Visual input regulates circuit configuration in courtship conditioning of Drosophila melanogaster

Courtship and courtship conditioning are behaviors that are regulated by multiple sensory inputs, including chemosensation and vision. Globally inhibiting CaMKII activity in Drosophila disrupts courtship plasticity while leaving visual and chemosensory perception intact. Light has been shown to modulate CaMKII-dependent memory formation in this paradigm and the circuitry for the nonvisual version of this behavior has been investigated. In this paradigm, volatile and tactile pheromones provide the primary driving force for courtship, and memory formation is dependent upon intact mushroom bodies and parts of the central complex. In the present study, we use the GAL4/UAS binary expression system to define areas of the brain that require CaMKII for modulation of courtship conditioning in the presence of visual, as well as chemosensory, information. Visual input suppressed the ability of mushroom body- and central complex-specific CaMKII inhibition to disrupt memory formation, indicating that the cellular circuitry underlying this behavior can be remodeled by changing the driving sensory modality. These findings suggest that the potential for plasticity in courtship behavior is distributed among multiple biochemically and anatomically distinct cellular circuits.     

Second-order conditioning in Drosophila

Associative conditioning in Drosophila melanogaster has been well documented for several decades. However, most studies report only simple associations of conditioned stimuli (CS, e.g., odor) with unconditioned stimuli (US, e.g., electric shock) to measure learning or establish memory. Here we describe a straightforward second-order conditioning (SOC) protocol that further demonstrates the flexibility of fly behavior. In SOC, a previously conditioned stimulus (CS1) is used as reinforcement for a second conditioned stimulus (CS2) in associative learning. This higher-order context presents an opportunity for reassessing the roles of known learning and memory genes and neuronal networks in a new behavioral paradigm.     

The role of contingency in classical conditioning

The assumption that classical conditioning depends on a contingent relation between the conditioned stimulus (CS) and the unconditioned stimulus (US), which was proposed some decades ago as an alternative to the traditional contiguity assumption, still is widely accepted as an empirical generalization, if no longer as a theoretical postulate. The first support for the contingency assumption was provided by experiments in which occasional CS-US pairings produced no response to the CS in random training--i.e., training in which the probability of the US was the same in the presence and absence of the CS. Those early experiments, the results of which too often are taken at face value, are reconsidered along with various later experiments that show conditioning, both of the CS and its context, in random training. The evidence suggests that CS-US contingency is neither necessary nor sufficient for conditioning and that the concept has long outlived any usefulness it may once have had in the analysis of conditioning.     

The role of awareness in human conditioning

The cognitive view of human classical conditioning is that Ss are active in thinking about the pattern of stimulus events which occurs, the demands of the situation, and the kind of responses which they give. A question crucially central to conditioning theory is whether these thoughts and expectations determine conditional responding. This paper reports on two conditioning and personality experiments, employing the standard procedure of a single cue CS-UCS schedule and masking task, which assess awareness of stimulus contingencies and demand characteristics by means of a postexperimental questionnaire. Results were quite clear in showing no significant relationship between measures of awareness and eyelid conditioning.     

Excitatory conditioning of individual Drosophila melanogaster

Testing individual animals from a heterogenic population of Drosophila melanogaster, we demonstrate conditioning of the proboscis extension reflex. The presentation of paired (conditioning) stimuli produced (a) an increase in the average number of conditioned responses over trials, (b) measured differences in performance levels among individual subjects, and (c) a sex difference, with more males conditioned than females, and those that did did so more quickly. The presentation of unpaired (control) stimuli produced significantly lower average levels of acquisition responding and a change in the distribution of individual response patterns. Neither central excitatory state nor sensitization induced by the conditioned or unconditioned stimuli directly affected the conditioned response, whereas unconditioned stimulus preexposure adversely affected performance levels. Presenting the unpaired (extinction) stimuli after conditioning produced less of a decline in responding than did an extinction procedure with removal of the unconditioned stimulus. With the ability to identify individual differences in acquisition and extinction patterns, and given the relatively large number of individuals that can be tested simultaneously on the automated stimulation apparatus, it is now possible to make precise behavioral measurements on samples large enough for the behavior-genetic analysis of D. melanogaster with conditioning as the phenotype.     

