Hemostatic and fibrinolytic indices in neonatal foals with presumed septicemia

Gerbils learned to approach a spatial-olfactory stimulus that signaled access to their pairmate. Experiments 1 and 3 used a discrimination procedure in which 1 conditioned stimulus (the CS+) was presented immediately before access to the pairmate and another (the CS-) was presented alone. Both male and female gerbils came to approach the CS+ sooner than the CS- and spent more time near the CS+ than the CS-. Discrimination learning was facilitated by making the CS+ and CS- spatially distinct (Experiment 3). Learning also was demonstrated in male gerbils, using a between-subjects design with a single CS. Pairing the CS with the opportunity for social interaction resulted in greater approach to the CS within 10 trials than presenting the CS and social opportunity in an unpaired fashion (Experiment 2). These findings demonstrate social-affiliative learning in the Mongolian gerbil. Similarities and differences between these findings and sexual conditioning effects in other species are discussed.     

Learning and male–male sexual competition in Japanese quail (Coturnix japonica).

Male Japanese quail (Coturnix japonica) were trained individually to discriminate between 2 sounds presented at opposite ends of an outdoor aviary. One of the sounds (the positive conditioned stimulus [CS+]) was associated with the release of a female, and the other (the negative CS [CS–]) was presented alone. Which of the 2 sounds served as the CS+ (and which served as the CS–) was counterbalanced across Ss. The Ss came to approach their CS+ but did not move away from their CS–. After having been conditioned individually, the subjects were tested in pairs, with a single female released after the presentation of a stimulus that was the CS+ for one of the males and the CS– for the other male. During most of these tests, the male for whom the prefemale stimulus was the CS+ copulated with the female before the male for whom the prefemale stimulus was the CS–. These results indicate that learning can have an important role in competition for access to a reproductive partner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms of Pavlovian conditioning: Role of protection from habituation in spinal conditioning.

Conditioned antinociception can be established in spinal rats by pairing stimulation to one hind leg (the conditioned stimulus [CS]) with an intense tailshock (the unconditioned stimulus [US]). After this training, the paired CS (CS+) elicits greater antinociception on the tail-flick test than a CS that was explicitly unpaired (CS–). Five experiments are reported that suggest that this effect reflects protection from habituation. Experiment 1 showed that the CS (legshock) induces antinociception before training. Presenting the CS alone weakened (habituated) its antinociceptive impact (Experiment 2). Less habituation was observed when the CS was paired with the US (Experiment 3). Decreasing habituation to the CS– (by increasing the interval between trials) and facilitating habituation to the CS+ (by increasing the number of trials) effectively eliminated the CS+/CS– difference (Experiments 4 and 5). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Within-compound associations modulate the relative effectiveness of differential and Pavlovian conditioned inhibition procedures.

Four conditioned suppression experiments with 98 male albino rats compared the inhibitory strength of a Pavlovian conditioned inhibitory stimulus (CS–) and a differential CS– and identified some postconditioning manipulations that modulate the measured effectiveness of the CS–. In Exp I, more inhibition was detected to a differential inhibitor than to a Pavlovian inhibitor in summation and retardation tests. Exps II–IV provided evidence that some inhibition conditioned to the Pavlovian CS–, but not to the differential CS–, was masked by a within-compound association. In Exp II, postconditioning extinction presentations of the Pavlovian conditioned excitatory stimulus (CS+) increased the inhibition observed to its CS–. In Exp III, postconditioning pairings of the Pavlovian CS+ with a more powerful UCS than that used for conditioning reduced the inhibition observed to its CS–. In Exp IV, nonreinforced postconditioning presentations of the Pavlovian CS– increased the inhibition observed to that CS–. The unmasking and masking of inhibition conditioned to the Pavlovian CS– by operations that modulate the strength of the within-compound association also changed the relative effectiveness of the Pavlovian and differential procedures. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of contingency violations on the extinction of a conditioned fear inhibitor and a conditioned fear excitor.

In 4 experiments, 192 male Holtzman and Sprague-Dawley rats were used in a conditioned-suppression paradigm to assess the effects of contingency variations on responding to a conditioned stimulus (CS) inhibitor (CS–) and a conditioned stimulus excitor (CS+). In Exp I, various unconditioned stimulus/stimuli (UCS) frequencies were equated across the presence and absence of a CS– in the context of either background cues (continuous-trial procedure) or an explicit neutral event (discrete-trial procedure). With both procedures, a CS-alone treatment enhanced inhibition, whereas treatments involving 50 or 100% reinforcement for the CS– eliminated inhibition without conditioning excitation to that CS. The latter outcome also occurred in Exp II, with discrete-trial training equating considerably reduced UCS frequencies for the presence and absence of the CS–. In further evidence that inhibition was eliminated without conditioning excitation to the CS–, Exp III showed that a novel CS did not acquire excitation when 25, 50, or 100% reinforcement was equated across the presence and absence of that CS in the context of a discrete-trial event. Using the procedures of Exp I, Exp IV showed that a CS+ was extinguished by a CS-alone treatment but was substantially maintained by treatments involving 50 or 100% uncorrelated reinforcement. These effects for a CS+ and a CS– implicate CS–UCS contiguity, rather than contingency, as the factor determining the extinction of a CS. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal activity during classical discrimination—Reversal eyeblink conditioning in rabbits.

