Suppression Of Licking In Rats Research Articles

Editorial: Extinction Learning from a Mechanistic and Systems Perspective.

Editorial: Extinction Learning from a Mechanistic and Systems Perspective.

Long-term treatment with standardized extract of Ginkgo biloba L. enhances the conditioned suppression of licking in rats by the modulation of neuronal and glial cell function in the dorsal hippocampus and central amygdala

Our group previously demonstrated that short-term treatment with a standardized extract of Ginkgo biloba (EGb) changed fear-conditioned memory by modulating gene expression in the hippocampus, amygdaloid complex and prefrontal cortex. Although there are few controlled studies that support the long-term use of EGb for the prevention and/or treatment of memory impairment, the chronic use of Ginkgo is common. This study evaluated the effects of chronic treatment with EGb on the conditioned emotional response, assessed by the suppression of ongoing behavior and in the modulation of gene and protein expression. Male adult Wistar rats were treated over 28days and assigned to five groups (n=10) as follows: positive control (4mgkg−1 Diazepam), negative control (12% Tween 80), EGb groups (0.5 and 1.0gkg−1) and the naïve group. The suppression of the licking response was calculated for each rat in six trials. Our results provide further evidence for the efficacy of EGb on memory. For the first time, we show that long-term treatment with the highest dose of EGb improves the fear memory and suggests that increased cAMP-responsive element-binding protein (CREB)-1 and glial fibrillary acidic protein (GFAP) mRNA and protein (P<0.001) in the dorsal hippocampus and amygdaloid complex and reduced growth and plasticity-associated protein 43 (GAP-43) (P<0.01) in the hippocampus are involved in this process. The fear memory/treatment-dependent changes observed in our study suggest that EGb might be effective for memory enhancement through its effect on the dorsal hippocampus and amygdaloid complex.

Initial excitatory conditioning with the truly random control procedure in rats: The effects of density of the conditioned stimulus

The present experiments were designed to test whether initial excitatory conditioning to a stimulus was obtained, using a within‐subject design of the truly random control (TRC) procedure, and to examine the effects of the density of the conditioned stimulus on it. In Experiment 1, the effect of the three levels of CS density (50%, 25%, 20%) was assessed at six different stages of training, using the conditioned suppression of licking in rats. Although all of the groups given the TRC procedure showed evidence of initial excitatory conditioning, it was more marked in the group with the highest CS density than in the other groups. Experiment 2 confirmed the results of Experiment 1, using a between‐subject design. The findings are in line with predictions from the Rescorla‐Wagner model, and are discussed with reference to other contemporary theories of associative learning.

The effects of CS intensity on the initial excitatory conditioning resulting from the truly random control procedure in rats

In the classical conditioning, the truly random control (TRC) procedure, in which conditioned stimuli (CS) and unconditioned stimuli (US) are presented independently, results in an excitatory conditioning in early part of training. The purpose of the present research was to examine an effect of CS intensity upon this initial excitatory conditioning effect. Both in Experiments 1 and 2, the TRC procedure, in which a tone was used as CS and an electric shock as US, was conducted using a technique of conditioned suppression of licking in rats. Suppression to the CS was assessed four times every fifth session of the TRC training. In Experiment 1, using relatively low CS-density, the group trained with a strong CS showed more suppression than the group trained with a moderate CS in the first test session. In Experiment 2, using relatively high CS-density, the group trained with a moderate CS and the group trained with a weak CS showed equivalent suppression in the first test session, but the suppression of the former group was long-lived. Although these results were consistent with the Rescorla-Wagner model as a whole, the interaction between the amount and the duration of the initial excitatory conditioning effect remained to be investigated in future research.

