Discrete CS Research Articles

‘That Tricky Subject’: The Integration of Contextual Studies in pre‐Degree Art and Design Education

AbstractContextual studies (CS), ‘theory’, ‘visual culture’ or ‘art history’ (amongst other labels) refer to a regular and often compulsory feature in art and design education. However, this takes many forms and can sit in a variety of relationships with the practical elements of such courses. This article is based on mixed method research on CS in the BTEC Extended Diploma in Art and Design, a course that makes up a substantial proportion of pre‐degree provision in the UK. We describe aspects of the wider study then draw on two cases to illustrate and discuss the implications of different approaches to the curriculum and its integration. Our analysis suggests that a seemingly progressive flight from a discrete CS towards a designed form of integration can have unintended negative consequences, and in the light of this we suggest some ways in which course teams might reflect on their practices.

Occasion setting by drug states: Functional equivalence following similar training history

Three experiments examined whether a drug state serving as a positive feature for pairings between a discrete conditional stimulus (CS, 15-s light or 15-s noise) and sucrose could transfer facilitative control to a CS with which it had never been presented. To do so, a CS was paired with a sucrose reward in the nicotine (0.4mg/kg), amphetamine (AMP, 1mg/kg), or chlordiazepoxide (CDP, 5mg/kg) drug state; in separate saline sessions the CS was presented but was not followed by any reward. All three drug states facilitated responding to a discrete CS; previous studies found that this facilitation did not depend on direct associations between the drug state and sucrose. When a second discrimination was trained (e.g., CDP: light-sucrose and nicotine: noise-sucrose) the drug states facilitated responding to the CS trained in that state (nicotine: noise) as well as the CS normally presented in the other drug state (e.g., nicotine: light). A novel drug state (e.g., amphetamine) did not affect responding to either CS, indicating that the originally trained drug states had acquired functional similarity based on learning history. Also, a novel or ambiguous CS did not evoke responding in the previously trained drug state, indicating that both the features (drug states) and target conditional stimuli had to be trained in discriminations before transfer could occur.

Inhibition of neurogenesis interferes with hippocampus‐dependent memory function

Rats treated with low dose irradiation, to inhibit adult hippocampal neurogenesis, and control rats were administered a non-matching-to-sample (NMTS) task, which measured conditional rule learning and memory for specific events, and a test of fear conditioning in which a discrete CS was paired with an aversive US in a complex environment. Irradiated rats were impaired on the NMTS task when the intervals between sample and test trials were relatively long, and in associating the shock-induced fear with contextual cues in the fear conditioning task. Irradiated rats were not impaired in learning the basic NMTS rule or in performing that task when the intervals between the sample and test trials were short. Nor were there group differences in conditioning the fear response to the CS in the fear conditioning task. The results, which extend the range of hippocampus-dependent tasks that can be said to be vulnerable to the effects of neurogenesis suppression, support the hypothesis that new hippocampal cells generated in adulthood participate in a broad range of hippocampal functions.

The hippocampus and appetitive Pavlovian conditioning: Effects of excitotoxic hippocampal lesions on conditioned locomotor activity and autoshaping

The hippocampus (HPC) is known to be critically involved in the formation of associations between contextual/spatial stimuli and behaviorally significant events, playing a pivotal role in learning and memory. However, increasing evidence indicates that the HPC is also essential for more basic motivational processes. The amygdala, by contrast, is important for learning about the motivational significance of discrete cues. This study investigated the effects of excitotoxic lesions of the rat HPC and the basolateral amygdala (BLA) on the acquisition of a number of appetitive behaviors known to be dependent on the formation of Pavlovian associations between a reward (food) and discrete stimuli or contexts: (1) conditioned/anticipatory locomotor activity to food delivered in a specific context and (2) autoshaping, where rats learn to show conditioned discriminated approach to a discrete visual CS+. While BLA lesions had minimal effects on conditioned locomotor activity, hippocampal lesions facilitated the development of both conditioned activity to food and autoshaping behavior, suggesting that hippocampal lesions may have increased the incentive motivational properties of food and associated conditioned stimuli, consistent with the hypothesis that the HPC is involved in inhibitory processes in appetitive conditioning.

