 1st series, the reinforcing properties of exogenous opioids were investigated in 112 5-day-old pups. Ss' ability to associate the novel taste of saccharin, received while suckling, with intraperitoneal morphine injections was assessed. Results show that Ss that received 0.5 ml of saccharin prior to morphine administration ingested considerably more saccharin on Day 10 than did control rats. The 2nd set of experiments was conducted to determine whether 144 rat pups could associate a novel odor with morphine administration. Five days after conditioning, that stimulus was highly preferred by morphine-treated Ss compared with saline control Ss. Thus positive associations were formed with either a novel taste stimulus experienced while suckling or with an odor experienced during social isolation. Conditioning was cue specific and was retained for at least 5 days. The formation of these associations was blocked with opioid antagonists given prior to conditioning. Data suggest behaviorally functional opioid receptors and raise the possibility of a functional role of the endogenous opioids in motivational processes in infant rats. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Augmentation of taste conditioning by a preconditioned odor.

Five experiments explored facilitated taste-aversion conditioning (odor-mediated taste augmentation), using rats that experienced odor (A) and taste (X) in an A+/AX+ design. Augmentation occurred when the stimuli were presented simultaneously during AX+ conditioning, and significantly weaker conditioning occurred after a sequential presentation (Exp 1). Exps 2 and 3 demonstrated that augmented conditioning decreased if the odor aversion was reduced through preexposure or extinction following A+ conditioning. A second-order conditioning explanation was not supported by the results of Exp 4. Exp 5 showed that extinction of the odor aversion after AX + conditioning did not alter the strength of the augmented taste aversion. Odor-mediated taste augmentation is similar to potentiation, in which odor and taste cues operate in a synergistic, not competitive, manner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental study of unconscious influences: Ultrasound as a stimulus.

Used ultrasound as a stimulus to study its effects on behavior without S awareness. In Exp I evoked responses were elicited in 7 of 24 undergraduates by ultrasonic tones when Ss were reporting the presence of no stimulus. In Exp II with 20 male Ss, galvanic skin response conditioning to a compound stimulus made up of ultrasound and a red light resulted in shorter latencies to the compound stimulus than to the red light alone, during extinction. The differences did not appear among control Ss, supporting the occurrence of conditioning without awareness. In Exp III with 16 Ss, reaction-time performance was disrupted by providing ultrasound as an anticipatory cue for 1 of 2 lights over 150 trials and then reversing the ultrasound-light pairing. The ultrasound did not facilitate reaction time to the paired light during the 1st 150 trials, however. Results support learning without awareness, and the method is discussed as it might be extended to the study of unconscious influences and to clinical applications. (75 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Isolation-induced aggression in newly hatched ducklings.

Describes 3 experiments with a total of 40 Khaki Campbell ducklings. In Exp I newly hatched Ss were initially housed in pairs and subsequently transferred to isolated housing conditions. Ss living with another bird displayed filial behavior and little aggression upon encountering another duckling in a test arena. In contrast, Ss housed in isolation exhibited aggressive pecking in addition to filial behavior when another duckling was subsequently encountered. In Exp II, Ss were housed with an imprinting object (i.e., an object that elicits attachment behavior) but were otherwise isolated from other birds. These Ss displayed little aggression when they were subsequently reunited with a conspecific, indicating that the aggression-precluding effects of social housing are not limited to the particular social stimulus with which the ducklings are housed. In Exp III, Ss were again housed with an imprinting object, but this time the object was behind glass, thereby precluding tactile contact with it. Since these Ss also exhibited little aggression when reunited with a conspecific, it is apparent that visual stimulation from an imprinting object is sufficient in itself to preclude subsequent aggression. Findings suggest that stimulation that elicits attachment behavior is the critical factor mediating isolation-induced aggression. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)