Multiple-unit neuronal recordings were taken from the hippocampi of 10 male, New Zealand white rabbits during classical discrimination and reversal eyeblink conditioning using 2 tones as the conditioned stimuli (CS+ and CS–) and an air-puff unconditioned stimulus. During discrimination training, characteristic learning-related activity was seen in the hippocampus on trials when a conditioned response (CR) was executed. During early phases of reversal training, however, when high numbers of CRs were evident to both the new CS+ (the former CS–) and the new CS– (the former CS+), no learning-related activity was observed. Characteristic CR-related hippocampal activity to the CS+ was observed only after the rabbits began to learn the reversal response. These results suggest that the hippocampus may encode different features of eyeblink conditioning during discrimination and reversal learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition as a "slave" process: Deactivation of conditioned inhibition through extinction of conditioned excitation.

In 4 experiments with 176 male albino Sprague-Dawley rats, a conditioned-suppression paradigm was used to investigate why a conditioned inhibition (CS–) does not extinguish when presented alone. Exp I assessed the role of blocking by excitatory contextual cues and/or an evoked representation of the conditioned excitor (CS+), which had been nonreinforced in conjunction with the CS–. When the CS+ and context were extinguished prior to presentations of the CS– alone, the CS– showed a retardation effect, reflecting latent inhibition, because no inhibition was detected in controls for which presentation of the CS– alone had been omitted. Exp II showed that the loss of conditioned inhibition (CI) was due to excitatory extinction and not to time since conditioning. When excitation was reconditioned to the extinguished CS+ (Exp I) or to a novel CS in the same context (Exp II), CI was restored. Exps III and IV evaluated whether the maintenance of CI depended on excitation that was generic in form or associatively tied to the training context. Results indicate no loss of CI when groups received CS+ extinction in that context, with concomitant presentations in a different context of the UCS by itself, for a novel CS, or correlated either positively or negatively with the original CS+. Overall findings suggest that CI is dependent on excitation: When excitation is extinguished, CI is deactivated; when excitation is reconditioned to the original or a new CS+ in the same or a different context, CI is restored. (41 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Dissociable effects of cingulate and medial frontal cortex lesions on stimulus-reward learning using a novel Pavlovian autoshaping procedure for the rat: Implications for the neurobiology of emotion.

The effects of quinolinic acid-induced lesions of the anterior cingulate, posterior cingulate, and medial frontal cortices on stimulus-reward learning were investigated with a novel Pavlovian autoshaping procedure in an apparatus allowing for the automated presentation of computer-graphic stimuli to rats (T. J. Bussey, J. L. Muir, & T. W. Robbins, 1994). White vertical rectangles were presented on the left or the right of a computer screen. One of these conditioned stimuli (the CS+) was always followed by the presentation of a sucrose pellet; the other, the CS–, was never followed by reward. With training, rats came to approach the CS+ more often than the CS–. Anterior cingulate cortex-lesioned rats failed to demonstrate normal discriminated approach, making significantly more approaches to the CS– than did sham-operated controls. Medial frontal cortex-lesioned rats acquired the task normally but had longer overall approach latencies. Posterior cingulate cortex lesions did not affect acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Topography of sexually conditioned behavior in male Japanese quail (Coturnix japonica) depends on the CS–US interval.

The interval between exposure to a CS to male quail and access to a female (the unconditioned stimulus [UCS]) was varied from 0.5 to 20 min using a Pavlovian delayed conditioning procedure. Increasing the CS–UCS interval altered the spatial distribution of sexual conditioned behavior. With a short CS–UCS interval (1 min), conditioning resulted in the Ss remaining close to the CS and increasing their locomotor behavior near the CS. With a long CS–UCS interval (20 min), the Ss approached the CS to some degree, but their locomotor behavior was increased in areas farther removed from the CS. Results are interpreted within the context of a behavior systems approach to the study of learning and indicate that the typical finding of an inverse relation between conditioned responding and the CS–UCS interval may be an artifact of the use of a limited range or behavioral measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned social aversion in the male Mongolian gerbil (Meriones unguiculatus).