Evidence of Selective Learning Deficits on Tests of Pavlovian and Instrumental Conditioning in α-CaMKIIT286A Mutant Mice

Mice carrying a threonine286 to alanine mutation in subunit α of Ca2+/CaM-dependent protein kinase II (α-CaMKIIT286A) have been reported to show deficits in hippocampal long-term potentiation as well as spatial learning deficits similar to those induced in mice with hippocampal lesions. In this series, we sought to extend this analysis by investigating the performance of α-CaMKII mutants on other, potentially hippocampal, learning tasks. Experiment 1 examined fear conditioning, Experiment 2 examined the acquisition of free-operant instrumental conditioning and its dependence upon the action-outcome association, and Experiment 3 assessed interval timing using an instrument version of the peak procedure.We found evidence of a deficit in contextual fear conditioning in Experiment 1 and in peak timing in Experiment 3, but neither a deficit in fear conditioning to a discrete tone CS nor in the acquisition of instrumental conditioning in Experiment 2. Furthermore, all of the mice in Experiment 2 showed a normal instrumental outcome devaluation effect, suggesting that encoding of the action-outcome association was unaffected by this point mutation. It appears, therefore, that although learning in CaMKII mutants is affected on specific tasks, they do not have a general learning deficit, and that the influence of this mutation, and therefore, of α-CaMKII, is both localized anatomically and relatively specialized functionally.

Effect of Sex on Fear Conditioning is Similar for Context and Discrete CS in Wistar, Lewis and Fischer Rat Strains

Enhanced fear in males relative to females, both innate and conditioned, is a well-described characteristic of behavior in the laboratory rat. In the case of aversive conditioning to foot shock in Long–Evans rats, it has been described that conditioning to general (nondiscrete) contextual cues is greater in male rats relative to female rats, whereas conditioning to a discrete, predictive stimulis (CS) is not. These findings have been combined with evidence for greater levels of hippocampal LTP in males in Sprague–Dawley rats to derive a model of hippocampal–LTP-mediated contextual and not CS, fear conditioning. The present study reports on an analysis of the effect of sex in contextual and discrete CS conditioning to foot shock, assessed via measurement of freezing behavior in a novel automated paradigm, in three rat strains: Wistar, Fischer, and Lewis. In Wistar rats, there was a consistent but nonsignificant tendency for males to demonstrate both more contextual and more CS conditioning than females; in Fischer rats, males demonstrated both more contextual and more CS conditioning than females; in Lewis rats, a markedly enhanced acquisition of freezing in males did not translate into a sex difference in either context or CS conditioning at expression. Therefore, within each strain the effect of sex was consistent between context and CS conditioning. These findings, taken together with the hippocampal LTP evidence, suggest that the latter mediates both contextual and discrete CS aversive conditioning, and contributes to sex differences in both these forms of conditioning, in those strains where these sex differences exist.

Blocking of the Rabbit's Classically Conditioned Nictitating Membrane Response: Effects of Modifications of Contextual Associative Strength

The effects of contextual manipulations on the magnitude of discrete cue blocking of the rabbit's nictitating membrane response were investigated in three experiments. Experiment 1 showed that changing or extinguishing the single stimulus training context prior to compound training attenuated the blocking effect. In contrast, extinction of the context following compound conditioning did not attenuate blocking. In Experiment 2, attenuation of blocking was found to be greater following extinction of both the discrete CS and the context, in comparison to extinction of the discrete cue alone. Interpolation of US-alone presentations (context conditioning) between single stimulus training and compound conditioning produced no effects. In Experiment 3, enhanced responding to the blocked stimulus was observed following a retention interval interposed between compound training and testing. However, the blocking effect was preserved if subjects were repeatedly exposed to training context cues during the interval (i.e., context extinction) and tested in the presence of those cues. The results of the present investigation support the conclusion that the CS complex producing the blocking effect is composed of both discrete and contextual components. The observed effects were discussed in terms of associative and comparator models of conditioning.