The role of CS-US contingency in human evaluative conditioning

Recent studies suggest that in Pavlovian conditioning, two different processes may be operative: signal learning and evaluative learning, resulting in two qualitatively different associative structures. Signal-learning is hypothesized to be responsible for providing us with genuine predictors (CS) for significant events (US). This proposition logically entails that the statistical-correlational relation, i.e. the contingency between CS and US should be a crucial determinant of signal learning. Evaluative conditioning, on the other hand, refers to the observation that the mere pairing of neutral with (dis)liked stimuli changes the valence of the originally neutral stimuli in a (negative) positive direction. As argued elsewhere, evaluative conditioning is probably based on the CS acquiring a mere referential value to the US, without any genuine CS-US expectancy being involved. From this, it was hypothesized that evaluative conditioning might not be dependent on CS-US contingency. Using the standard evaluative conditioning paradigm, four different levels of CS-US contingency were created on a between-subject base. The overall effect of evaluative conditioning was strongly significant, and was not mediated by awareness of the CS-US relation. Of crucial importance, this conditioning effect did not interact with the level of contingency, supporting the hypothesis that CS-US contingency is not a crucial determinant of evaluative conditioning. Moreover, this effect was obtained in a situation in which Ss simultaneously evidenced to have consciously registered quite accurately the different levels of CS-US contingency.     

The role of background stimuli during pavlovian conditioning

An investigation was carried out into the part played by background stimuli during Pavlovian conditioning. Groups of rats were presented with tone CSs and unavoidable foot-shock USs. Both CS-US conditional probabilities and US intensity were manipulated across groups. Subsequently all animals were tested for their reactions to the environment in which they had previously been trained. During tests neither the CS nor the US was presented. It was found that the degree to which rats avoided the environment was inversely related to the probability of the CS being followed by a US and directly related to the level of US intensity to which they had been exposed during training. The results largely supported Rescorla and Wagner's (1972) theory of Pavlovian conditioning.     

The role of context in the inhibitory conditioning of honeybees

Conditioned inhibition or CI training (A+/AB-) was compared with S- training (A+/B-) in three experiments on proboscis-extension conditioning in harnessed honeybees. The purpose was to test the Rescorla-Wagner assumption, widely credited in the vertebrate literature, that a nonreinforced stimulus acquires inhibitory properties in proportion to the excitatory value of the context in which it is presented. In prior work with free-flying honeybees pretrained with sucrose to come of their own accord to the experimental situation, no differences were found in the consequences of CI and S- training, perhaps because A added little to the excitatory value of the context (already very high) in which B occurred. In the new experiments, with harnessed subjects brought involuntarily into the training situation, negative results again were obtained. The possibility is considered that inhibitory conditioning in honeybees is independent of the excitatory value of the context.     

The role of cue additivity in salience in taste aversion conditioning

In toxiphobia conditioning certain cues are more easily associated with malaise (i.e., more salient) than others. The present experiments show that cue additivity can account for previously found differences in salience of certain fluids. The relative salience of saccharin, saline and casein hydrolysate was tested in normal rats and in animals rendered anosmic by treatment of their nasal passages with zinc sulphate. The normally more salient casein was reduced in salience to the same level as saccharin and saline in the anosmic animals, while anosmia did not affect the relative salience of saccharin and saline. A second study tested the cue properties of vanilla, a fluid of very low salience. Anosmic animals could not show a conditioned aversion to vanilla. Normal animals readily learned the aversion but could not show it following a later anosmia treatment. Anosmia did not disrupt a saccharin aversion previously conditioned in normal animals. The data show that some of the “tastes” used in toxiphobia conditioning have olfactory components, and some are purely olfactory. Further, olfactory cues can summate with taste cues to form a more salient stimulus.     

The moderating role of attribute accessibility in conditioning multiple specific attributes

Attribute conditioning (AC) refers to people's changed assessment of stimuli's (conditioned stimuli, CSs) attributes due to pairings with stimuli possessing these attributes (unconditioned stimuli, USs). Up to now, research only showed conditioning of only one attribute within a conditioning session (e.g., athleticism) and measured assessment changes in only this single attribute. The current study shows attribute‐specific AC effects in multi‐attribute environments and shows that attribute accessibility determines which of a US's multiple attributes are conditioned. Experiment 1 shows AC effects for artificial logos with attributes varying across USs (e.g., athletic, intelligent, or funny). Experiment 2 shows that these AC effects persist over time. Experiment 3 directly manipulated accessibility for attributes varying between and within USs (e.g., a US being sexy and familial) with a priming procedure. Priming‐specific attributes prior to conditioning determined which attribute of a US was conditioned to paired CSs. We discuss theoretical implications for AC, as well as practical implications for brand image formation and advertising. Copyright © 2013 John Wiley & Sons, Ltd.     

