Rabbit Nictitating Membrane Preparation Research Articles

Two streams make a river: The rabbit in Richard F. Thompson’s laboratory

The rabbit nictitating membrane (NM) preparation was developed in 1962 by Gormezano as a model system for classical conditioning. It had many features that made it ideal for use in exploring the laws of this conditioning paradigm, including easily obtainable subjects, good control of stimulus delivery and precise response specifications. Most importantly, the preparation evidenced very low spontaneous response rates and showed no evidence of nonassociative effects of sensitization and pseudoconditioning and had highly predictable learning functions. In contrast, previous human and animal models that had been utilized to explore the features of classical conditioning, such as the dog salivary model were far less easy to use, showed high spontaneous response rates, and had high nonassociative components. Over the ensuing years, Gormezano and his students characterized most of the parametric characteristics of classical conditioning with the use of the preparation. In 1970, Richard Thompson began exploring the use of the rabbit NM preparation in his laboratory as a model system with which to explore the brain substrates of classical conditioning. At the time, his work was centered around exploring the neural substrates of sensitization and habituation in spinal reflexes. Soon, however, he turned his attention to the brain substrates of classical conditioning almost exclusively, and produced an impressive amount of data detailing the neural underpinnings of classical conditioning. His work has generated perhaps the most detailed and complete picture of the neural mechanisms of learning currently available, and has led to countless other research efforts in the area of brain and behavior. Current understandings of neural mechanisms of associative learning owe much to Thompson and his various colleagues.

Time and stimulus specificity in extinction of the conditioned nictitating membrane response in the rabbit (Oryctolagus cuniculus).

The present experiments demonstrated that, in the rabbit nictitating membrane preparation, a conditioned response (CR) can be selectively eliminated in one portion of a conditioned stimulus (CS) while it is still paired with the unconditioned stimulus (US). Rabbits were initially trained with two stimuli (tone, light). Each was paired with the US by using a mixture of two CS-US interstimulus intervals (ISIs): 200 ms and 1,200 ms in Experiment 1; 150 ms and 500 ms in Experiment 2. The CRs showed double peaks, one for each ISI. Subsequently, one CS (A) was trained with only the longer ISI, whereas the other CS (B) continued to be trained with both ISIs. Consequently, the CR peak based on the shorter ISI disappeared for CSA but not for CSB. The later CR peaks during both CSA and CSB were maintained. These results support time-based models of conditioning. Implications for proposed mechanisms of extinction are discussed.

Savings after extinction in conditioning of the rabbit’s nictitating membrane response

The present experiments examined two forms of savings after the extinction of a conditioned response (CR) in the rabbit nictitating membrane preparation. Each experiment entailed three groups. First, a reacquisition (RAQ) group received initial conditioned stimulus-unconditioned stimulus (CS—US) acquisition, followed by CS-alone extinction, and then CS—US reacquisition with the same stimulus. Second, a cross-modal acquisition (CMA) group received initial acquisition and extinction with one stimulus but received its final stage of training with a stimulus from another modality. Third, a naive acquisition group (designated as REST) received only the final stage of CS—US training. In all three groups, tone and light were used as CSs in a counterbalanced fashion. In addition, the experiments tested whether the manipulation of contextual factors—namely, trial spacing and the number of trials per session—could influence the rates of acquisition in Groups RAQ and CMA after extinction. The experiments demonstrated that (1) reacquisition of the CR to the original CS was very rapid relative to Group REST, (2) cross-modal acquisition was also rapid relative to Group REST, and (3) in Group CMA, tests of the original CS showed concurrent recovery, which is a new phenomenon and is distinct from spontaneous recovery. However, the relative rates of acquisition after extinction appeared constant across the contextual manipulations. The results are discussed with respect to the relative stability of excitatory and inhibitory learning, as well as two alternative theories of savings after extinction.

