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PubMed2005

beta2-Subunit-containing nicotinic acetylcholine receptors are involved in nicotine-induced increases in conditioned reinforcement but not progressive ratio responding for food in C57BL/6 mice.

RATIONALE: Nicotine administration potentiates conditioned reinforcement in rats, an effect that persists for weeks after chronic exposure. Little is known regarding the nicotinic receptor subtypes that may mediate this effect. OBJECTIVE: The purpose of this study was to determine whether beta2-subunit-containing nicotinic acetylcholine receptors (beta2*nAChRs) are necessary for lasting effects of nicotine on conditioned and primary reinforcement in mice. METHODS: Beta2 knockout (beta2KO) and wild-type (WT) mice received 14 days of nicotine exposure (NIC, 200 microg/ml in 2% saccharin) or saccharin alone (SAC) in their drinking water. Five days later, mice received paired presentations of a conditioned stimulus (CS) with water unconditioned stimulus (US) or explicitly unpaired presentations of the CS and US during Pavlovian discriminative approach training. Training was followed by two conditioned reinforcement tests. Mice were subsequently tested for food-reinforced responding in the absence of explicit cues followed by a progressive ratio test. RESULTS: During conditioned reinforcement testing, only mice in the paired condition showed increased responding in the CS-reinforced aperture over inactive apertures. WT-NIC mice showed enhanced conditioned reinforcement compared to WT-SAC animals. beta2KO-SAC mice showed elevated conditioned reinforcement compared to WT-SAC subjects, but beta2KO-NIC and beta2KO-SAC mice did not differ in responding with conditioned reinforcement. Prior nicotine exposure did not alter food-reinforced responding but resulted in elevated break points for food in both genotypes. CONCLUSION: These data show that nicotine exposure enhances conditioned reinforcement in mice and indicate that beta2*nAChRs are necessary for nicotine-dependent enhancement of incentive aspects of motivation but not motivation for primary reinforcement measured by progressive ratio responding.

Animals↗
PubMed1975

Stimulus input recruitment and stimulus trace decay factors in the trace conditioning deficit of severely retarded young adults.

Trace and delay classical eyelid conditioning procedures were used to investigate the relative contributions of conditioned stimulus input recruitment and trace decay processes to the trace conditioning deficit of severely and profoundly retarded subjects. The study included both trace and delay conditioning groups at interstimulus intervals of 500 and 950 msec. The conditioned stimulus durations were 50 msec for the 500-msec interstimulus interval trace group and 500 msec for the 950-msec interstimulus interval trace group. The "empty" interval between conditioned stimulus offset and the onset of the unconditioned stimulus was 450 msec for both trace conditioning groups. After 250 conditioning trials, there was no difference between the two trace groups, and both were significantly below the delay groups in final level of responding. These results suggest that stimulus trace decay rather than input recruitment, as manipulated by varying conditioned stimulus duration, accounts for the poor trace conditioning performance demonstrated by these subjects.

Adolescent↗
PubMed1983

Effects of scopolamine and methylscopolamine on classical conditioning of the rabbit nictitating membrane response.

Classical conditioning of the rabbit nictitating membrane response was accomplished by presenting tone- and light-conditioned stimuli for 800 msec before delivery of a 100-msec shock as the unconditioned stimulus. Scopolamine significantly retarded the rate of acquisition and final asymptotic performance of conditioned responses to the tone- and light-conditioned stimuli. Methylscopolamine was approximately 20 times less potent than scopolamine in retarding the rate of acquisition, and had no effect on the final asymptotic performance of conditioned responses. The retardation in acquisition of conditioned responses produced by scopolamine could still be detected 5 days after cessation of drug injections, indicating that the effects of scopolamine were on acquisition and not performance. In contrast, scopolamine and methylscopolamine had no affect on the development of long-term habituation produced by the unpaired presentations of tone, light and shock stimuli. Control experiments indicated that the acquisition of conditioned responses by animals injected with saline, scopolamine or methylscopolamine was not contaminated by the presence of changes in base-line responding, sensitization or pseudoconditioning. In addition, scopolamine and methylscopolamine did not affect the unconditioned nictitating membrane reflex. In previously trained animals, scopolamine produced a significant, approximately 25-db elevation in the intensity threshold of a tone-conditioned stimulus for elicitation of conditioned responses. It was concluded that scopolamine blocks the excitatory properties of tone stimuli and this accounts for its ability to retard the rate of acquisition of conditioned responses.