Conditioned changes in pain reactivity I: A discrete CS elicits hypoalgesia, not hyperalgesia, on the tail-flick test

Prior work suggests that a stimulus which has been paired with an aversive event may elicit either an increase or decrease in pain reactivity. In four experiments we attempted to isolate the variables which determine the direction of the conditioned response. In all experiments, one stimulus was paired with shock (the CS+) while another was nonreinforced (the CS−). Pain reactivity was assessed by measuring tail withdrawal from radiant heat (the tail-flick test). Experiment 1 tested whether the amount of training plays a critical role. We found that the CS+ elicits longer tail-flick latencies irrespective of whether subjects received 6 or 24 CS-US pairings. Although there was some evidence that subjects may exhibit a general hyperalgesia at 2 min after the presentation of the conditioned stimulus, the results of Experiment 2 revealed that this effect was an artifact caused by differences in the amount of time between test trials. The results of Experiment 2 also showed that the difference observed between the CS+ and CS− was not due to a CS− induced hyperalgesia. Rather, it reflects a CS+ induced hypoalgesia. Experiment 3 evaluated whether the time of day at which testing occurs is important. We found that subjects exhibit conditioned hypoalgesia when tested in either the light or dark portion of the light-dark cycle. In Experiment 4 we examined whether it matters if subjects are tested in the training context or a neutral context. We found that subjects exhibit conditioned hypoalgesia during the CS+ irrespective of where they are tested. The results suggest that a CS+ elicits hypoalgesia, not hyperalgesia, on the tail-flick test over a wide range of conditions.

Plasma production in a Cs vapour via single-photon ionisation with excimer laser light

Efficient plasma production by direct single-photon ionisation (SPI) with the 308 nm XeCl laser line has been observed in dense Cs vapour in a heat pipe oven. The optical spectra of the resulting plasma consist of discrete Cs lines and of recombination continua. High amplitude of the continua, Stark broadening of the allowed Cs lines and appearance of forbidden ones together with sputtering in a weak dc electric field are indications of a very high degree of ionisation of the Cs vapour. With the assumption of a local thermodynamic equilibrium the electron density and temperature are estimated to be N e = (5±1)×10 13 cm -3 and T e = 0.153±0.010 eV, respectively. Strong inhomogeneities of the Cs vapour density and Cs cluster formation in the overheated heat pipe oven, associated with convective vapour flow, have also been observed. Finally, some remarks are added on laser-stimulated electron-ion recombination after the SPI.

The effects of ITI fillers in autoshaping

The present experiments used pigeons in an autoshaping procedure to examine the effects of a nonreinforced, nontarget stimulus presented during the intertrial interval on responding to a target CS. Experiments 1 and 2 found that a filler stimulus presented during a substantial portion of the ITI retarded responding to the target CS relative to a group not exposed to the filler. This group difference in performance was subsequently abolished by continued training and omitting the filler in the former group (Experiment 1) or adding a filler for the latter group (Experiment 2). Experiment 3 found that when the “filler” occupied most of the interreinforcement interval, CS-US pairings embedded within the “filler” stimulus yielded superior autoshaping relative to a group that received CS-US pairings embedded in static apparatus cues in the absence of the filler. The results are discussed with reference to the ways that a nontarget stimulus during the ITI can influence contextual modulation of responding to a discrete CS and the necessity for comparator theories to incorporate a “local context” view of cycle time to explain the present findings.

Associative aspects of conditioned analgesia evoked by a discrete CS

Four experiments with rat subjects assessed conditioned analgesia evoked by a discrete visual CS repeatedly paired with a shock US. In Experiment 1, rats that received CS-US pairings followed by a hot-plate test of pain sensitivity in the presence of the CS showed significantly longer response latencies than groups of rats receiving a variety of Pavlovian control procedures, including CS and US explicitly unpaired, CS-alone, US-alone, and apparatus-alone. Experiment 2 showed that two CS-US pairings were required for the CS to evoke conditioned analgesia and that additional CS-US pairings did not augment the observed analgesia. Experiment 3 demonstrated extinction of conditioned analgesia in groups that received CS-alone presentations. Experiment 4 found that conditioned analgesia established with the present procedures was unaffected by prior administration of the opiate receptor antagonist naloxone. Experiments 1 and 3 also demonstrated a number of situations in which freezing behavior (used to index conditioned fear) could be dissociated from hot-plate response latencies (used to index conditioned analgesia). These results are discussed in terms of how associative learning processes mediate acquisition of conditioned analgesia.