Within-stimulus competition in trace conditioning of the rabbit’s nictitating membrane response

In four experiments, it was shown that the onset and offset of a tone conditioned stimulus (CS) in trace conditioning interact in much the same way as a sequence of two stimuli from different sensory sources, such as a tone and a light. The duration of the tone was manipulated across values ranging from 400 to 30,000 msec, whereas the trace interval between the tone offset and the US was fixed at 400 msec. The rate and level of total CR acquisition were high and constant across all tone durations. Likewise, responding during the trace interval on paired trials was relatively constant. However, when the tone onset and tone offset were tested in relative isolation from each other on test trials using a 30,000-msec tone, there was a reciprocal relationship in responding to tone onset and tone offset. When training had been conducted with shorter tone durations, responding to tone onset was only moderate but, nonetheless, higher than responding to tone offset, which was negligible. At the longer tone durations, responding to tone onset declined to lower levels, whereas responding to tone offset rose to a high level equal to the total level of responding. These effects were consistent across manipulations of tone intensity and prior delay conditioning, in which only tone onset could function as a CS. Consequently, the trace CS appears to act as a compound stimulus that engages complex associative processes as well as simple associative processes. The implications of the present results for understanding the susceptibility of trace conditioning to hippocampal damage in the rabbit nictitating membrane preparation are discussed.

MK-801 protects conditioned responses from extinction in the rabbit nictitating membrane preparation

MK-801 is a noncompetitive antagonist to N-methyl-d-aspartate (NMDA) receptors. MK-801 was given (0.05 or 0.10 mg/kg i.v.) to rabbits during extinction of a well-established conditioned response (CR) in the nictitating membrane preparation. The drug administration produced an immediate deficit in CR performance during extinction. However, when MK-801 administration was suspended, CRs reappeared immediately and showed no evidence of the previous extinction treatment. In addition, we confirmed previous findings that MK-801 impairs both the acquisition and the expression of CRs during CS—US training. A reduction in CS processing caused by MK-801 is the most parsimonious explanation of the data. There are also two-factor alternatives, which contend that MK-801 directly hinders associative formation and either directly blocks CR output or produces a state-dependent generalization decrement.

MK801 impairs acquisition and expression of conditioned responses in the rabbit nictitating membrane preparation

MK801 is a noncompetitive antagonist to N-methyl-D-aspartate (NMDA) receptors. MK801 (0.1 mg/kg IV) was given to rabbits during classical conditioning of their nictitating membrane response. Administration of MK801 before each training session impaired acquisition of a conditioned response (CR). When MK801 administration was suspended, responding remained at a low level. Control animals were given either MK801 after each training session (Experiment 1) or saline before each session (Experiment 2). The control animals showed high levels of CR acquisition. When the control animals were given the MK801 before a session, they showed a large deficit in responding. Responding returned to its former level when the original control condition was reinstated. In all the animals, tests for motor deficits caused by MK801 proved negative; the magnitude of the UR was not influenced by MK801 at either the beginning or end of training. In conclusion, it appears that MK801 impairs both the formation of associative linkages and the performance of established CRs. A reduction in CS salience caused by MK801 is the most parsimonious explanation of the data. There is a more complex, two-factor alternative that contends that MK801 directly hindered associative formation in the subjects trained with that drug and produced a state-dependent generalization decrement in responding when introduced to the control subjects.

Classical conditioning of the rabbit nictitating membrane response can be fast or slow: Implications for Lennartz and Weinberger’s (1992) two-factor theory

Classical conditioning of the rabbit’s nictitating membrane (NM) response usually requires several dozen trials for the first conditioned response (CR) to appear. However, as the number of trials is reduced to one per session, the rate of acquisition increases progressively, and the first CR appears in less than a dozen trials. This large and systematic variation in the rate of conditioning challenges recent conclusions by Lennartz and Weinberger (1992). They use the rabbit NM preparation as an example of a slow-conditioning, “specific” system that is distinct from a fast-conditioning, “nonspecific” system, such as heart rate.

Erratum to: Laws of the unconditioned reflex in the rabbit nictitating membrane preparation

Erratum to: Laws of the unconditioned reflex in the rabbit nictitating membrane preparation

Laws of the unconditioned reflex in the rabbit nictitating membrane preparation

The unconditioned response (UR) of the rabbit’s nictitating membrane (NM) was examined as a function of the intensity and duration of electrotactile and airpuff unconditioned stimuli (USs). For both USs, increases in US intensity produced increases in UR likelihood and amplitude, and decreases in onset latency. Increases in US duration had similar but smaller effects on the UR. The peak latency of the UR was also examined, but it proved to be highly variable. The data were analyzed by using progressively larger NM movements to define a UR. The lower criteria of 0.125, 0.250, and 0.500 mm produced virtually identical results. The more stringent criteria of 0.750, 1, and 2 mm produced decreases in the observed UR likelihood, increases in apparent UR amplitude, and increases in apparent peak latency.