Acoustic Stimulation↗
PubMed2003

A twin study of the genetics of fear conditioning.

BACKGROUND: Fear conditioning is a traditional model for the acquisition of fears and phobias. Studies of the genetic architecture of fear conditioning may inform gene-finding strategies for anxiety disorders. The objective of this study was to determine the genetic and environmental sources of individual differences in fear conditioning by means of a twin sample. METHODS: Classic fear conditioning data were experimentally obtained from 173 same-sex twin pairs (90 monozygotic and 83 dizygotic). Sequences of evolutionary fear-relevant (snakes and spiders) and fear-irrelevant (circles and triangles) pictorial stimuli served as conditioned stimuli paired with a mild electric shock serving as the unconditioned stimulus. The outcome measure was the electrodermal skin conductance response. We applied structural equation modeling methods to the 3 conditioning phases of habituation, acquisition, and extinction to determine the extent to which genetic and environmental factors underlie individual variation in associative and nonassociative learning. RESULTS: All components of the fear conditioning process in humans demonstrated moderate heritability, in the range of 35% to 45%. Best-fitting multivariate models suggest that 2 sets of genes may underlie the trait of fear conditioning: one that most strongly affects nonassociative processes of habituation that also is shared with acquisition and extinction, and a second that appears related to associative fear conditioning processes. In addition, these data provide tentative evidence of differences in heritability based on the fear relevance of the stimuli. CONCLUSION: Genes represent a significant source of individual variation in the habituation, acquisition, and extinction of fears, and genetic effects specific to fear conditioning are involved.

Adult↗
PubMed2002

Post-training excitotoxic lesions of the dorsal hippocampus attenuate forward trace, backward trace, and delay fear conditioning in a temporally specific manner.

The present study sought to determine whether post-training excitotoxic lesions of the dorsal hippocampus would disrupt retention of fear conditioned using a trace procedure. Rats were trained using one of six procedures. Forward trace conditioning consisted of 10 trials in which a 16-s tone conditional stimulus (CS) was followed by a 28-s stimulus-free trace interval and then a mild footshock unconditional stimulus (US). We used two forms of delay conditioning where the tone and footshock co-terminated. Short delay used a 16-s tone and long delay used a 46-s tone. Backward trace conditioning was the same as forward trace, except that the order of the CS and US was reversed. CS-only and US-only were similar to forward trace except that the footshock or tone, respectively, was eliminated. One day later, animals received either an N-methyl-D-aspartate (NMDA)-induced lesion of the dorsal hippocampus or sham surgery. One week later, the rats were tested for freezing to the tone in a novel context. The next day, they were tested for freezing to the original training context. Hippocampal lesioned trace conditioned rats showed significantly less freezing during the tone compared with their sham lesioned controls. The lesion did not affect freezing during the tone in delay conditioning, nor in the other training conditions. During the 1-min period after tone offset, there was a trend in all hippocampal lesioned animals toward a deficit in freezing, compared with their corresponding sham lesioned controls, although only short delay, forward and backward trace groups showed a significant deficit. Hippocampal lesions also attenuated contextual conditioning. Thus, the hippocampus is critical for the consolidation and/or expression of a trace fear conditioned stimulus.

Animals↗
PubMed2003

Alcohol-induced memory impairment in trace fear conditioning: a hippocampus-specific effect.