Variations in explicitly unpaired training are differentially effective in producing conditioned inhibition

To evaluate a contingency interpretation of conditioned inhibition (CI), rats were given “explicity unpaired” training in which the locus and duration of a CS within the inter-US (shock) interval were systematically manipulated for different groups. Summation and retardation tests in Experiment 1 indicated that stronger CI resulted from both a backward and a trace CS than from a midlocus CS of equal or greater duration. Complementing these findings, the same tests in Experiment 2 showed that, by comparison with novel-stimulus controls, CI developed to a trace CS but not to a mid-locus CS, nor to a trace CS that was accompanied by an immediate signal for the US. These findings argue against a contingency interpretation of CI and favor a contiguity interpretation stressing the short-term rehearsal of stimulus events. Such rehearsal of the US allows a backward CS, but not a mid-locus CS with an extended US-CS interval, to be discriminated as a signal for nonreinforcement, and thus to develop as a conditioned inhibitor. Similarly, excitatory conditioning to the memory trace of a CS allows the nominal trace CS to develop as a signal for nonreinforcement, and thus as a conditioned inhibitor, but not when its memory trace is overshadowed by another CS that immediately precedes the US. In short, the development of CI is facilitated when excitation is mediated by the memorial processing of either the US or a discrete CS for the US rather than by contextual cues.

Mechanisms of blocking by contextual stimuli

The influence of contextual stimuli on the conditioning and performance of responding to a discrete stimulus was examined in the US preexposure paradigm using both context shift manipulations and a measure of context conditioning. Four groups of rats received both repeated exposure to an electric shock US in one context (Context 1), and repeated nonshocked exposure to a second context (Context 2). Two additional groups of rats received exposure to these contexts, but never received shock presentations. Rats exposed to shock learned to escape from the stimuli of Context 1, but did not escape from the stimuli provided by Context 2. Rats not exposed to shock failed to escape from either context. All rats then received a single CER conditioning session in which four pairings of a 3-min noise CS and shock US were presented. Half the rats received those CS-US pairings in the excitatory Context 1, while the remaining rats received those pairings in the neutral Context 2. Finally, half the rats in each of the CER conditioning treatments received extinction test trials of the noise CS in Context 1, while the remaining rats received those test trials in Context 2. Thus, this design factorially manipulated the presence of excitatory or neutral contextual stimuli during both conditioning and testing of a discrete CS. In comparison with the two groups of rats never preexposed to shock alone, attenuation in acquisition of conditioned suppression observed during test trials occurred only when CER conditioning had been administered in the excitatory Context 1, and this effect was manifested when testing occurred in either the excitatory Context 1 or the neutral Context 2. These results support the model of R. A. Rescorla and A. R. Wagner (1972) (in A. H. Black & W. F. Prokasy (Eds.) Classical Conditioning II, pp. 64–99, New York: Appleton-Century-Crofts) which asserts that contextual stimuli and sicrete CSs compete for limited associative strength supportable by a given US.

The US preexposure phenomenon in the conditioned suppression paradigm: A role for conditioned situational stimuli

Four experiments evaluated possible associative and nonassociative accounts of the retardation in the acquisition of conditioned suppression produced by repeated prior exposure to an electric shock US. Associative interference resulting from conditioning of situational stimuli during preexposure to shock was suggested by the findings that signaling the occurrence of high-intensity shock with a discrete nontarget CS during the preexposure phase reduced the magnitude of the retardation effect compared to an unsignaled shock preexposure treatment (Experiments 1 and 4), nonreinforced presentations of putatively conditioned situational stimuli prior to conditioned suppression training reduced the magnitude of the retardation effect (Experiment 2), and the magnitude of the retardation effect was directly related to the intensity of preexposure shock (Experiment 3). Nonassociative interference was suggested by the finding that signaling the occurrence of low-intensity shock with a discrete nontarget CS during the preexposure phase did not reduce the magnitude of the retardation effect compared to an unsignaled shock preexposure treatment (Experiment 4). It was suggested that associative and nonassociative mechanisms govern the US preexposure phenomenon obtained in the conditioned suppression paradigm, and their relative contribution depends upon the intensity of shock.