Rapid reaquisition in conditioning of the rabbit's nictitating membrane response.

Reacquisition after extinction often appears faster than original acquisition. However, data from conditioned suppression studies indicate that this effect may arise from spontaneous recovery and reinstatement of unextinguished contextual stimuli related to the unconditioned stimulus (US). In the present experiments using the rabbit nictitating membrane preparation, spontaneous recovery was eradicated before reaquisition training. US contextual stimuli were controlled by retaining the US during extinction through explicit unpairings of the conditioned stimulus (CS) and US. Attempts were also made to drive the associative strength of the CS into the inhibitory region by differential conditioning and conditioned inhibition procedures. In all cases, reacquisition was very rapid in comparison with a rest control. The results are discussed with respect to their implications for CS and US processing models of conditioning.

Trace conditioning of the rabbit's nictitating membrane response as a function of CS-US interstimulus interval and trials per session

The present experiment examined modification of URs and acquisition of CRs in the rabbit's nictitating membrane preparation as a function of the CS-US interstimulus interval (ISIs = 400, 800, 1600, and 3200 ms) and trials per session (1, 5, and 25). In both paired CS-US groups and corresponding unpaired groups ( n = 12), UR amplitude was greater under 1 and 5 trials per session than under 25 trials per session. In early CR acquisition, ISI interacted with trials per session such that CRs emerged rapidly for all ISIs under 1 and 5 trials per session but emerged more slowly as an inverse function under 25 trials per session. Later in training, CR frequency tended to be inversely related to ISI under 1, 5, and 25 trials, but training under 1 and 5 trials per session differentially raised the asymptotic CR frequency at the longer ISIs, especially the 3200-ms value. The results are discussed in terms of their implications for accounts of trial spacing effects and the time course of CS representations in trace conditioning.

Retention and acquisition of classical trace conditioned responses by rabbits with hippocampal lesions.

The effects of dorsal hippocampal lesions on retention of classical trace conditioned responses were examined using the rabbit nictitating membrane preparation. Animals were trained to criteria and then lesioned either in the cortex or in the hippocampus and the cortex. Hippocampal damage had no effect on the retention of responses but produced significantly longer onset latencies. A control group of hippocampal animals acquired conditioned responses (CRs) at least as quickly as the prelesion subjects, and they also exhibited longer response onset latency. A second experiment evaluated the performance of hippocampal lesioned animals in classical trace conditioning with either a low-intensity periorbital shock or corneal air puff as the unconditioned stimulus (UCS). Hippocampal animals successfully acquired CRs under both conditions but exhibited an alteration of response onset which was dependent on the form of the UCS. Hippocampal animals displayed shorter response onset in the air-puff condition and longer response onset in the shock condition. Cortical animals timed responses consistently regardless of the UCS. These findings strongly suggest that the hippocampus modulates temporal characteristics of learned behavior.

Auditory sensitivity in the rabbit determined by a conditional nictitating of membrane response

Auditory sensitivity was measured in New Zealand white rabbits trained by means of a behavioral technique utilizing classical conditioning of the nictitating membrane (NM) response. Conditioning trials consisted of the presentation of a 350 msec pure tone stimulus of which the final 100 msec overlapped with the occurrence of a shock to the posterior orbital region. A conditioned NM response was defined as a 0.5 mm deflection with a latency ranging from 130 to 260 msec following tone onset. Threshold and latency‐intensity functions were collected from 500 Hz to 32 kHz using the method of constant stimuli under closed field conditions. Animals were most sensitive to test stimuli between 8 and 16 kHz with maximum sensitivities at sound pressure levels ranging from −1 to 11 dB SPL. For frequencies above 16 kHz and below 3 kHz, sensitivity rapidly decreased. The latency of the NM response was found to be an inverse function of stimulus intensity over a fairly large dynamic range similar to the latency‐intensity functions obtained with operant reaction‐time tasks. A number of features will be discussed that make the rabbit NM preparation a highly desirable behavioral and/or neurophysiological model for studying auditory phenomena.