It has been hypothesized that the amnesic effects of alcohol are through selective disruption of hippocampal function. Delay and trace fear conditioning are useful paradigms to investigate hippocampal-dependent and independent forms of memory. With delay fear conditioning, learning of explicit cues does not depend on normal hippocampal function, whereas learning explicit cues in trace fear conditioning does. In both delay and trace fear conditioning, the hippocampus is involved in learning to contextual cues, but it may not be entirely necessary. The present study investigates the effects of alcohol on the acquisition of delay and trace fear conditioning in mice, using freezing as a measure of learning. Male C57BL/6J mice were injected with 0.8 or 1.6 g/kg of 20% v/v alcohol and were immediately exposed to eight tone-footshock pairings in which the conditional stimulus (CS) either coterminated with a footshock unconditional stimulus (US) (delay conditioning) or was separated from the footshock by a 30-s trace interval (trace conditioning). During trace, but not delay fear conditioning, 0.8 g/kg alcohol impaired learning to a tone CS. This dose also impaired context-dependent learning in both procedures (although only slightly for trace fear conditioning). The 1.6 g/kg alcohol exerted a nonselective impairment on learning. The impairment by alcohol of learning to a tone CS when it is hippocampus-dependent, but not when it is hippocampus-independent provides further support for the hypothesis that alcohol exerts a selective effect on hippocampus-dependent learning.

Acoustic Stimulation↗
PubMed1998

Contextually based conditional discrimination of the rabbit eyeblink response.

Rabbits received conditional discrimination training using contextual stimuli to set the occasion for stimulus pairings during eyelid conditioning. Specifically, animals were exposed to either the presence or the absence of an oscillating chamber light throughout the intertrial interval (50 +/- 10 s). For half the animals, this light signaled paired presentations of a discrete tone conditioned stimulus (CS) and air puff unconditioned stimulus (US) while darkness signaled presentations of only the tone CS. The remaining animals experienced the opposite contextual relationship to the conditioning stimuli. These trial types occurred pseudo-randomly across a session, with all transitions between contextual settings (i.e., light or dark) taking place immediately at the CS-US offset. Under these conditions, animals successfully utilized the contextual stimuli as conditional cues for differential responding to the shared CS. Moreover, both light and dark were equally effective as discriminative stimuli. A subset of animals received further training in which the contextual contingency was removed by restricting all conditioning to the CS-alone context. Without the contingency in place, subsequent CS presentations (paired and CS-alone) evoked equivalent conditioned responding across three sessions of training. Following the reinstatement of the contextual contingencies, discriminatory responding was immediately observed and returned to previous levels within three sessions. Finally, animals appeared to use the static representation of the conditional cue, rather than the phasic transition between cues, for discriminatory responding. These findings are discussed in terms of current neurobiological models of eyelid conditioning.

Analysis of Variance↗
PubMed1989

Conditioned taste preference produced by pairing a taste with a low dose of morphine or sufentanil.

Taste conditioning produced by pairing a taste with low doses of morphine or sufentanil was studied in rats in five experiments. Conditioned taste preferences were obtained with a trace conditioning procedure in which ingestion of a flavored solution was followed by an injection of sufentanil, either 0.25 mcg/kg in experiment 1 or 0.50 mcg/kg in experiment 2. Morphine produced less consistent results than sufentanil. When a similar trace conditioning procedure was used with morphine, a dose of 0.25 mg/kg produced no observable taste conditioning in experiment 3 while 0.42 mg/kg was marginally effective in producing a conditioned taste aversion in experiment 4. In experiment 5, however, conditioning of a taste preference was produced by 0.42 mg/kg morphine with a simultaneous conditioning procedure in which the morphine injection preceded ingestion of the flavored solution. The simultaneous procedure was presumed to facilitate the conditioning of taste preference by minimizing the conditioning of taste aversion.

Analgesics↗
PubMedDate not supplied

Monoaminergic control by amygdalar nuclei of the reinforcing action of conditional stimuli.