Adult male Mongolian gerbils formed conditioned social aversions to young male conspecifics. The basic paradigm consisted of pairing an S with a young animal (test stimulus) for 5 min and then injecting the S with LiCl to produce gastrointestinal distress. When retested 48 hrs later, the S avoided the test stimulus, as indicated by significantly decreased investigation time and approach frequency. Through a series of 5 experiments with 290 Ss on dose level, delay of toxin injection, and stimulus generalization, it was demonstrated that a dose of .03 ml/g of .15 M LiCl was effective, the toxin should be given within 15 min of the preliminary social pairing, the social aversion was specific to the particular first paired stimulus animal, and isolation between test sessions was necessary for an aversion to develop. This paradigm extends knowledge of the learned aversion process and demonstrates that this type of learning can be generalized to a social situation by gerbils. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pedunculopontine tegmental nucleus lesions impair stimulus–reward learning in autoshaping and conditioned reinforcement paradigms.

The role of the pedunculopontine tegmental nucleus (PPTg) in stimulus–reward learning was assessed by testing the effects of PPTg lesions on performance in visual autoshaping and conditioned reinforcement (CRf) paradigms. Rats with PPTg lesions were unable to learn an association between a conditioned stimulus (CS) and a primary reward in either paradigm. In the autoshaping experiment, PPTg-lesioned rats approached the CS+ and CS– with equal frequency, and the latencies to respond to the two stimuli did not differ. PPTg lesions also disrupted discriminated approaches to an appetitive CS in the CRf paradigm and completely abolished the acquisition of responding with CRf. These data are discussed in the context of possible cognitive function of the PPTg, particularly in terms of lesion-induced disruptions of attentional processes that are mediated by the thalamus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pavlovian conditioning of agonistic behavior in male threespine stickleback (Gasterosteus aculeatus)

The red coloration of male stickleback (Gasterosteus aculeatus) possesses signal value in male-male interactions. Therefore, it was predicted that males would learn to associate a red signal more readily than a green signal with a conspecific rival in a Pavlovian conditioning experiment. Males were presented red and green signal lights where one signal was always paired with presentation of a rival (excitatory conditioned stimulus, CS+) and one signal was never paired with presentation of a rival (nonreinforced stimulus, CS-). Males learned the task rapidly, showing conditioned approach and zigzag responses, but CS+ vs. CS- differentiation persisted, even after a prolonged extinction period. In addition, there were no differences in learning rates between fish trained to the red signal as the CS+ and fish trained to the green signal as the CS+. The results suggest that, although males may rapidly learn about rivals, they are not predisposed to associated red (over green) with the appearance of a rival under the conditions of this experiment. Because males must establish and maintain territories in order to nest and mate, learning about neighboring rivals may be an adaptive mechanism by which males more effectively defend their territories and thereby increase their reproductive fitness.     

Topography of spatially directed conditioned responding: Effects of context and trial duration.

Domesticated quail (Coturnix japonica) received a discrete conditioned stimulus (CS) at one end of the experimental chamber paired with the opportunity to copulate with a female quail (the unconditioned stimulus) in a goal box located 112 cm away. Approach to the CS (sign tracking) and approach to the goal area (goal tracking) were measured. The duration of exposure to the experimental context (C) was varied in Experiment 1, and the duration of the conditioning trials (T) was varied in Experiment 2 for independent groups, creating C/T ratios of 1.0, 1.5, 4.5, 45, and 180. Contrary to previous reports of a direct relation between the C/T ratio and conditioned responding, in the present experiments, a shift in the topography and stimulus control of conditioned behavior occurred. Low C/T ratios (1.0–4.5) produced goal tracking controlled by contextual cues, whereas high C/T ratios (45 and 180) produced sign tracking controlled by the discrete CS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pavlovian inhibitory conditioning and tolerance to pentobarbital-induced hypothermia in rats.

One group of rats (discrimination group) from an S pool of 96 male Sprague-Dawley rats received training in which, on alternate days, 1 conditioned stimulus (CS+) was associated with administration of 30 mg/kg pentobarbital (PBB), and a different CS (CS–) with saline. Controls received either exposure to both CSs but not the drug or to the drug but no CSs or to neither the CSs nor the drug. Subsequently, half the Ss in each group received injections of PBB in the presence of one of the CSs and the remaining half in the presence of the other CS. Results show that the discrimination group injected with PBB in the presence of CS+ displayed the most tolerance, whereas the discrimination group injected with PBB in the presence of CS– displayed the least tolerance. The attenuation of tolerance in the discrimination group injected in the presence of CS– provides evidence of inhibitory Pavlovian conditioning. Additional evidence of inhibitory conditioning was provided by the fact that CS? enhanced the hypothermic effects of PBB in the discrimination group, whereas CS? attenuated these effects. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Duration of signals for intertrial reinforcement and nonreinforcement in random control procedures.