条件刺激と無条件刺激の負の随伴性の操作における2種類の方法とラットを用いた摂水反応の条件性抑制

条件刺激と無条件刺激の負の随伴性の操作における2種類の方法とラットを用いた摂水反応の条件性抑制

Erratum to: CS modality effects in one-trial backward and forward excitatory conditioning as assessed by conditioned suppression of licking in rats

Rats received a single 4-sec 1-mA grid-shock US either preceded or followed by a 4-sec tone or light CS. Conditioning was later assessed by comparing the amount of lick suppression evoked by the forward- or backward-paired CS versus an explicitly unpaired CS. The backward-paired CS produced more suppression than the unpaired CS only when both were tone; the light evoked strong suppression whether paired or not. In the forward procedure, tone produced more suppression when paired and less when unpaired than did light; conditioning thus appeared stronger with the tone. In one experiment, observations showed that rats froze during the forward-paired tone but not during the light. Increasing CS duration from 4 to 12 sec had no effect for the forward-paired light but increased freezing to the forward-paired tone. Another experiment showed similar unconditioned suppression to tone and light but faster habituation to tone. Problems that these results create for interpreting evidence for excitatory backward conditioning in the conditioned suppression procedure are discussed.

CS modality effects in one-trial backward and forward excitatory conditioning as assessed by conditioned suppression of licking in rats

Rats received a single 4-sec 1-mA grid-shock US either preceded or followed by a 4-sec tone or light CS. Conditioning was later assessed by comparing the amount of lick suppression evoked by the forward- or backward-paired CS versus an explicitly unpaired CS. The backward-paired CS produced more suppression than the unpaired CS only when both were tone; the light evoked strong suppression whether paired or not. In the forward procedure, tone produced more suppression when paired and less when unpaired than did light; conditioning thus appeared stronger with the tone. In one experiment, observations showed that rats froze during the forward-paired tone but not during the light. Increasing CS duration from 4 to 12 sec had no effect for the forward-paired light but increased freezing to the forward-paired tone. Another experiment showed similar unconditioned suppression to tone and light but faster habituation to tone. Problems that these results create for interpreting evidence for excitatory backward conditioning in the conditioned suppression procedure are discussed.

One-trial excitatory backward conditioning as assessed by conditioned suppression of licking in rats: Concurrent observations of lick suppression and defensive behaviors

Twenty-eight male albino rats were given a single 4-sec 1-mA electric-grid-shock unconditioned stimulus (US). In the same session they received two 12-sec conditioned stimuli (CSs). One CS (explicitly unpaired) terminated 180 sec before the US began; the other (backward paired) began immediately after the US terminated. The CSs used were a 1000-Hz 85-dB tone and an 84-dB click; their roles were counterbalanced. Over the next 2 days, each CS was presented for 2 min while the rats drank from a water bottle. The backward-paired CS was found to suppress licking more than the explicitly unpaired CS. This suppression was accompanied by an increase in defensive behavior (freezing and freeze/nod) and by a decrease in other activity. The suppression did not seem to be due to a maintained or enhanced CS-orienting response reflex, nor could it be attributed to an adventitiously reinforced interfering operant. The results support the presumption made in previous reports that the lick suppression evoked by a backward CS reflected one-trial backward excitatory fear conditioning.

A Re-Examination of One-Trial Blocking in Conditioned Suppression

Three experiments on the conditioned suppression of licking in rats examined the amount of conditioning produced by a single conditioning trial to a clicker-light compound and the effect of prior conditioning to the light on the level of conditioning to the clicker. In Experiment I, prior conditioning to the light, far from blocking conditioning to the clicker, actually enhanced it, whether the clicker was presented in a simultaneous compound with the light or in a serial compound preceding the light. Experiment II, however, showed that this potentiation effect could be abolished if a trace interval was inserted between the clicker and light in the serial compound arrangement. Moreover, Experiment III demonstrated a significant blocking effect when a trace interval separated the clicker and light on the single compound trial. These results establish that one-trial blocking of conditioned suppression is possible, and suggest that in some earlier studies blocking may have been masked by higher-order conditioning to the target stimulus.

One-trial overshadowing: Evidence of distributive processing.