The influence of microinfusion of 5-HT, NE, and DA into the amygdalar nuclei on the accomplishment of conditioned reinforcing and conditioned trigger reflexes which are constituents of the CADR was studied in cats with a developed conditioned alimentary discrimination reflex (CADR) in response to two conditional light stimuli set apart on different sides of a box. It was established that 5-HT in doses of 30-50 micrograms in a volume of 5 microliters elicits inhibition; the same doses of NE, by contrast, induces the "hanging-up" of the animals on conditional and conditional--unconditional stimuli which possess the property of reinforcement during the execution of the CADR. The microinfusion of DA in doses of 30-60 micrograms recalls, from animal to animal, the action of 5-HT and NE. It is hypothesized that the inhibitory functions of 5-HT and the activating actions of NE in the amygdalar nuclei support this structure's control of reinforcing conditional and conditional--unconditional reflexes and the perception of the reinforcing action of conditional stimuli. It is hypothesized that the DAergic innervation of the amygdala does not participate directly in conditioned reflex activity.

Amygdala↗
PubMedDate not supplied

Nicotine produces a within-subject enhancement of contextual fear conditioning in C57BL/6 mice independent of sex.

Nicotine enhances learning including contextual fear conditioning. The present study extends previous work on nicotine and conditioned fear to examine the nature of nicotine's enhancement of contextual fear conditioning and sex differences in contextual fear conditioning in C57BL/6 mice using a within-subjects design. Mice were trained by pairing of an auditory stimulus of 80 dB, 6 cps train of broad-band clicks conditioned stimulus (CS) with a 2 sec., 0.35 mA shock unconditioned stimulus (US). Twenty-four hours later mice were tested for freezing in the original context, and one hour later mice were retested in the same context. A 0.5 mg/kg dose of nicotine was given either for three conditions: (1) before training, testing, and retesting; (2) before training and retesting; and (3) before retesting only. The use of a within-subjects design allowed for testing if nicotine would produce state-dependent deficits in contextual fear conditioning. Nicotine did enhance contextual fear conditioning in the groups that received nicotine for both training and testing. Nicotine, however, did not alter freezing when given on training but not testing or testing but not training. No sex differences, however, existed for conditioning or for nicotine's effects on conditioning. These results suggest that nicotine enhanced acquisition and retrieval processes but did not produce state-dependent deficits when administered just for training or just for testing.

Acoustic Stimulation↗
PubMed2003

Apparatus bias and place conditioning with ethanol in mice.

RATIONALE: Although the distinction between "biased" and "unbiased" is generally recognized as an important methodological issue in place conditioning, previous studies have not adequately addressed the distinction between a biased/unbiased apparatus and a biased/unbiased stimulus assignment procedure. Moreover, a review of the recent literature indicates that many reports (70% of 76 papers published in 2001) fail to provide adequate information about apparatus bias. This issue is important because the mechanisms underlying a drug's effect in the place-conditioning procedure may differ depending on whether the apparatus is biased or unbiased. OBJECTIVES: The present studies were designed to assess the impact of apparatus bias and stimulus assignment procedure on ethanol-induced place conditioning in mice (DBA/2 J). A secondary goal was to compare various dependent variables commonly used to index conditioned place preference. METHODS: Apparatus bias was manipulated by varying the combination of tactile (floor) cues available during preference tests. Experiment 1 used an unbiased apparatus in which the stimulus alternatives were equally preferred during a pre-test as indicated by the group average. Experiment 2 used a biased apparatus in which one of the stimuli was strongly preferred by most mice (mean % time on cue = 67%) during the pre-test. In both studies, the stimulus paired with drug (CS+) was assigned randomly (i.e., an "unbiased" stimulus assignment procedure). Experimental mice received four pairings of CS+ with ethanol (2 g/kg, i.p.) and four pairings of the alternative stimulus (CS-) with saline; control mice received saline on both types of trial. Each experiment concluded with a 60-min choice test. RESULTS: With the unbiased apparatus (experiment 1), significant place conditioning was obtained regardless of whether drug was paired with the subject's initially preferred or non-preferred stimulus. However, with the biased apparatus (experiment 2), place conditioning was apparent only when ethanol was paired with the initially non-preferred cue, and not when it was paired with the initially preferred cue. These conclusions held regardless of which dependent variable was used to index place conditioning, but only if the counterbalancing factor was included in statistical analyses. CONCLUSIONS: These studies indicate that apparatus bias plays a major role in determining whether biased assignment of an ethanol-paired stimulus affects ability to demonstrate conditioned place preference. Ethanol's ability to produce conditioned place preference in an unbiased apparatus, regardless of the direction of the initial cue bias, supports previous studies that interpret such findings as evidence of a primary rewarding drug effect. Moreover, these studies suggest that the asymmetrical outcome observed in the biased apparatus is most likely due to a measurement problem (e.g., ceiling effect) rather than to an interaction between the drug's effect and an unconditioned motivational response (e.g., "anxiety") to the initially non-preferred stimulus. More generally, these findings illustrate the importance of providing clear information on apparatus bias in all place-conditioning studies.