Genetic architecture of olfactory discriminative avoidance conditioning in Drosophila melanogaster

Recent claims to have demonstrated associative learning ability in Drosophila melanogaster raise questions about the adaptive significance of behavioral modifiability of this species. In a strain survey and a 9 X 9 half diallel cross study of olfactory discriminative avoidance conditioning, a low narrow heritability and strong directional dominance or heterosis controlling nonrandom phenotypic variation were found. Furthermore, the predicted inbreeding depression and asymmetrical response to bidirectional genetic selection were both observed. The genetic architecture revealed in these experiments is consistent with a close association between this conditioning phenotype and evolutionary fitness. Predictions from this interpretation to the nature of new mutations have been confirmed, and a possible role for conditioning in courtship behavior has been identified.     

The role of awareness in delay and trace fear conditioning in humans

Expression of conditional fear without awareness has been previously demonstrated during delay conditioning, a procedure in which the conditioned stimulus (CS) and unconditioned stimulus (UCS) overlap. However, less is known about the role of awareness in trace fear conditioning, where an interval of time separates the CS and UCS. The present study assessed skin conductance response (SCR) and UCS expectancy during delay and trace conditioning. UCS predictability was varied on a trial-bytrial basis by presenting perithreshold auditory CSs. Differential UCS expectancies were demonstrated only on perceived delay and trace trials. Learning-related SCRs were observed during both perceived and unperceived delay CSs. In contrast, differential SCRs were demonstrated only for perceived trace CSs. These data suggest that awareness is necessary for conditional responding during trace, but not delay, fear conditioning.     

Substantia nigra role in fear conditioning consolidation

The substantia nigra (SN) is known to be involved in the memorization of several conditioned responses. To investigate the role of the SN in fear conditioning consolidation this neural site was subjected to fully reversible tetrodotoxin (TTX) inactivation during consolidation in adult male Wistar rats which had undergone fear training to acoustic CS and context. TTX was stereotaxically administered to different groups of rats at increasing intervals after the acquisition session. Memory was assessed as conditioned freezing duration measured during retention testing, always performed 72 and 96 h after TTX administration. In this way there was no interference with normal SN function during either acquisition or retrieval phases, so that any amnesic effect could be due only to consolidation disruption. The results show that SN functional integrity is necessary for contextual fear response consolidation up to the 24-h after-acquisition delay. On the contrary SN functional integrity was shown not to be necessary for the consolidation of acoustic CS fear responses. The present findings help to elucidate the role of the SN in memory consolidation and better define the neural circuits involved in fear memories.     

Sex role conformity in homosexual and heterosexual males

Nine principal components were extracted from the scores of 26 homosexual and 26 heterosexual males matched on age, education, occupation status, and sampling frame on Adjective Check List, Bem Sex Role Inventory, Chapin Social Insight Test, Experience Inventory, and Sixteen Personality Factor Questionnaire scales selected to represent a variety of "masculine" and "feminine" sex role attributes. The four most general varimax factors, accounting for 48% of the total variance, were: I) "Feminine Openness," II) "Masculine Boldness," III) "Reflection," and IV) "Novelty Seeking." Factor scores were constructed and indicated that the homosexual sample was significantly more identified with Factor I (p < .00l; 17% of total variance). There was no significant difference between the samples on Factor II, nor on the remaining two general factors which were not sex typed.     

The role of the cs and avoidance period duration in discriminated avoidance conditioning

In an experiment investigating the effect of CS duration on discriminated bar-press conditioning, subjects were assigned to one warning period duration (1.5, 5.0 or 15.0 sec.) on the first day of avoidance training, and to one of the three durations on the second day of training. On each day avoidance behaviour was greatly influenced by the duration of the CS (warning) period, but the duration on day I had no effect on the second day's avoidance performance. Groups receiving no CS during training, although provided an avoidance contingency, showed little conditioning, but produced highly significant amounts of intertrial responding. In a second experiment, subjects receiving CS on day I were shifted to no CS on day II. Avoidance performance on day II was not significantly different from the day II performance of subjects in Experiment I having two training sessions with the CS present or absent on both days.     

The role of awareness in Pavlovian conditioning: empirical evidence and theoretical implications

This article reviews research over the past decade concerning the relationship between Pavlovian conditioning and conscious awareness. The review covers autonomic conditioning, conditioning with subliminal stimuli, eyeblink conditioning, conditioning in amnesia, evaluative conditioning, and conditioning under anesthesia. The bulk of the evidence is consistent with the position that awareness is necessary but not sufficient for conditioned performance, although studies suggestive of conditioning without awareness are identified as worthy of further investigation. Many studies have used inadequate measures of awareness, and strategies for increasing validity and sensitivity are discussed. It is concluded that conditioning may depend on the operation of a propositional system associated with consciousness rather than a separate, lower level system.