Evidence of "overshadowing" following a single training trial was obtained in each of five experiments measuring stimulus-evoked suppression of licking in rats. In three conditioned emotional response experiments, less conditioned suppression was observed to either a light or a tone when the stimuli had been paired with shock in compound that when either had been paired with shock in isolation. This difference occurred when the stimuli were diffuse and produced differential orienting behaviors on the training trial (Experiment 1). But, it was as demonstrable when the stimuli were designed to be localizable from the same source and produce apparently compatible orienting behaviors (Experiments 2A and 3A). The difference was also as substantial when the stimulus compound was composed of successive, nonoverlapping stimulus elements as when composed of simultaneous elements (Experiment 3A). In two companion habituation studies (Experiments 2B and 3B) using the same stimulus arrangements but no pairing with shock, there was consistently less habituation of the unconditioned suppression to the visual and tonal stimuli when exposed in compound rather than in isolation. One-trial "overshadowing" is at odds with those theories that approach overshadowing only as a multiple-trial phenomenon. The apparent generality of the effect provides impetus for a theoretical account that supposes some manner of distributive processing.

One-trial overshadowing: Evidence of distributive processing.

Evidence of "overshadowing" following a single training trial was obtained in each of five experiments measuring stimulus-evoked suppression of licking in rats. In three conditioned emotional response experiments, less conditioned suppression was observed to either a light or a tone when the stimuli had been paired with shock in compound that when either had been paired with shock in isolation. This difference occurred when the stimuli were diffuse and produced differential orienting behaviors on the training trial (Experiment 1). But, it was as demonstrable when the stimuli were designed to be localizable from the same source and produce apparently compatible orienting behaviors (Experiments 2A and 3A). The difference was also as substantial when the stimulus compound was composed of successive, nonoverlapping stimulus elements as when composed of simultaneous elements (Experiment 3A). In two companion habituation studies (Experiments 2B and 3B) using the same stimulus arrangements but no pairing with shock, there was consistently less habituation of the unconditioned suppression to the visual and tonal stimuli when exposed in compound rather than in isolation. One-trial "overshadowing" is at odds with those theories that approach overshadowing only as a multiple-trial phenomenon. The apparent generality of the effect provides impetus for a theoretical account that supposes some manner of distributive processing.

CS and US duration effects in one-trial simultaneous fear conditioning as assessed by conditioned suppression of licking in rats

In three experiments, rats received a single presentation of an auditory conditioned stimulus (CS) beginning simultaneously with an electric grid-shock unconditioned stimulus (US). Later, the CS was presented while the rats licked a drinking tube for water, and CS-elicited suppression of licking was taken as an index of the excitation conditioned to the CS. It was found that conditioning increased as a joint function of the duration of CS-US overlap and US duration. The evidence suggested that weak conditioning due to a brief CS-US overlap could be increased by extending the US beyond CS termination. Extending CS duration beyond US termination, however, did not strengthen conditioning; indeed, extending the CS 60 sec beyond US termination weakened conditioning significantly. It is suggested that these results shed light on a discrepancy in the recent literature on simultaneous conditioning.

One-trial simultaneous and backward fear conditioning as reflected in conditioned suppression of licking in rats

In three experiments, groups of albino rats received one strictly simultaneous pairing of a 4-sec auditory conditioned stimulus (CS) and a 4-sec 1-mA shock unconditioned stimulus (US). Other groups received a backward pairing, in which the US began before the CS, or a forward pairing, in which the CS began before the US. Control groups received only the US or received both the CS and the US but widely separated in time. Later, the CS was presented while the rats licked a drinking tube for water, and CS-elicited suppression of licking was taken as an index of the Pavlovian conditioned response (CR). It was found that groups receiving a single forward or a single simultaneous pairing suppressed more than groups that had received a backward pairing; and the backward groups, in turn, suppressed more than the control groups. It appears, then, that excitatory fear conditioning, as reflected in conditioned suppression of licking in rats, can be produced in a single trial by both backward and simultaneous conditioning procedures.