Animals↗
PubMed1998

The effects of growth factors and conditioned media on the proliferation of human corneal epithelial cells and keratocytes.

BACKGROUND: As growth factors play an important role in epithelial wound repair, we evaluated the effect of exogenous growth factors in the presence and absence of corneal epithelial and keratocyte conditioned medium on human corneal epithelial cell and keratocyte proliferation. METHODS: Preconfluent cultures of human corneal epithelial cells or stromal keratocytes were exposed to varying concentrations of EGF, TGF-beta or bFGF in the presence or absence of human corneal epithelial or stromal keratocyte conditioned medium. Cell numbers were determined after 48 h incubation. RIA and ELISA were used to quantify the levels of EGF, TGF-beta and bFGF in conditioned media. RESULTS: EGF and bFGF increased, while TGF-beta decreased, the proliferation of both cell types in a dose-dependent manner. Epithelial cell conditioned medium inhibited, and keratocyte conditioned medium stimulated, the proliferation of both cell types. The proliferative effects of EGF, TGF-beta and bFGF in the presence of keratocyte conditioned medium were additive for both cell types. By contrast, the addition of exogenous growth factors was unable to overcome the inhibitory potential of epithelial conditioned medium. Both conditioned media contained significant levels of bFGF, but TGF-beta levels in epithelial conditioned medium were up to 5 times greater than that in keratocyte conditioned medium. CONCLUSIONS: The results indicate that corneal cells maintain tissue homeostasis and modulate the wound healing response via paracrine/autocrine pathways.

Cell Communication↗
PubMed1984

Fear is not critical to classically conditioned analgesia: the effects of periaqueductal gray lesions and administration of chlordiazepoxide.

A high correlation between fear and analgesia classically conditioned to footshock in rats has been reported in the literature. However, it has never been directly tested whether or not fear is in fact causal to the production of conditioned analgesia. We therefore tested whether conditioned analgesia could be elicited in the absence of fear by employing two independent methods of fear suppression. First, areas of the periaqueductal gray (PAG) previously implicated in fear were selectively lesioned. Lesions of the dorsolateral PAG significantly attenuated conditioned analgesia and markedly decreased fear responses. Second, fear was attenuated via administration of chlordiazepoxide (CDP). Rats which had been conditioned while in the presence of CDP showed no reduction in conditioned pain inhibition. These results demonstrate that: (1) fear is not causal to classically conditioned analgesia and (2) the anatomical substrates for fear and conditioned analgesia are distinct but partially overlapping. The fact that fear is not a critical antecedent for classically conditioned analgesia suggests that classical conditioning techniques may be applied clinically to increase the effectiveness of some analgesic manipulations.