Conditioned inhibition of fear: Evidence for a competing response mechanism

In two experiments, inhibitory conditioning was attempted by presenting a discrete CS in a neutral stimulus environment shortly following the termination of either shock (Experiment 1) or a second discrete CS which had been paired in a forward manner with shock (Experiment 2). Evidence of successful inhibitory conditioning was mixed in Experiment 1, where the properties of the CS were assessed within an escape-from-fear procedure. Postresponse presentations of the CS enhanced performance, whereas the presentation of the CS prior to responding did not have the expected degrading effect on performance. In Experiment 2, the inhibitory properties of the CS were assessed by combining this stimulus with an excitatory CS and presenting the compound to rats engaged in a water-reinforced licking response. Less response suppression was found in reaction to this compound relative to three separate comparison conditions, thus witnessing the success of the inhibitory-conditioning procedure used. The common assumption that inhibitory conditioning results from the nonreinforcement of a CS in a situation where reinforcement is expected, i.e., one which contains previously reinforced cues, is not supported by these data, for no previously reinforced cues were simultaneously presented with the CS during inhibitory training. The data are in agreement with a conditioned antagonistic-response interpretation of inhibitory conditioning.

The Effects of Manipulation of the CS and Variations in the Duration of Response Prevention on Extinction of Avoidance Responses

Rats were trained to avoid 0.5 mA shock and, following learning, were divided into two groups ‐ control and experimental. Following acquisition trials, the control animals were left in the shuttle box for 5 min and the experimental animals were removed from the shuttle box and placed in a plastic pail. The CS was presented continuously for 5 min. The rats were then returned to the shuttle box and extinction trials began. The results showed that response prevention was ineffective when it occurred in the presence of the discrete CS. After learning to avoid 0.5 mA shock, animals in the second experiment were divided into the following four groups: controls and three groups which received response prevention for 10 sec, 3 min and 5 min, respectively. The results showed that there was no significant difference between the groups. Clinical implications of the results of both experiments are discussed.

Counterconditioning and exposure-only in the treatment of specific (conditioned suppression) and generalized fear in rats

In Experiment 1 the conditioned suppression technique was used to condition specific fear, suppression of operent lever pressing for food to a discrete CS. The efficacy of four treatment conditions on fear reduction was evaluated. Counterconditioning in which exposure to the CS was contiguously paired with food was significantly less effective than noncontiguous CS exposure and food. An exposure-only effect was indicated by the superiority of all three treatments involving CS exposure (the above two plus a typical conditioned suppression extinction procedure) to treatment consisting of food only. The reverse counterconditioning effect and the exposure effect are consistent with current views that emphasize the centrality of aversive stimulus exposure in fear reduction. Experiment 2 investigated elimination of generalized fear produced by unsignalled, inescapable shocks in the lever-pressing apparatus. Two treatments (counterconditioning and exposure-only) were equally effective and they were superior to no exposure control treatment. The results of the two experiments reinforce recent attempts toward a reevaluation of the role of anxiety-competing responses in elimination of fear.

Escape behavior as determined by schedules of shock and discrete CS presentations

Rats received escape training, with shock-presentation schedules of 50% or 100% and discrete CS-presentation schedules of 0%, 50% or 100%, followed by extinction with the discrete CS alone. Acquisition performance was directly related to shock percentage (p < .001). No reliable effect of CS was found. Resistance to extinction was inversely related to shock percentage (p <. 05) and, during early extinction, was directly related to CS percentage (p < .02 on extinction Trial Block 1).