In the random control procedure, responding to a conditioned stimulus (target CS) is prevented when the probability of unsignaled, unconditioned stimuli (UCS) in the intertrial interval (ITI) is equal to the probability of the UCS in the presence of the target CS. Three experiments used an autoshaping procedure with White Carneaux pigeons to examine the effects of the temporal duration of signals for the ITI UCS (cover CSs) and for concomitant periods of nonreinforcement. In Experiment 1, a short duration cover, but not a long duration cover, resulted in responding to the target CS. In Experiment 2, an explicit CS– cue during periods of nonreinforcement did not affect target acquisition. In Experiment 3, a long CS–, but not a short cover CS, was a sufficient condition for the acquisition of responding to the target CS. These results imply that the acquisition of responding to a target CS requires a discriminable period of nonreinforcement that is long relative to the target CS duration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Carbohydrate-conditioned odor preferences in rats.

The effectiveness of odor cues to support nutrient-conditioned flavor preferences in rats was studied. When the rats drank fluid, the CS+ odor was paired with intragastric (IG) infusions of Polycose, and the CS– odor with IG water. In Experiment 1, rats trained with almond and anise odors presented with plain drinking water failed to acquire a CS+ odor preference. In contrast, rats in Experiment 2 formed a strong aversion to anise (or almond) paired with lithium chloride, which indicated that the odors were distinguishable to the rats. Experiment 3 showed that providing unique tastes (bitter or sour) in combination with the odors during training potentiated odor conditioning. The rats displayed a strong preference for the odor?+?taste CS+ and for the odor component alone. Experiment 4 showed that with another pair of odors (peppermint and vanilla), CS+ preferences could be conditioned in the absence of taste cues during training. These results demonstrate that rats can acquire strong nutrient-conditioned odor preferences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Arousal-related associative response characteristics of dorsal lateral geniculate nucleus neurons during acoustic Pavlovian fear conditioning.

This research determined whether fear-conditioned, acoustic stimuli induce thalamic arousal reflected in associative responses in dorsal lateral geniculate nucleus (dLGN) neurons. Rabbits received a Pavlovian discriminative fear conditioning procedure in which one tone conditioned stimulus (CS+) was always paired with an aversive unconditioned stimulus (UCS) and another tone (CS–) was never paired with the UCS. Responses of single dLGN neurons to random CS+ and CS– presentations were then recorded. Nine of 15 recorded neurons demonstrated significantly greater firing during the CS+ versus the CS–. Their spontaneous activity demonstrated tonic firing during increased neocortical arousal and burst firing during decreased neocortical arousal. The results demonstrate that dLGN neurons show associative responses to fear-conditioned, acoustic stimuli and present a model for investigating the neural circuits by which such stimuli affect sensory processing at the thalamic level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in the sexual conditioned behavior of male and female Japanese quail (Coturnix japonica).

The conditioned responses of male and female Japanese quail (Coturnix japonica) were compared in a Pavlovian conditioning procedure in which presentation of a brief conditioned stimulus was immediately followed by the release of a copulation partner. Male quail vigorously approached the conditioned stimulus and were much more likely to enter the compartment housing their copulation partner than were female birds (Experiment 1). In females, sexual conditioning resulted in increased squatting (Experiment 2). This response was the reflection of sexual behavior rather than more general social behavior (Experiment 3). These findings provide the first definitive evidence of sexual learning in female quail and are consistent with the interpretation that sexual conditioning increases sexual arousal or receptivity in both sexes but the increase has different behavioral manifestations in male and female quail. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning of event sequences is based on response-effect learning: Further evidence from a serial reaction task.

Four experiments provide converging evidence that serial learning in a serial reaction task is based on response–effect learning, mediated by the learning of the relations between a response and the stimulus that follows it. In Experiment 1, the authors varied the stimulus sequence and the response–stimulus relations while holding the response sequence constant. Learning effects depended on the complexity of the response–stimulus relations but not on the stimulus–stimulus relations. In Experiment 2, transfer of serial learning from 1 stimulus sequence to another was only found when both sequences had identical response–stimulus relations. In Experiment 3, a variation of the stimulus sequence alone had no effect on serial learning, whereas in Experiment 4 learning effects increased when the response–stimulus relations but not the stimulus–stimulus relations were simplified. These findings suggest that serial learning is based on mechanisms of voluntary action control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)