Animals↗
PubMed1996

Effects of dopaminergic and glutamatergic receptor antagonists on the establishment and expression of conditioned locomotion to cocaine in rats.

A series of experiments were conducted to investigate the role of dopaminergic D1 and D2 and glutamatergic NMDA and AMPA/kainate receptors on the establishment and expression of cocaine-induced conditioned locomotion in rats. In the first experiment conditioned locomotion was demonstrated by testing the animals in an environment previously associated with 15 mg/kg i.p. cocaine. The D2-receptor antagonist (-)-sulpiride (50 and 100 mg/kg i.p.) administered before cocaine during the conditioning phase did not modify the establishment of conditioned locomotion whereas when administered before testing only at the higher dose it partially reduced rats' locomotion in the absence of cocaine (expression). At the higher dose (0.1 mg/kg i.p.) the D1-receptor antagonist SCH 23390 attenuated the expression of cocaine-induced conditioned locomotion whereas the lower dose (0.03 mg/kg i.p.) had no effect. Both doses of the NMDA receptor antagonist MK-801 (0.125 and 0.25 mg/kg i.p.) blocked the development of cocaine-induced conditioned locomotion but neither dose, when administered before testing, modified locomotion in the absence of cocaine. Both doses of the AMPA/kainate receptor antagonist DNQX administered intracerebroventricularly (1 and 3 micrograms/rat) blocked cocaine-induced conditioned locomotion when given before cocaine during conditioning but when given before testing only the higher dose attenuated the conditioned activity. The results confirm the importance of the interaction between glutamatergic and dopaminergic systems for the conditional factors maintaining drug seeking behaviour. The findings may have implications for the treatment of cocaine craving and relapse.

Analysis of Variance↗
PubMed1994

A new method to assess Pavlovian conditioning of psychostimulant drug effects.

Experimental studies of psychoactive drugs by pavlovian drug-conditioning methods, which originally began with investigations of drug-induced responses mediated by the autonomic nervous system, have now been expanded to include drug-induced response effects expressed as modulations of spontaneous motoric behaviors. In the latter application, however, equivalent behavioral response outcomes in post-treatment tests for conditioning can occur following a psychostimulant drug treatment either through drug interference effects on habituation processes, drug-induced stress effects and/or by pavlovian conditioning of the drug-induced motoric activation effect. Current methodologies for the study of pavlovian conditioned drug effects and/or drug sensitization cannot distinguish among these possibilities. This methodological inadequacy was addressed by a modification of the conventional paired-unpaired treatment protocol. In the new protocol, the animal is sequentially placed into two test compartments with the drug treatment administered in conjunction with placement into the second test compartment. This design permits a differentiation of a pavlovian conditioned drug responses from non-conditioned drug effects through continuous measurement of the non-drug behavioral baseline in both the drug and non-drug control treatment groups combined with multiple response measurements and post-treatment tests for conditioning at variable post-conditioning intervals. The present study details the use of the new modified pavlovian protocol with repeated cocaine (10 mg/kg) treatment. A cocaine conditioned response at 1, 7, and 21 days post-conditioning was identified and distinguished from habituation and stress effects.

Animals↗
PubMed1985

A comparison of the autonomic nervous control of the heart during classical aversive vs appetitive conditioning in dog.

Dogs were trained in either classical (i.e. Pavlovian) appetitive (n = 7) or aversive (n = 7) conditioning by presenting a tone (the conditional stimulus, CS +) that was followed by either food or shock delivery, respectively. In the first case, dog food was given to the animals during the last 30 s of a 1 min CS+. Aversive conditioning was accomplished by giving a 1 s shock at the end of a 30 s CS+. The control consisted of a different tone (CS-) which was never followed by food or shock. A chronically implanted transducer was used to record left ventricular pressure from which its first time derivative was calculated; d(LVP)/dt was used as an index of myocardial inotropic state. Heart rate (HR) was also determined. These data were averaged over the 30 s prior to the CS+, the 30 s of the conditional stimulus tone itself, and the 30 s following shock or during food delivery. Well-trained animals evidenced changes in cardiac inotropism and chronotropism during the CS+ and also in response to unconditional shock or food; these are referred to as the conditional and unconditional cardiovascular responses, respectively. No statistically significant HR or d(LVP)/dt changes were observed during the CS-. The conditional response to food was small: relative to the pre-CS+ interval, average HR increased 11 bpm (P less than 0.05) and average d(LVP)/dt increased 309 mm Hg/s (P less than 0.01). During food delivery, HR increased by additional 23 bpm (P less than 0.01) and d(LVP)/dt increased by another 232 mm Hg/s (P less than 0.01). Beta-adrenergic blockade virtually eliminated the conditional HR and d(LVP)/dt response to food, indicating that both the chronotropic and inotropic changes during CS+ were due to elevated sympathetic drive. beta-blockade did not eliminate the unconditional HR response (+17 bpm, P less than 0.01), indicating that parasympathetic withdrawal has a mediating role in this persisting tachycardia. The conditional response to shock consisted of a 26 bpm increase in HR (P less than 0.01), while d(LVP)/dt increased 998 mm Hg/s (P less than 0.01). The beta-blockade reduced the HR conditional response to +8 bpm (NS) and essentially eliminated the increase in d(LVP)/dt. These data indicate that increases in cardiac sympathetic tone play a primary role in mediating the conditional cardiovascular response for both paradigms. Parasympathetic withdrawal, on the other hand, figures critically in mediating the unconditional response to food.

Animals↗
PubMed1994

Cooling-induced retrograde amnesia reflexes Pavlovian conditioning associations in Limax flavus.

The relationships between cooling-induced retrograde amnesia and associations in Pavlovian conditioning in the terrestrial mollusk Limax flavus were studied. In the first experiment, the slugs were conditioned to avoid carrot odor and the experimental conditions required for amnesia induction were studied. Memory reactivation before cooling was found to be necessary for amnesia induction and the induced amnesia was selective for the reactivated memory. In the subsequent experiments, slugs were conditioned to avoid both carrot and cucumber odors using one of three Pavlovian conditioning paradigms, namely two-independent first-order conditioning, phase-2-sequential second-order conditioning and phase-2-simultaneous second-order conditioning, after which amnesia was induced by cooling immediately after presentation of one of the conditioning odors. The amnesia pattern induced differed depending upon the conditioning procedure used, which indicated that amnesia induction was related closely to stimulus associations in slugs. The possible role of cooling-induced retrograde amnesia as a tool for studying memory associations is also discussed.

Amnesia, Retrograde↗
PubMed1986

Memory formation in birds: 1. Avoidance conditioning of the budgerigar (Melopsittacus undulatus) to sound stimuli.

A system is described for avoidance conditioning of the budgerigar (Melopsittacus undulatus), for sound patterns consisting of one or two sequential subunits and to discriminate between two closely resembling sounds. Electric shock was used as the unconditioned stimulus. Simple conditioning was accomplished in about 300-400 trials. After a given sound pattern was firmly fixed by conditioning, discrimination between this and a new sound pattern was established relatively rapidly by using several consecutive sessions in which the two patterns were mixed. Discrimination was reinforced by associating the two signals by opposing electric shocks. An overnight rest period after the first few sessions improved the rate of conditioning during the following experimental period. A temporary, partial or complete extinction of conditioning was produced by longer rest intervals, but the original conditioning was reestablished by subjecting the animal to a few trials of reconditioning. Short intercalations of a new conditioned stimulus had no effect on the retention of the original conditioning whereas a random mixing of the first conditioned stimulus with a second produced a temporary decay in the original conditioning. The experimental system described here is useful for studying physiological and biochemical changes accompanying a memory process based on a linear sequence of sound patterns.

Animals↗